Nervous and humoral regulation of body functions. Human central nervous system What underlies the nervous regulation of functions

Regulation objectives:

1. Maintaining homeostasis.

Types of regulation:

Out of outrage.

By deviation.

Proactively.

Basic mechanisms of regulatory influences in the body.

1.Self-regulation;

2. Nervous regulation;

3. Humoral regulation.

Self-regulation is carried out on the basis of feedback, which can be:

-positive feedback(The result of the reaction strengthens the process that forms this result.)

-negative feedback.( The result of the reaction inhibits the process that forms this result.)

Self-regulation is aimed at homeostasis of the activity of an organ or organ system.

Nervous regulation is carried out through the somatic nervous system and the autonomic nervous system.

Humoral regulation is carried out due to chemicals found in biological media (blood, lymph, intercellular fluid). These substances are called biologically active substances (BAS), they interact with membrane receptors.

Elements of the regulatory system:

1.Central element: CNS, system of endocrine glands.

2.Input channels: afferent nervous system, sensitive elements - receptors of nerve endings; sensors for humoral factor systems are cell membrane receptors.

3.Output channels: Nerve output channels (axons), output signals also spread through the humoral route.

Types of regulatory influences:

1. Trigger influence - Regulatory the system starts the function.

2. Corrective influence– Impact on current function.

3.Metabolic influence–An effect in which metabolism changes primarily, and function changes secondarily.

4. Morphogenetic influence. The structure changes primarily, the function changes secondarily.

Reflex activity of the central nervous system.

The basis of the nervous regulation of functions are reflexes.

Central inhibition can be primary or secondary.

Primary inhibition-inhibition that occurs without prior excitation. At the level of cellular mechanisms there are:

-Presynaptic inhibition. The inhibitory synapse is formed with the presynaptic membrane. Inhibitory mediators—GABA, glycine—are released at the synapse, which cause hyperpolarization of the presynaptic membrane;

-Postsynaptic inhibition. The inhibitory synapse is formed with the postsynaptic membrane. Inhibition of the postsynaptic membrane develops according to the type of cathodic depression.

Secondary central inhibition. This is inhibition that occurs after the primary excitation and is initiated by it.

Types of secondary braking:

a) beyond occurring when there is a large flow of information entering the cell. The flow of information lies beyond the functionality of the neuron;

b) pessimal, which occurs with a high frequency of irritation;

c) parabiotic, arising from strong and long-lasting irritation;

d) inhibition following excitation, arising as a result of a decrease in the functional state of neurons after excitation;

e) inhibition according to the principle of negative induction;

E) inhibition of conditioned reflexes.

Types of central inhibition in nerve networks.

Reciprocal inhibition.

Excitation of one group of efferent neurons through interneurons /Renshaw cells/ causes inhibition of another group of efferent neurons.

Return braking.

An efferent neuron often sends one of its axon collaterals to inhibitory interneurons, and they close their processes (axons) to the efferent cell.

Lateral inhibition.

Excitation of one group of afferent neurons through intercalary inhibitory neurons causes inhibition of another group of afferent neurons.

Braking zone.

Excitation in a group of main efferent neurons through intercalary inhibitory neurons causes inhibition of other efferent cells located nearby and at that moment receiving information from other afferent sources.

Tissue hormone system.

1)Serotin(intestinal mucosa, brain, platelets).

Effect: CNS mediator, vasoconstrictor effect, vascular-platelet hemostasis.

2) Prostaglandins(derivative of arachidonic and linolenic acid, body tissue). Effect: vasomotor effect: dilator and constrictor effect, increase uterine contractions, increase the excretion of water and sodium, reduce the secretion of enzymes and HCl by the stomach.

3) Bradikin(Peptide, blood plasma, salivary glands, lungs).

Effect: vasodilator effect, increases vascular permeability.

4) Acetylcholine(brain, ganglia, neuromuscular synapses).

Effect: relaxes the smooth muscles of blood vessels, reduces heart contractions.

5)Histamine(histidine derivative, stomach and intestines, skin, mast cells, basophils). Effect: mediator of pain receptors, dilates microvessels, increases the secretion of gastric glands.

6) Endorphins, enkephalins(brain).

Effect: analgesic and adaptive effects.

7) Gastrointestinal hormones(produced in various parts of the gastrointestinal tract).

Effect: participate in the regulation of the processes of secretion, motility and absorption.

Anterior lobe of the pituitary gland.

All hormones of the anterior lobe are substances of protein nature (peptides, proteins, glycoproteins).

Gonadotropic hormones.

Gonadotropic hormones include follicle-stimulating hormone (FSH) and luteinizing hormone (LH) of the pituitary gland. When the anterior lobe of the pituitary gland is removed, atrophy of the gonads is observed.

In women, FSH stimulates the maturation of follicles in the ovaries. This process is completely carried out in the presence of PH.

Luteinizing hormone (LH) stimulates the ovulation process. In the second half of the cycle, LH stimulates the development of the corpus luteum in the ovaries.

In men, FSH stimulates the development of seminiferous tubules, spermatogenesis and prostate growth.

LH is necessary for the formation of male sex hormones.

The type of secretion of FSH and LH in men is tonic, in women it is cyclic. FSH and LH are not sex specific.

Regulation: folliberin and luliberin.

Adrenocorticotropic hormone (ACTH).

ACTH is a polypeptide. The point of application of ACTH is the fascicular and, to a lesser extent, the zona glomerulosa of the adrenal cortex.

The secretion of ACTH by the pituitary gland increases when exposed to all extreme stimuli that cause a state of tension in the body.

ACTH, acting on the adrenal glands, causes increased production of glucocorticoids, and also, to a small extent, mineralocorticoids.

By regulating the production and release of glucocorticoids, ACTH indirectly causes the same effects (participates in stress mechanisms, stimulates the breakdown of proteins to amino acids, glycogen to glucose, inhibition of protein synthesis, increased breakdown of fats), i.e. has a catabolic effect.

Regulated by: the level of adrenaline in the blood (trigger factor); corticoliberin.

Vasopressin is a pituitary antidiuretic hormone (ADH).

The point of application of the hormone is the distal convoluted tubules and collecting ducts of the nephron. Includes the transport protein aquaporin-2 in the membrane, which forms a channel for facilitated diffusion of water and enhances the reabsorption of water in the kidneys, i.e. inhibits diuresis. As a result, BCC and blood pressure increase. Vasopressin is a pituitary antidiuretic hormone (ADH):

Stimulates the thirst center, participates in the mechanisms of memory, thermoregulation, and emotional behavior.

In its absence, diabetes insipidus syndrome (diabetes insipidus) develops.

At higher concentrations, it increases the tone of the smooth muscles of muscular-type vessels (arterioles), increasing blood pressure.

Regulation:

Nerve impulses from hypothalamic cells;

Based on the principle of negative feedback (decrease in blood volume and the level of the hormone itself).

Oxytocin.

Causes rhythmic contraction of the uterus, promoting the normal course of labor; increases the contractile activity of the excretory ducts of the mammary gland, promoting lactation in the postpartum period.

At the end of pregnancy and after childbirth, the concentration of the hormone in the bloodstream increases significantly, the sensitivity of smooth muscles to it also increases, and is involved in forgetting mechanisms.

Regulation: based on the feedback principle, reflexively (if the areolas are irritated during feeding).

Stimulating

Braking

-According to the mechanism of action on target cells

1. Acting through membrane receptors(Lipophobic) - Soluble in water. (Hormones of the hypothalamus and pituitary gland)

2. Acting via intracellular receptors(Lipophilic) - Soluble in fats. (Sex hormones)

Parahormones-BAS produced by specialized cells have an effect mainly at the site of production.

The main functions of hormones:

1.Metabolic function of hormones(Effect on metabolism)

2. Corrective function of hormones(Regulation of the current activities of individual body systems and their functions)

3.Kinetic function of hormones(Enable functions)

Types of functional influence of hormones:

Trigger influence

The ability of a hormone to trigger the activity of an effector.

Modulating influence

Changes in the intensity of organ activity, changes in tissue sensitivity to the action of other hormones.

Permissive influence

The ability of one hormone to ensure the implementation of the effect of another hormone.

Mechanisms of action of hormones. Concepts about organs and target cells, cellular receptors. Formation of a hormonal response at the cellular level. Hormone-receptor complex. Secondary intermediaries. Differences in the mechanism of action of steroid and protein hormones.

Mechanisms of action of hormones:

1) If the cell membrane is impermeable to the hormone (hormones of the pituitary gland and hypothalamus), then the receptors are located in the membrane itself.

The hormone receptor complex of these hormones activates intracellular processes leading to the formation of second messengers, which realize their action mainly through the nuclear apparatus of the cell.

Mineralocorticoids.

These include aldosterone (the most active) and deoxycorticosterone.

Effects of mineralocorticoids:

1.Increases the reabsorption of sodium and chlorine in the renal tubules.

2. Reduces potassium reabsorption in the renal tubules.

Glucocorticoids.

These include cortisol (the most active), corticosterone, hydrocortisone.

Effects of glucocorticoids:

1.Participation in the formation of stress reactions, participation in immediate and long-term adaptation, Increased sensitivity to catecholamines.

2. Anti-inflammatory effect.

3. Weakening the action of the immune system, reducing the content of lymphocytes and basophils in the blood.

4.Increased blood glucose levels. Increased formation and deposition of glycogen in the liver and tissues. Decreased insulin sensitivity. A decrease in the permeability of cell membranes of a number of tissues for glucose prevents its entry into the tissue.

5. Stimulates protein catabolism and inhibits protein anabolism (anti-anabolic effect), reducing the permeability of cell membranes to amino acids.

6. Strengthening the mobilization of fat from fat depots.

Sex hormones.

These include androgens, estrogens and progesterone.

They play an important role in the development of secondary sexual characteristics in childhood. When puberty is reached, the role of hormones is small. Hormones again acquire some importance in old age - after the extinction of the function of the gonads.

Physiological effects.

They depend on what type of adrenergic receptors predominates in a particular structure.

Excitation alpha adrenergic receptors calls:

Narrowing of small arterial vessels of the skin and abdominal organs;

Increased blood pressure;

Contraction of the uterus;

Pupil dilation;

Relaxation of smooth muscles of the stomach and intestines;

Inhibits secretion in the digestive tract;

Acceleration of platelet aggregation.

Excitation beta adrenergic receptors calls:

Increased and increased heart rate;

Stimulation of renin secretion;

Dilation of the bronchi;

Dilation of some arterial vessels (coronary);

Relaxation of the uterus.

Effects of insulin.

Insulin affects all types of metabolism, it promotes anabolic processes:

1. enhances the synthesis of glycogen, fats, proteins;

2. inhibits the effects of hormones that have a catabolic effect (catecholamines, glucocorticoids, glucagon, etc.).

The effects of insulin are divided into 4 groups according to the speed of implementation:

1.Very fast(after a few seconds). Increasing the permeability of cell membranes to glucose.

2.Quick effects(within a few minutes).

Activation of enzymes that enhance anabolic processes

Inhibition of enzymes responsible for catabolic processes.

3.Slow effects ( during few hours).

Increasing membrane permeability for amino acids;

Strengthening the synthesis of mRNA and enzymes for the synthesis of specific proteins.

4.Very slow effects(from hours to days). Activation of mitogenesis.

Peptide sex hormones.

Relaxin– produced by cells of the corpus luteum in the uterus. Its effect is to relax the pelvic ligaments. Its production increases during childbirth.

Inhibin– inhibits spermatogenesis during prolonged abstinence.

Thymus gland (thymus).

Plays a large role in ensuring the immunocompetence of T cells; the lymphatic system is formed under its influence.

A number of polypeptides have been isolated from the thymus - thymosin, thymopoietin, thymic humoral factor. Only thymosin has been studied.

Thymosin helps increase the body's reactivity, stimulates erythro- and lymphopoiesis. With an excess of thymosin, bone marrow hyperplasia may occur. Participates in the differentiation of T-lymphocytes and the formation of their immunocompetence.

Epiphysis

Melatonin is formed. The maximum secretion of melatonin occurs at night. Excess light inhibits the formation of melatonin.

Provides adaptation of the body to different lighting conditions. An increase in the concentration of melatonin in the blood inhibits the secretion of gonadotropins, corticotropin, thyrotropin, and somotropin.

Endocrine kidney function.

The kidneys produce three compounds that have hormonal activity: calcitriol, renin, erythropoietin.

Calcitriol– is an active metabolite of vitamin D3. Main effects:

1.activates the absorption of calcium and phosphates in the intestines;

2.activates the reabsorption of calcium and phosphates in the kidney tubules;

3.stimulates osteoblasts.

Renin– is formed in the juxtaglomerular apparatus of the kidneys (JRA).

Renin is an enzyme that in plasma causes the breakdown of the protein angiotensinogen and the formation of angiotensin I, which has no physiological activity, is exposed to the action of angiotensin-converting enzyme, and angiotensin II is formed, which has high physiological activity. Cell membranes contain receptors for angiotensin - angiotensin receptors.

Effects of Angiotensin II:

1. Causes a strong contraction of arterioles and small arteries.

2. Stimulates the secretion of aldosterone by the zona glomerulosa of the adrenal glands.

3.Increases blood pressure.

There is a single renin-angiotensin-aldosterone system, which is an important regulator.

Endocrine function of the heart.

Atrial myocytes secrete a regulatory peptide - atriopeptide or atrial natriuretic hormone.

Physiological effects:

Vascular effects:

1. Relaxation of vascular smooth muscles (vasodilation).

2.Decreased blood pressure.

Renal effects:

1. Suppression of reabsorption of sodium and chlorine in the tubules.

2.Powerful increase in the excretion of sodium (90 times) and chlorine (50 times).

General principles of regulation of functions. Reflex activity of the central nervous system. Nerve center, properties of nerve centers, features of excitation through nerve centers.

Physiological regulation (regulation of functions) - This is the active management of body functions to ensure the constancy of the internal environment of the body required for this metabolism in order to adapt to changed environmental conditions.

Regulation objectives:

1. Maintaining homeostasis.

2.Providing energy and information.

Types of regulation:

Out of outrage.

Occurs when an external factor influences the body, changing the conditions of its existence. This type of regulation refers to adaptive regulation.

By deviation.

Deviation of one or more parameters of the internal environment initiates regulatory influences aimed at normalizing indicators of the internal environment. This type of regulation refers to homeostatic regulation.

Proactively.

Based on information extracted from memory, a behavioral reaction is formed that anticipates the actual action.

A1. Nervous regulation is based on

1) electrochemical signal transmission

2) chemical signal transmission

3) mechanical signal propagation

4) chemical and mechanical signal transmission

A2. The central nervous system consists of

1) brain

2) spinal cord

3) brain, spinal cord and nerves

4) brain and spinal cord

A3. The elementary unit of nervous tissue is

1) nephron 2) axon 3) neuron 4) dendrite

A4. The place where a nerve impulse is transmitted from neuron to neuron is called

1) neuron body 3) nerve ganglion

2) nerve synapse 4) interneuron

A5. When the taste buds are stimulated, saliva begins to be released. This reaction is called

1) instinct 3) reflex

2) habit 4) skill

A6. The autonomic nervous system regulates activity

1) respiratory muscles 3) cardiac muscles

2) facial muscles 4) limb muscles

A7. Which part of the reflex arc transmits the signal to the interneuron?

1) sensory neuron 3) receptor

2) motor neuron 4) working organ

A8. The receptor is stimulated by a signal received from

1) sensitive neuron

2) interneuron

3) motor neuron

4) external or internal stimulus

A9. Long processes of neurons unite into

1) nerve fibers 3) gray matter of the brain

2) reflex arcs 4) glial cells

A10. The mediator ensures the transmission of excitation in the form

1) electrical signal

2) mechanical irritation

3) chemical signal

4) sound signal

A11. During lunch, a motorist's car alarm went off. Which of the following can happen at this moment in the cerebral cortex of this person?

1) excitation in the visual center

2) inhibition in the digestive center

3) excitement in the digestive center

4) inhibition in the auditory center

A12. When a burn occurs, excitement occurs

1) in the bodies of executive neurons

2) in receptors

3) in any part of the nervous tissue

4) in interneurons

A13. The function of interneurons of the spinal cord is

D. A. Sakharov.

Great Soviet Encyclopedia. - M.: Soviet Encyclopedia. 1969-1978 .

See what “Nervous regulation” is in other dictionaries:

The coordinating influence of the nervous system (NS) on cells, tissues and organs, bringing their activities into line with the needs of the body and changes in the environment; one of the main mechanisms of self-regulation of functions. Multicellular organism... ... Wikipedia

The regulatory effect of the nervous system on tissues, organs and their systems, ensuring the consistency of their activities and the normal existence of the organism as a whole in changing environmental conditions. See Neurohumoral regulation... Big Encyclopedic Dictionary

The coordinating influence of the nervous system on cells, tissues and organs, bringing their activity into line with the needs of the body and changes in the environment. N. r. has a leading role in ensuring the integrity of the body and is... ... Biological encyclopedic dictionary

The regulatory effect of the nervous system on tissues, organs and their systems, ensuring the consistency of their activities and the normal existence of the organism as a whole in changing environmental conditions. See Neurohumoral regulation. * * * NERVOUS… … encyclopedic Dictionary

neural regulation- nervinis reguliavimas statusas T sritis Kūno kultūra ir sportas apibrėžtis Nervų sistemos veikla, koordinuojanti fiziologinius organizmo vyksmus. atitikmenys: engl. nervous regulation vok. Nervenregulation, f rus. nervous regulation...Sporto terminų žodynas

Regulatory influence of nerves. systems on tissues, organs and their systems, ensuring the consistency of their activities and the normal existence of the organism as a whole in changing environmental conditions. See Neurohumoral regulation... Natural science. encyclopedic Dictionary

NERVOUS REGULATION- [from lat. regulare put in order, establish] the regulatory effect of the nervous system on tissues, organs and their systems, ensuring the consistency of their activities and the normal existence of the organism as a whole in changing environmental conditions... ... Psychomotorics: dictionary-reference book

nervous system- (from the Greek n e u gop nerve and sistema whole, made up of parts) the totality of all elements of the nervous tissue of living organisms, interconnected and providing a response to external and internal stimuli. N. s. provides... ... Great psychological encyclopedia

Filtering of sensory information; filtering of afferent signals by the nervous system. As a result of such filtering, only part of the sensory information received by previous levels is received at certain processing levels. In English... ... Wikipedia

A complex network of structures that permeates the entire body and ensures self-regulation of its vital functions due to the ability to respond to external and internal influences (stimuli). The main functions of the nervous system are receiving, storing and... Collier's Encyclopedia

Books

• Physiology and ethology of animals. Textbook and workshop. In 3 parts. Part 3. Endocrine and central nervous systems, higher nervous activity, analyzers, ethology, A. I. Enukashvili, A. B. Andreeva, T. A. Eisymont. This textbook is a presentation of the basic physiological functions of the body. Focusing on modern scientific data, the authors revealed the essence of the mechanisms of nervous, humoral and... Series: Vocational education Publisher: YURAYT, Manufacturer:

The body functions as a single whole. There are two ways to regulate the body's activity: nervous and humoral.
Humoral (fluid) regulation carried out with the help of chemicals (hormones, mediators, ions, metabolic products) through the liquid media of the body (blood, lymph, intercellular fluid). Humoral regulation is carried out with the help of biologically active substances. Biologically active substances are chemical substances, very small concentrations of which can have a significant physiological effect.

Glands- special organs that produce biologically active substances.

Exocrine glands secrete substances into body cavities, organs, or onto the surface of the skin through special ducts (tear, sweat, salivary, stomach glands, etc.). Endocrine glands secrete substances into the blood and lymph flowing through them (pituitary gland, thyroid gland, adrenal glands, etc.).

Biologically active substances secreted by the endocrine glands are called hormones. Mixed glands perform exocrine and intrasecretory functions (pancreas and gonads).
Nervous regulation carried out using nerve impulses along the membranes of nerve cells. This is an evolutionarily later method of regulation. It is faster and more accurate.
In the body, the mechanisms of nervous and humoral regulation closely interact with each other and are carried out simultaneously. They complement each other and have mutual influence. That's why they talk about neurohumoral regulation body. For example, a decrease in blood glucose levels causes stimulation of the sympathetic nervous system. This stimulates the adrenal glands to release adrenaline, which enters the liver through the bloodstream, causing the breakdown of glycogen there into glucose. Glucose enters the blood, its content in the blood is normalized.
A feature of the body is the ability to self-regulate. Self-regulation- maintaining all vital parameters of the body (blood pressure, body temperature, blood sugar, etc.) at a relatively constant level. Neurohumoral regulation ensures the interrelation and coordinated work of all organ systems. Therefore, the body functions as a single whole.

Nervous system

The nervous system carries out the interconnection of all parts of the body (nervous regulation), its relationship with the environment and conscious human activity. The activity of the nervous system underlies the processes of higher nervous activity (feelings, learning, memory, speech, thinking, etc.).
The nervous system is anatomically divided into central(brain and spinal cord) and peripheral(nerves and ganglia). Depending on the nature of the innervation of organs and tissues, the nervous system is divided into somatic(controls the activity of skeletal muscles and obeys the will of a person) and vegetative(autonomous) (controls the activity of internal organs, glands, smooth muscles and is not subject to human will).

Reflexes

All acts of conscious and unconscious activity are reflex acts.

Reflex- the body's response to irritation carried out by the central nervous system.

Reflex arc- the path along which nerve impulses pass from the receptor to the working organ.

From the receptor to the central nervous system, impulses travel along the sensory path, and from the central nervous system to the working organ along the motor path. The reflex arc has the following components: receptor(end of the dendrite of a sensory neuron; perceives irritation), sensory (centripetal) nerve fiber(transmits excitation from the receptor to the central nervous system), nerve center(a group of interneurons located at different levels of the central nervous system; transmits nerve impulses from sensory nerve cells to motor ones), motor (centrifugal) nerve fiber(transmits excitation from the central nervous system to the executive organ, the activity of which changes as a result of the reflex).
Simple reflex arc consists of two neurons: sensory and motor (for example, knee reflex), and complex reflex arc- from sensitive, one or more intercalary and motor. Through intercalary neurons, feedback is provided between the working organ and the central nervous system, and the adequacy of the working organ’s response to the received stimulation is monitored. This allows the nerve centers, if necessary, to make changes to the work of the executive bodies.
Along with excitation, inhibition is of great importance for the reflex reaction. In some cases excitation one neuron is not only not transmitted to another, but even inhibits it, that is, causes braking. Inhibition does not allow excitation to spread indefinitely in the nervous system. The relationship between excitation and inhibition ensures the coordinated functioning of all organs and the body as a whole.
There are reflexes unconditional And conditional. To carry out unconditioned (innate) reflexes, the body has ready-made reflex arcs from birth. To implement conditioned (acquired) reflexes, reflex arcs are formed throughout life when the necessary conditions arise for this.

Spinal cord

The spinal cord is located in the bony spinal canal. It looks like a white cord with a diameter of about 1 cm. There are deep longitudinal grooves on the front and back sides. At the very center of the spinal cord is center channel, filled cerebrospinal fluid. The canal is surrounded by gray matter (butterfly-shaped), which in turn is surrounded by white matter. Located in the white matter ascending(axons of spinal cord neurons) and descending paths(axons of brain neurons). The gray matter resembles the outline of a butterfly and consists of anterior, posterior, lateral horns and an intermediate part connecting them. Motor neurons are located in the anterior horns - motor neurons(their axons innervate skeletal muscles), in the posterior - interneurons(connecting sensory and motor neurons), and in the lateral horns - autonomic neurons(their axons go to the periphery to the vegetative nodes).
The spinal cord consists of 31 segments, from each of which a pair of mixed spinal nerves emerge, each having a pair of roots: front(motor neuron axons) and rear(axons of sensory neurons).
Functions of the spinal cord: reflex(implementation of simple reflexes: motor and autonomic - vasomotor, food, respiratory, defecation, urination, sexual) and conductor(conducts nerve impulses to and from the brain). Damage to the spinal cord leads to disruption of conduction functions, resulting in paralysis.

Brain

Brain located in the brain part of the skull. It also has white matter (the pathways between the cerebrum and the spinal cord; between parts of the brain) and gray matter (in the form of nuclei within the white matter; the cortex covering the cerebral hemispheres and the cerebellum). The weight of the adult human brain is about 1400–1600 g.
The brain includes 5 sections: medulla oblongata, hindbrain (pons and cerebellum), midbrain, diencephalon, forebrain (cerebral hemispheres). The human forebrain hemispheres are evolutionarily newer and reach the greatest development (up to 80% of the brain mass). The medulla oblongata, pons (hindbrain), midbrain and intermediate form the brainstem.

Medulla and the bridge are a continuation of the spinal cord and perform reflex (digestion, breathing, cardiac activity, protective reflexes: vomiting, coughing) and conductive functions.
hindbrain consists of the pons and cerebellum. Pons conductive pathways connect the medulla oblongata and cerebellum with large hemispheres. The cerebellum regulates motor acts (balance, coordination of movements, maintaining posture). The midbrain maintains muscle tone and is responsible for orientation, guard and defensive reflexes to visual and auditory stimuli.
Diencephalon regulates complex motor reflexes, coordinates the work of internal organs and carries out humoral regulation (metabolism, water and food consumption, maintaining body temperature). The diencephalon includes the thalamus, epithalamus and hypothalamus. The epiphysis is adjacent to it above, and the pituitary gland below. Thalamus- subcortical center of all types of sensitivity (except smell). In addition, it regulates and coordinates the external manifestation of emotions (facial expressions, gestures, changes in breathing, pulse, pressure). Hypothalamus contains centers of the autonomic nervous system that ensure the constancy of the internal environment, as well as regulate metabolism and body temperature. The hypothalamus is associated with feelings of hunger, thirst and satiety, regulation of sleep and wakefulness. The hypothalamus controls the activity of the pituitary gland. The epithalamus takes part in the work of the olfactory analyzer.
Forebrain(cerebral hemispheres) carries out mental activity (memory, speech, thinking, behavior, etc.). Consists of two large hemispheres: right and left. Gray matter (cortex) is located on top of the hemispheres, white matter is inside. White matter represents the pathways of the hemispheres. Among the white matter are the nuclei of gray matter (subcortical structures).
Cerebral cortex It is a layer of gray matter 2–4 mm thick. Numerous folds, convolutions and grooves increase the area of ​​the cortex (up to 2000–2500 cm2). Each hemisphere is divided by grooves into lobes: frontal(here are the gustatory, olfactory, motor and musculocutaneous zones), parietal(motor and skin-muscular zones), temporal(auditory zone) and occipital(visual area). Each hemisphere is responsible for the opposite side of the body. Functionally, the hemispheres are unequal. The left hemisphere is “analytical”, responsible for abstract thinking, writing and speaking skills. The right hemisphere is “synthetic” and is responsible for imaginative thinking.
Disturbances in brain activity can be caused by hereditary and environmental factors. Damage to individual areas of the brain leads to disruption of various functions.

Autonomic nervous system

Autonomic (autonomic) nervous system controls the activity of internal organs, glands, smooth muscles and is not subject to human will. The autonomic nervous system is divided into sympathetic And parasympathetic. Both of them consist of vegetative nuclei(clusters of neurons lying in the spinal cord or brain), vegetative nodes(clusters of neurons located outside the central nervous system) and nerve endings(in the walls of the working bodies). Thus, the path from the center to the innervated organ consists of two neurons. This is a distinctive feature of the autonomic nervous system from the somatic one, where this pathway is represented by one neuron.

The sympathetic nuclei are located in the spinal cord, the sympathetic nodes near the spine, and the nerve endings in the organs themselves. The parasympathetic nuclei are located in the medulla oblongata, midbrain or end of the spinal cord, and the parasympathetic nodes and nerve endings are in the organs themselves. Nerve fibers extending from the parasympathetic nuclei of the medulla oblongata to the parasympathetic nodes in the organs of the chest and abdominal cavity are called vagus nerves. The mediators at the synapses of the sympathetic nervous system are mainly adrenalin And norepinephrine, parasympathetic - acetylcholine.
Most organs have both sympathetic and parasympathetic innervation. Their effect on organs is opposite. The sympathetic system mobilizes the body’s forces in an extreme situation (increased and intensified heart contractions, blood flow from internal organs to skeletal muscles, weakened juice secretion and stomach movements, weakened intestinal motility), the parasympathetic system is the “lights out” system, promotes the flow of the body’s recovery processes (slowing down and weakening of heart contractions, blood flow to internal organs, increased secretion of juices and stomach movements, increased intestinal motility). This is the function of the autonomic nervous system.

Higher nervous activity

Unconditioned and conditioned reflexes

Higher nervous activity- a set of complex forms of activity of the cerebral cortex and the subcortical formations closest to it, ensuring the most perfect adaptation of animals and humans to the environment.

It is based on the implementation of complex reflex acts.
For the first time, a materialistic explanation of human higher nervous activity was given by I.M. Sechenov. He proved that all acts of conscious and unconscious activity are reflexive. I. P. Pavlov developed the ideas of I. M. Sechenov experimentally. He discovered a nervous mechanism that provides complex forms of response in humans and higher animals to environmental influences - a conditioned reflex. I.P. Pavlov created the doctrine of unconditioned and conditioned reflexes.
Reflex - the body’s response to external or internal influence (irritation), carried out by the central nervous system. The implementation of reflexes is ensured by nerve elements that form reflex arc , that is, the path along which nerve impulses pass from the receptor to the working organ. The reflex arc includes a receptor, an afferent (centripetal) part, a central link (nerve center), an efferent (centrifugal) part, and an executive organ (muscle, gland).
There are different classifications of reflexes. According to their biological significance, reflexes are divided into protective, digestive, sexual, orientation, etc.; according to the modality of the stimulus - visual, auditory, olfactory, etc.; by the nature of the response (depending on the executive organ) - motor, secretory, vascular, etc.
In addition, I.P. Pavlov divided all reflexes into conditioned and unconditioned (table). Unconditioned reflexes - innate reactions of the body. They were formed and consolidated in the process of evolution and are inherited. Conditioned reflexes- acquired reactions of the body. They are developed, consolidated and can fade away throughout life; are not inherited.
Comparative characteristics of unconditioned and conditioned reflexes

Unconditional	Conditional
Congenital, inherited	Acquired by the body during individual development based on “life experience”
Species	Individual
Have constant reflex arcs	They do not have ready-made reflex arcs; they are formed under certain conditions
Relatively constant, little changing	Impermanent, can develop and fade away
Carried out in response to adequate stimulation	They are carried out in response to any irritation perceived by the body; are formed on the basis of unconditioned reflexes
Carried out at the level of the spinal cord and brain stem, subcortical nuclei	Carried out due to the activity of the cerebral cortex with the participation of subcortical structures
Not numerous; cannot ensure the body’s adaptation to constantly changing living conditions	Numerous; some fade away, others arise, ensuring the body’s adaptation to changing conditions

Biological significance of conditioned reflexes. Unconditioned reflexes provide the body with maintaining vital functions in relatively constant conditions of existence. Basic unconditioned reflexes: food(chewing, sucking, swallowing, secretion of saliva, gastric juice, etc.), defensive(pulling a hand away from a hot object, coughing, sneezing, blinking), sexual and etc.
Conditioned reflexes provide the body with a more perfect adaptation to changing conditions of existence. They are developed on the basis of unconditional ones. An example of the formation of a conditioned reflex reaction would be the combination of a sound stimulus (for example, a bell) with feeding an animal. After a number of repetitions of this combination, the animal will experience salivation that occurs at the sound of the bell, even in the absence of food presentation.
Formation and inhibition of conditioned reflexes. The main conditions for the formation of conditioned reflexes include
repeated combination of a previously indifferent (neutral) stimulus (sound, light, tactile, etc.) with the action of a reinforcing unconditioned (or well-developed conditioned) stimulus;
slight precedence in time of the indifferent stimulus in relation to the reinforcing stimulus;
sufficient excitability of the unconditioned reaction (active state of the cerebral cortex);
absence of extraneous irritation or other activity during the development of the reflex.
To ensure adequate behavior, not only the ability to form conditioned reflexes is required, but also the ability to eliminate conditioned reflex reactions, the need for which has ceased. This is ensured by braking processes.
Inhibition of conditioned reflexes can be unconditioned (external and transcendental) and conditioned (internal). External braking occurs if at the moment of action of the conditioned signal an extraneous stimulus begins to act. Extreme braking observed when the intensity of the conditioned signal exceeds a certain limit. In both cases, the conditioned reaction is inhibited. Internal inhibition manifests itself in the extinction of a conditioned reflex over time if it is not reinforced by the action of unconditioned reflexes (that is, if the conditions for its development are not repeated).
There are different classifications of conditioned reflexes. According to their biological significance (according to the type of needs) they distinguish vital conditioned reflexes (defensive, sleep regulation, etc.), zoosocial(parental, territorial, etc.) and conditional self-development reflexes(research, simulation, gaming, etc.). By the nature of reinforcements: conditioned reflexes of the first order(developed on the basis of unconditioned reflexes), conditioned reflexes of the second order(developed on the basis of conditioned reflexes of the first order), etc. By the nature of the conditioned signal: natural(formed in response to natural signs of an unconditioned stimulus, for example, the sight and smell of meat) and artificial(produced in response to signals that are not an indispensable attribute of the stimulus, for example, the clinking of dishes or the words “food is served”).
Thus, the development and inhibition of conditioned reflexes provide a more subtle adaptation of the body to the environment and allow optimizing behavior in response to changes in the external environment.
Features of human higher nervous activity. Conditioned reflex activity is common to both higher animals and humans. Both humans and animals have first signaling system - analysis and synthesis of specific signals, objects and phenomena of the external world. In addition, humans develop second signaling system - speech, writing, abstract thinking. Its emergence is associated with collective work activity and life in society. Words- these are the signals of the primary signals. The second signaling system is socially conditioned - outside of society, without communication with other people, it is not formed. Some animals are capable of making sounds. However, a word for a person is not just a combination of certain sounds, but, first of all, its meaning, the meaning contained in it. With the help of words, people are able to exchange thoughts. Speech and writing allow a person to accumulate and pass on experience from generation to generation. The appearance of speech led to the emergence abstract thinking - thinking using abstract concepts abstracted from specific objects and phenomena.

Psyche, mental phenomena, human behavior

Psyche - a property of highly organized matter, which consists in the subject’s active reflection of the objective world and self-regulation on this basis of his behavior and activities. The psyche manifests itself in three main types of mental phenomena: mental processes, mental states and mental properties. Let's consider some of the psychic phenomena.
Feeling - mental reflection of individual properties of objects of the objective world, arising from their direct impact on the sensory system (sense organs).
Perception - a holistic reflection of objects and phenomena of the objective world based on sensations. Depending on which of the forms of existence of matter is reflected, there are space perception, time perception and motion perception.
Attention - direction of mental activity, concentration on objects and phenomena that are important at the moment. Properties of attention: sustainability(concentrating on one object for a long time), distribution(the ability to maintain attention on several objects simultaneously), volume(maximum number of objects simultaneously captured by attention), concentration(focusing on significant objects and maintaining concentration), switching(intentional transfer of attention from one object to another).
Attention may be involuntary(does not require volitional effort) and arbitrary(requires volitional effort). A person's current behavior is governed by the currently prevailing need. It is called principle of dominance.
Memory - mental reflection of past experience, ensuring its use or exclusion from activity and consciousness. Memory is based on the following processes: remembering, storing, recognizing, reproducing, forgetting. During the course of memory processes, certain changes occur in the nervous system, which persist for some time and affect the nature of the course of reflex reactions.
The forms of manifestation of memory are extremely diverse. Depending on the nature of mental activity that predominates in the activity, memory can be motor or motor (memory of movements - household, sports, labor and other motor skills), figurative(memory of images of surrounding objects, sounds, smells, etc.), emotional(memory of experienced feelings and emotions), verbal-logical(memory of read, heard, spoken words and thoughts). Verbal-logical memory is divided into logical(memorizing cause-and-effect relationships of verbal information) and mechanical(memorizing texts that are difficult to organize logically).
Depending on the purpose of the activity, memory is divided into involuntary(memorization and reproduction occur automatically, without volitional efforts) and arbitrary(there is a goal of memorization, willpower is required).
Depending on the time of storage of information, memory can be short-term(information will either be forgotten or go into long-term memory), long-term(long-term preservation of experience; preservation depends on the frequency of use of the stored information, the total amount of information received by a person before and after this material, etc.) and operational(can be either short-term or long-term; always ready for use).
Memorization happens mechanical(a person is not able to apply such knowledge in life) and meaningful. Memory can be trained. One of the important conditions for memorization is repetition.
Thinking - the process of cognition of the real world based on an indirect and generalized reflection of reality. Thinking allows us to discover the essential aspects of objects and phenomena hidden from direct observation. Depending on the material with which a person operates in mental activity, thinking is divided into visually effective(operating with specific objects), visual-figurative(operating with images of objects) and conceptual, or abstract (operating with abstract concepts).
Feelings - a mental process that reflects a person’s attitude to objects and phenomena, characterized by relative stability. Emotions - a person’s momentary subjective attitude to reality and to himself in a specific situation; external manifestations of feeling. Needs, feelings and emotions play the role of internal regulators of behavior in a person’s life. Senses perform two functions: signaling(imprinting in memory a specific situation and the emotional experiences associated with it) and regulatory(expression of emotion in various changes in the internal environment and in various motor manifestations). Depending on whether a person’s needs are met or not, he will experience positive feelings(for example, joy) or negative(eg grief).
There are usually five main forms of experiencing feelings: feeling tone, emotions, affects, stress, mood. On the basis of simple feelings, the so-called higher feelings are formed. These include moral, intellectual, aesthetic and practical feelings.
Temperament - a stable combination of dynamic features of the psyche (activity, emotionality, etc.), determined by the persistent innate properties of the nervous system. Based on different combinations of indicators characterizing the processes of excitation and inhibition (strength, balance and mobility of nervous processes), I. P. Pavlov identified 4 types of higher nervous activity. This division coincides with the classification of temperaments proposed by Hippocrates more than 2 thousand years ago.
1. Strong balanced mobile type (sanguine) - strong nervous system (high efficiency of nerve cells), balance of excitation and inhibition, high mobility of nervous processes (rapid change of states of the nervous system).
2. Strong balanced inert type (phlegmatic person) - strong nervous system, balance of excitation and inhibition, low mobility of nervous processes.
3. Strong unbalanced mobile type (choleric) - a strong nervous system, a predominance of excitation processes over inhibition, high mobility of nervous processes.
4. Weak unbalanced inert type (melancholic) - weak nervous system (low efficiency of nerve cells), the predominance of inhibition processes over excitation, low mobility of nervous processes.
Human behavior. Normal functioning of the body is possible only by maintaining a relatively constant composition of the internal environment. The need for something necessary for this causes a special state - need. Need - a source of activity, a state that expresses a person’s dependence on the conditions of existence.
There are two levels of needs. First level includes vital, social and ideal needs. Vital needs are associated with the life support of a person as a biological being (needs for oxygen, water, food, warmth, sleep, safety, procreation, saving energy, etc.). Social needs conditioned by a person’s life in society (needs for attention, love, care, belonging to a group, following norms and ideology, self-realization, etc.). Ideal Needs are associated with the emergence of consciousness in a person (the need for truth, faith, knowledge of oneself, the world around us, one’s place in the world, the meaning of life; the need for beauty, justice, etc.). Second level represented by self-valued needs. Self-valued needs - secondary needs, without which the satisfaction of primary needs is difficult or impossible (the need for equipment - a reserve of strength and means, the need to overcome - arises in the process of forming the will and self, etc.).
Motive - an object (material or ideal) that serves to satisfy a need. There are motives conscious(beliefs, aspirations, intentions, dreams, ideals, passions, interests) and unconscious(attractions, emotions, attitudes).
Human behavior - a complex set of motor acts aimed at satisfying the needs of the body. Individual behavior of a person, his character depend to the greatest extent on his social experience(experience of communicating with people and the outside world) and to a lesser extent (for people without congenital malformations) from heredity. The formation of social experience begins at birth. The most persistent character traits (altruist or egoist, sociable or withdrawn, active or passive) are formed by the age of 3–5. Character, behavior, habits can change throughout life, but in childhood the most important traits are laid down that determine behavior in extreme situations, when there is no time left to think.

Consciousness

Consciousness - this is the highest level of reflection of reality, manifested by the individual’s ability to give himself a clear account of his surroundings, the present and past times, make decisions and manage his behavior in accordance with the situation. Consciousness is characterized by the inclusion of oneself in the body of knowledge about the world around us, that is, awareness of one’s existence. Of all living organisms living on Earth, consciousness is inherent only in humans.
Signs of consciousness: 1) attention and ability to concentrate; 2) the ability to evaluate the upcoming action, that is, the ability to expect and predict; 3) the ability to generate abstract thoughts, operate with them, express them in words or in another way; 4) awareness of one’s “I” and recognition of other individuals; 5) the presence of aesthetic values.
There are different states of consciousness. Unconscious state - an extreme state in which only psychovegetative reactions are recorded; manifestations of cognitive and emotional processes are absent. Dream - a state that involves the experience of dreams, allows for subliminal perception and partial memorization of the content of dreams. Wakefulness - a state of awareness of the surrounding world and oneself, accessible to introspection. It includes the entire spectrum of mental manifestations within the framework of awareness - perception, memory, attention, thinking and self-regulation.

Dream

Alternation of sleep and wakefulness is a necessary condition of human life. A person spends about a third of his life sleeping. During wakefulness, the brain is maintained in an active state due to impulses coming from receptors. When the flow of impulses into the brain ceases or is sharply limited, sleep develops.
The following main functions of sleep are distinguished: compensatory-restorative- during sleep, a number of metabolic transformations take place aimed at restoring the body’s expended resources and ensuring trophic processes in tissues; informational- during sleep, processing, analysis and sorting of information received during wakefulness apparently occurs; adaptive - in evolutionary terms, in animals, sleep provides security while maintaining immobility in secluded places.
During sleep, the muscles are relaxed, breathing is rare, skin sensitivity, vision, hearing, smell, metabolism, blood pressure, heart rate, and body temperature are reduced.
During sleep, the brain goes through several different phases, which repeat approximately every hour and a half. Sleep consists of two qualitatively different states - slow-wave sleep and REM sleep. They differ in the types of electrical activity of the brain, heart contractions, breathing, muscle tone, and eye movements.
slow sleep is divided into several stages:
1. Nap. At this stage, the main bioelectrical rhythm of wakefulness, the alpha rhythm, disappears in the electroencephalogram (EEG). It gives way to low-amplitude oscillations. This is the stage of falling asleep. At this stage, a person may experience dream-like hallucinations.
2. Superficial sleep. It is characterized by the appearance of sleep spindles - a spindle-shaped rhythm of 14–18 vibrations per second. When the first spindles of sleep appear, a person’s consciousness turns off. During pauses between such spindles, a person can easily be awakened.
3. Delta sleep. At this stage, high-amplitude slow oscillations - delta waves - appear in the EEG. This is the deepest period of sleep. A person has reduced muscle tone, there is no eye movement, the breathing rhythm and pulse stabilize and become less frequent, and body temperature decreases (by 0.5 °C). It is very difficult to awaken a person from delta sleep. As a rule, a person awakened during this phase of sleep does not remember dreams, he is poorly oriented in his surroundings, and incorrectly estimates time intervals (underestimates the time spent in sleep). Delta sleep is the period of greatest disconnection from the outside world. It predominates in the first half of the night.
REM sleep - This is the last stage in the sleep cycle. At this moment, the EEG rhythms are similar to the rhythms of wakefulness. Cerebral blood flow increases with strong muscle relaxation, with sharp twitching in certain muscle groups. The combination of EEG activity and complete muscle relaxation gave another name to this stage of sleep - paradoxical dream. There are sudden changes in heart rate and breathing (a series of frequent inhalations and exhalations, alternating with pauses), and an episodic rise and fall in blood pressure. Rapid eye movements are observed with closed eyelids. When awakening from this stage of sleep, people report dreaming 80–90% of the time. According to I.M. Sechenov, dreams are unprecedented combinations of experienced impressions.
The structure and duration of sleep changes with age. Newborns sleep 17–18 hours a day, and paradoxical sleep accounts for about half of the total sleep duration. At the age of 4–6 years, the need for sleep is reduced to 10–12 hours per day, and the proportion of the paradoxical phase decreases to 20% of its total duration. This ratio usually persists into adulthood. The required total duration of sleep in adults is usually 7–8 hours. It has been established that if the duration of night sleep is reduced by 1.3–1.5 hours, this will affect the state of wakefulness during the day. Sleeping 6.5 hours for a long time can undermine a person's health. However, the need for sleep duration is very individual. In addition, the structure of sleep changes under the influence of external factors, for example, when learning, adapting to a new environment, etc.

Sense organs

Our body detects various changes occurring in the external environment through the senses: touch, vision, hearing, taste and smell. Each of them has specific receptors that perceive a certain type of irritation.
A person perceives the world around him through his senses (analyzers). As a result of irritation of the sensory organs in the cerebral hemispheres, Feel. It happens through sensations perception And orientation in the environment.
Analyzer (sense organ)- consists of three sections: peripheral, conduction and central. Peripheral (perceiving) The analyzer link is receptors. They transform signals from the outside world (light, sound, temperature, smell, etc.) into nerve impulses. Depending on the method of interaction of the receptor with the stimulus, there are contact(skin, taste receptors) and distant(visual, auditory, olfactory) receptors. Conductor link analyzer - nerve fibers. They conduct excitation from the receptor to the cerebral cortex. Central (processing) link analyzer - a section of the cerebral cortex. A malfunction of one part causes a malfunction of the entire analyzer.
There are visual, auditory, olfactory, gustatory and skin analyzers, as well as a motor analyzer and a vestibular analyzer. Each receptor is adapted to its own specific stimulus and does not perceive others. Receptors are able to adapt to the strength of the stimulus by reducing or increasing sensitivity. This ability is called adaptation.

Visual analyzer

Receptors are excited by light quanta. The organ of vision is the eye. It consists of the eyeball and an auxiliary apparatus. Auxiliary apparatus represented by eyelids, eyelashes, lacrimal glands and muscles of the eyeball. The eyelids are formed by folds of skin lined on the inside with mucous membrane (conjunctiva). Eyelashes protect the eyes from dust particles. Lacrimal glands located in the outer upper corner of the eye and produce tears that wash the front of the eyeball and enter the nasal cavity through the nasolacrimal duct. Muscles of the eyeball set it in motion and orient it towards the object in question.

Eyeball located in the orbit and has a spherical shape. It contains three shells: fibrous (external), vascular (middle) And mesh (inner), as well as the inner core, consisting of lens, vitreous And aqueous humor anterior and posterior chambers of the eye.
The posterior section of the fibrous membrane is a dense opaque connective tissue tunica albuginea ( sclera), front - transparent convex cornea. The choroid is rich in blood vessels and pigments. It actually distinguishes choroid(rear end), ciliary body And iris. The bulk of the ciliary body is the ciliary muscle, which changes the curvature of the lens through its contraction. Iris ( iris) has the appearance of a ring, the color of which depends on the amount and nature of the pigment it contains. There is a hole in the center of the iris - pupil. It can contract and expand due to the contraction of muscles located in the iris.
The retina has two parts: rear- visual, perceiving light stimuli, and front- blind, not containing photosensitive elements. The visual part of the retina contains light-sensitive receptors. There are two types of visual receptors: rods (130 million) and cones (7 million). Sticks are excited by weak twilight light and are unable to distinguish color. Cones are excited by bright light and are able to distinguish color. The rods contain red pigment - rhodopsin, and in cones - iodopsin. Under the influence of light quanta as a result of photochemical reactions, these substances disintegrate and are restored in the dark. In the absence of vitamin A in the body, which restores rhodopsin, the disease develops night blindness- inability to see in low light or darkness. The retina has three types of cones that perceive red, green and blue-violet colors. Recognition of all other colors depends on the combination of the three primary colors. Simultaneous and equal stimulation of three types of cones gives sensations of white color. The cones are concentrated in the center of the retina. Directly opposite the pupil there is yellow spot- the place of best vision, which contains only cones. Therefore, we see objects most clearly when the image falls on the yellow spot. Towards the periphery of the retina, the number of cones decreases, and the number of rods increases. Only sticks are located along the periphery. The place on the retina from which the optic nerve emerges is devoid of receptors and is called blind spot.
Most of the cavity of the eyeball is filled with a transparent gelatinous mass, forming vitreous, which maintains the shape of the eyeball. Lens It is a biconvex lens. Its back part is adjacent to the vitreous body, and its front part is facing the iris. When the muscle of the ciliary body associated with the lens contracts, its curvature changes and light rays are refracted so that the image of the object of vision falls on the macula of the retina. The ability of the lens to change its curvature depending on the distance of objects is called accommodation. If accommodation is disturbed, there may be myopia(the image is focused in front of the retina) and farsightedness(the image is focused behind the retina). With myopia, a person sees distant objects unclearly, and with farsightedness, near objects. With age, the lens hardens, accommodation deteriorates, and farsightedness develops. Aqueous humor is the liquid that fills the anterior and posterior chambers of the eye. The anterior chamber is located between the cornea and the iris, the posterior chamber is located between the iris and the lens.
Receptors are excited by light quanta. Light rays pass through several refractive media (cornea, aqueous humor, lens, vitreous body) and enter the retina, which perceives them. As a result of the refraction of rays on the retina, the image is inverted and reduced. Thanks to the processing in the cortex of information received from the retina and receptors of other senses, we perceive objects in their natural position.
Photochemical reactions in cones and rods cause nerve impulses, which are transmitted through the optic nerve to the visual zone of the cerebral cortex.

Hearing analyzer

The receptors are excited by sound vibrations in the air. The organ of hearing is the ear. It consists of outer, middle and inner ear. The outer ear consists of the pinna and the auditory canal. Ears serve to capture and determine the direction of sound. External auditory canal begins with the external auditory opening and ends blindly, eardrum, which separates the outer ear from the middle ear. It is lined with skin and has glands that secrete earwax.
Middle ear consists of the tympanic cavity, auditory ossicles and auditory (Eustachian) tube. The tympanic cavity is filled with air and connected to the nasopharynx by a narrow passage - auditory tube, through which the same pressure is maintained in the middle ear and the space surrounding the person. Auditory ossicles - malleus, incus and stapes- movably connected to each other. Vibrations from the eardrum are transmitted through them to the inner ear.
Inner ear consists of a bony labyrinth and a membranous labyrinth located in it. Bone labyrinth contains three sections: vestibule, cochlea and semicircular canals. Snail refers to the organ of hearing, the vestibule and semicircular canals - to the organ of balance (vestibular apparatus). The cochlea is a bone canal twisted in the form of a spiral. Its cavity is divided by a thin membranous septum - the main membrane on which receptor cells are located. The vibration of the cochlear fluid irritates the auditory receptors.
The human ear perceives sounds with a frequency from 16 to 20,000 Hz. Sound waves reach the eardrum through the external auditory canal and cause it to vibrate. These vibrations are amplified (almost 50 times) by the ossicular system and transmitted to the fluid in the cochlea, where they are perceived by auditory receptors. The nerve impulse is transmitted from the auditory receptors through the auditory nerve to the auditory zone of the cerebral cortex.

Vestibular analyzer

The vestibular apparatus is located in the inner ear and is represented by the vestibule and semicircular canals. vestibule consists of two bags. Three semicircular canals located in three mutually opposite directions, corresponding to three dimensions of space. Inside the sacs and channels there are receptors that are able to sense fluid pressure. The semicircular canals perceive information about the position of the body in space. The bags perceive deceleration and acceleration, changes in gravity.
Excitation of the receptors of the vestibular apparatus is accompanied by a number of reflex reactions: changes in muscle tone, contraction of muscles that help straighten the body and maintain posture. Impulses from the receptors of the vestibular apparatus travel through the vestibular nerve to the central nervous system. The vestibular analyzer is functionally connected to the cerebellum, which regulates its activity.

Taste analyzer

Taste buds are irritated by chemicals dissolved in water. The organ of perception is taste buds - microscopic formations in the mucous membrane of the oral cavity (on the tongue, soft palate, posterior wall of the pharynx and epiglottis). Receptors specific to the perception of sweet are located at the tip of the tongue, bitter - on the root, sour and salty - on the sides of the tongue. With the help of taste buds, food is tasted, its suitability or unsuitability for the body is determined, and when they are irritated, saliva, gastric and pancreatic juices are released. The nerve impulse is transmitted from the taste buds through the taste nerve to the taste zone of the cerebral cortex.

Olfactory analyzer

Smell receptors are irritated by gaseous chemicals. The sensory organ is the sensory cells in the nasal mucosa. The nerve impulse is transmitted from the olfactory receptors through the olfactory nerve to the olfactory zone of the cerebral cortex.

Skin analyzer

The skin contains receptors that perceive tactile (touch, pressure), temperature (heat and cold) and pain stimuli. The organ of perception is the receiving cells in the mucous membranes and skin. The nerve impulse is transmitted from tactile receptors through the nerves to the cerebral cortex. With the help of tactile receptors, a person gets an idea of ​​the shape, density, and temperature of bodies. There are most tactile receptors on the tips of the fingers, palms, soles of the feet, and tongue.

Motor analyzer

Receptors are excited when muscle fibers contract and relax. The organ of perception is the sensory cells in muscles, ligaments, and on the articular surfaces of bones.

1. Muscle work, fatigue. The importance of physical activity for improving human health. Prevention of flat feet and curvature of the spine

The human muscular system is formed by striated and smooth muscles. Striated muscles are also called skeletal muscles, since they are connected through tendons to the bones of the skeleton (except for facial muscles). Striated muscles make up on average 42% of a person's body weight. These muscles contract voluntarily, developing significant but relatively short efforts. Striated muscles are formed by long (up to 10 cm) multinuclear fibers, which, however, are several times thinner than a human hair. Under a microscope, it can be seen that these fibers have transverse striations, which arise due to the ordered arrangement of fibers of the contractile proteins actin and myosin in them.

Contraction occurs under the influence of impulses coming from the central nervous system. Impulses from a single motor neuron, most often located in the anterior horns of the gray matter of the spinal cord, lead to the contraction of from units to thousands of muscle fibers. During contraction, the actin and myosin filaments move relative to each other - the muscle shortens and thickens. Muscle contraction takes about 0.01 s.

Skeletal muscles are very often joint flexors or extensors. For example, the elbow joint flexes when the biceps muscle contracts, and extends when the triceps muscle contracts. With the simultaneous contraction of these two muscles, the elbow joint is fixed in one position.

A large amount of glucose, other nutrients, oxygen, and ATP are spent on muscle work. These substances are brought to the muscles by blood. The blood removes metabolic products from the muscles: CO2, lactic acid, etc.

If a muscle contracts for a long time, at a fast rhythm or under heavy load, then it develops fatigue. Fatigue is a temporary decrease in muscle performance, which most often occurs when harmful metabolic products accumulate in it and disappears after rest. Another cause of fatigue is inhibition of the motor centers of the brain, which occurs during prolonged work.

Main groups of skeletal muscles and their functions

1. Muscles of the limbs - movement of the limbs, maintaining body position.

2. Muscles of the neck and back - holding and moving the head, ensuring the vertical position of the body, bending the back.

3. Chest muscles - arm movements, breathing.

4. Abdominal muscles – bending forward and to the sides, protecting the abdominal organs.

5. Head muscles – chewing, facial expressions.

In addition to striated muscles, the human body contains smooth muscles that are part of the internal organs: stomach, intestines, arterial vessels, etc. Smooth muscles contract slowly and regardless of desire, although they are also controlled by the nervous system. Their fibers are short and single-core. Smooth muscles can remain in a contracted state for a very long time.

In order for a schoolchild’s body to develop correctly and grow into a healthy, strong person, it is necessary to constantly train the muscular system. Training improves coordination of movements, increases muscle performance, and accelerates muscle recovery when tired. The load on the muscles improves a person’s condition, creates a feeling of cheerfulness, and has a positive effect on the functioning of the nervous and circulatory systems.

The formation of the human skeleton and muscular system occurs during childhood and adolescence. The most common disorders that you can fight on your own are curvature of the spine and flat feet.

To avoid curvature of the spine, you should sit straight at your desk, without tilting your head to your chest. There should be a gap of 3–5 cm between the chest and the edge of the desk or table, the forearms should rest freely on the desk, and the feet should rest on the floor or the footrest of the desk. In lower grades, it is better for schoolchildren to use a backpack rather than a briefcase.

To prevent flat feet, i.e. lowering of the arch of the foot, you should wear shoes with a back, with elastic soles, and low heels.

2. Structure and vital activity of plant and animal cells

The structure and life activity of plant and animal cells have much more in common than differences. Both plant and animal cells eat, breathe, divide, etc. Both plant and animal cells have an outer cell membrane, nucleus, cytoplasm, endoplasmic reticulum, mitochondria, ribosomes, Golgi apparatus, and cellular inclusions. However, there are a number of differences between plant and animal cells that can be presented in table form.

Generalized animal cell (light microscopy). 1 – mitochondria; 2 – cytoplasm; 3 – nutrient granules; 4 – Golgi apparatus; 5 – plasma membrane; 6 – centrioles; 7 - core; 8 – nucleoplasm; 9 – nucleolus; 10 – chromatin; 11 – nuclear membrane; 12 – secretory granules

Generalized plant cell (light microscopy). 1 – chloroplast; 2 – grains; 3 – plasma membrane; 4 - core; 5 – nucleolus; 6 – chromatin; 7 – nucleoplasm; 8 – nuclear membrane; 9 – cell walls of neighboring cells; 10 – plasmodesmata; 11 – cell wall; 12 – middle plate; 13 – Golgi apparatus; 14 – secretory granule; 15 – mitochondria; 16 – tonoplast; 17 – cytoplasm; 18 – vacuole

Ticket number 19

1. Regulation of functions in the human body. Relationship between nervous and humoral regulation

In order for the human body to exist normally, constant, fast and very precise regulation of all functions is necessary.

When a person rests, the work of the heart is inhibited, blood pressure is reduced, breathing is less deep and frequent, muscles are relaxed, but the digestive processes are not inhibited during rest. If a person, for example, takes an exam, then the heart rate accelerates, blood pressure rises, breathing quickens, the consumption of glucose and oxygen by the brain increases, etc.

For the constant regulation of physiological processes in the body, there are two mechanisms: humoral and nervous.

Humoral regulation occurs with the help of special regulatory substances coming from special endocrine glands (and sometimes other tissues) into the blood. With the blood, these regulatory substances are distributed throughout the body and can affect all its organs and systems. Humoral regulation is evolutionarily very ancient, but its disadvantage is the relatively slow development of effects: time is required for the release of regulatory substances into the blood, transport through the bloodstream to target organs and interaction with these organs.

In the process of evolution, another regulatory system arose - the nervous system. Nervous influences are transmitted using electrical signals - nerve impulses. These impulses arise in nerve cells - neurons, from which they reach the target organ along long processes - axons. The axon of each neuron grows into a strictly defined point in the body. Impulses travel along axons at very high speeds - up to 120 m/s. Thus, nervous regulation is highly accurate and fast.

Humoral and nervous modes of regulation are closely related to each other, and all processes in our body are necessarily controlled by both methods. Thus, we can talk about a unified neurohumoral regulation in the human body. The fact is that the nervous system is constantly under the influence of chemicals carried by the blood. In turn, the release of chemicals into the blood is controlled by the nervous system.

One of the parts of the brain - the hypothalamus - contains large groups of neurons that are capable of releasing into the blood a number of protein chemicals that regulate the activity of almost all endocrine glands. Thus, this part of the central nervous system is also the most important organ of humoral regulation.

The interaction of two regulatory systems - humoral and nervous - allows for rapid and reliable adaptation of the body to constantly changing environmental conditions.

2. Cell division and its significance

The ability to divide is the most important feature of cells. Without cell division, the number of single-celled creatures cannot increase, a multicellular organism cannot develop from a fertilized egg, and cells cannot arise to replace those that die in the process of life.

There are several types of cell division: amitosis, mitosis, meiosis.

1. Amitosis, or direct division. In this case, the nucleus divides without visible preliminary changes. Amitosis is quite rare.

2. Mitosis, or indirect division. This is a complex step-by-step process. All preparation for division occurs during interphase: the genetic material is doubled (i.e., chromosomes are doubled, which consist of two identical halves - chromatids, connected together in a special region - the centromere); the number of cell organelles increases; proteins necessary for division are synthesized; energy is stored for fission.

1 – interphase; 2 – prophase; 3 – prometaphase; 4 – metaphase; 5 – anaphase; 6 – telophase;
A– nuclear membrane; b– chromosomes; V– centrioles; G– nucleoli

During the first phase of division - prophase - the chromosomes spiral, the nuclear membrane disintegrates, and a fission spindle is formed.

During metaphase, chromosomes are positioned at the equator of the cell and spindle strands are attached to the centromere of each chromosome.

During anaphase, chromosomes are separated into daughter chromatids, which are carried by spindle filaments to the poles of the cell.

And finally, during telophase, chromosomes unwind, the nuclear membranes of two new nuclei are restored, nucleoli are formed, and the spindle disappears. At the same time, a septum or constriction is formed between two cells - and mitosis ends.

As a result of mitosis, one cell produces two cells with the same diploid set of chromosomes as the mother cell.

3. Meiosis is a method of division by which gametes are formed in animals with a half reduction, i.e. haploid, set of chromosomes; In plants, meiosis occurs during the formation of micro- and megaspores.

Meiosis consists of two successive divisions: during the first, homologous chromosomes, each consisting of two chromatids, diverge to the cell poles, and during the second division, chromatids diverge to the cell poles. Thus, meiosis results in four cells, each containing one (haploid) set of chromosomes.

Ticket number 20

1. Reflex is the basis of nervous regulation. Unconditioned and conditioned reflexes, their role in the life of humans and animals

A reflex can be defined as the body's reaction to an influence (stimulus) carried out under the control of the nervous system. The concept of "reflex" comes from the Latin reflexio– I reflect, i.e. reflex is one or another response of the body (its muscles, internal organs), reflecting the effect of a certain signal on the nervous system.

An example of a reflex is the knee reflex. When the neurologist hits the quadriceps tendon with a hammer, the muscle is slightly but sharply stretched. As a result, the sensitive endings of nerve cells (stretch receptors) located directly in the muscle tissue are excited. The bodies of sensory neurons are located in nodes located along the spinal cord. Along the axon of the sensory neuron, excitation (a signal that the muscle is stretched) reaches the spinal cord (more precisely, its anterior horns; see also question 1 of ticket No. 22), where the bodies of motor neurons are located. The motor neuron that receives the signal is also excited. Along its axon, nerve impulses return to the quadriceps femoris muscle, which contracts. As a result, rapid extension of the knee joint occurs.

This example clearly shows that when a reflex reaction is carried out, excitation spreads along the so-called reflex arc. The arc begins with a sensitive structure - a receptor that perceives irritation. The receptor can be “tuned” to signals coming from the outside world (light, sounds, smells) or from the internal environment of the body (for example, the concentration of oxygen in the blood).

The next stage of the arc’s operation is the transmission of the signal along the nerves to the central nervous system. Here, excitation spreads either directly to the motor neuron (as in the case of the knee reflex), or to intermediate (intercalary) nerve cells, and through them to the motor neuron. The presence of interneurons allows our brain to analyze incoming signals and use them to trigger the most “appropriate” reflexes at the moment, regulate the intensity of reactions, connect individual reflexes in a chain, etc.

Finally, along the axon of the motor neuron, the excitation reaches the executive organ, as a result of which the activity of this organ changes. Based on the type of executive organ, reflexes are divided into motor, which ends in contraction of skeletal muscles, and vegetative, as a result of which the functioning of internal organs (glands, heart, etc.) changes.

Russian physiologists I.M. Sechenov and I.P. Pavlov divided all reflexes observed in the behavior of animals and humans into two groups. The first group is innate responses that are inherited from parents and persist throughout life. Such reflexes are species specific, i.e. characteristic of all representatives of this species. The range of stimuli that trigger them is genetically strictly determined (food, pain, the smell of an individual of the opposite sex, etc.). I.P. Pavlov called such reflexes unconditioned, and the stimuli that triggered them were called reinforcers.

The second group of reflexes are acquired responses that are formed as a result of the repeated combination of any indifferent (initially insignificant) stimulus with reinforcement. Such reflexes are individual; they are produced under certain conditions in each individual, can disappear during life or be replaced by other similar reflexes and are not transmitted to offspring. I.P. Pavlov called such reflexes conditioned.

Innate forms of behavior (unconditioned reflexes) were developed in the process of evolution and are the same result of natural selection as the morphological, physiological and other characteristics of the organism. They are genetically strictly defined, therefore, in taxonomy, one of the criteria for a species is behavioral. Unconditioned reflexes are very diverse. They can be classified as follows.

1. Reflexes aimed at preserving the internal environment of the body. These are food, drinking, as well as homeostatic reflexes (maintaining a constant body temperature, optimal breathing and heart rates, etc.).

2. Reflexes that arise when the conditions of the body’s external environment change. These are situational reflexes (flock behavior, nest building, exploratory and imitative reflexes) and defensive reactions.

3. Reflexes associated with the preservation of the species - sexual and parental.

Let us now consider what happens in the nervous system during the development of a conditioned reflex, for example, the reaction of salivation in a dog when a sound is turned on. This reaction is formed on the basis of an unconditioned reflex that develops when food comes into contact with the receptors of the tongue. In this case, the excitation enters the medulla oblongata (where the centers of taste and salivation are located) and from it to the salivary glands. However, each unconditioned reflex has a so-called cortical representation. This is a site in the cerebral cortex, which, if necessary, corrects the work of the subcortical center. When a sound is presented, the auditory center is excited in the temporal cortex. If you give food to a dog at the same time as a sound, then after several combinations a connection is formed between this center and the cortical representation of the unconditioned reflex.

It is this connection (I.P. Pavlov called it a temporary connection) that underlies the conditioned reflex. Subsequently, even if only a sound is presented, the dog will begin to salivate, since the excitation from the auditory center will spread first to the cortical representation of the unconditioned reflex, and from there to the centers of the medulla oblongata.

The formation of conditioned reflexes is the basic principle by which information is processed, accumulated and used in the brain. It has been proven that a conditioned reflex can be formed on the basis of any unconditioned reflex. The stimuli that trigger the reflex (conditioned stimuli) can also be any signals perceived by the senses.

The more complex the nervous system, the greater the contribution conditioned reflexes make to the behavior of the organism. Highly developed animals (mammals) at birth have only unconditioned reflexes, but as they grow up and learn, they acquire many conditioned reflexes, adapting their reactions to specific living conditions. This ability reaches its maximum development in a person who, along with conditioned reflexes to real signals (according to I.P. Pavlov - the first signal system), is capable of forming a huge number of conditioned reflexes to speech stimuli (the second signal system). Gradually becoming more complex, the system of conditioned reflexes covers all aspects of life that are significant for a person and serves as the basis for the emergence and development of the thinking process.

2. Fabrics. The relationship between their structure and functions

The tissue of a multicellular organism is the collection of its cells, united by similarities in structure, function and origin. Following this definition, plants have five main types of tissues: educational, integumentary, mechanical, conductive, basic; in animals there are four types: epithelial, connective, muscular, and nervous.

During evolution, tissues arise as a result of the specialization of initially similar cells to perform a particular task (protection from environmental influences, giving the body mechanical strength, movement). Tissues are structural units from which the organs and organ systems of the entire organism are “assembled”.

Three-dimensional image of the structure of a section of wood of a dicotyledonous plant.
A– cross section; B– tangential cut; IN– radial cut
1 – medullary rays; 2 – wood parenchyma; 3 – vessels;
4 – fibers; 5 – position of the enlarged area in the shoot

The educational tissue of plants consists of small, living, constantly dividing cells. In this case, some of them subsequently undergo growth and can turn into a cell of any other type of plant tissue - i.e. form them. The educational tissue is located at the so-called growth points of the plant - at the tops of the stems and roots. The embryo of the seed also consists of it. In perennial plants, a special type of educational tissue can form - cambium, due to which thickening and formation of annual rings occur.

The integumentary tissues of plants are located at the border with the external environment and perform a protective function. In this regard, they consist of tightly closed cells and can be either single-layered (epidermis) or multilayered (cork). The epidermis contains living cells and covers the leaves and young stems. The epidermis has stomata that regulate the processes of water evaporation and gas exchange. The cork consists of several layers of cells, the cytoplasm of which dies due to a sharp thickening of the cell walls (suberization). Cork performs a protective function even more effectively than the epidermis and is found in its most developed form in perennial plants.

The mechanical (supporting) tissues of plants provide their strength and, if necessary, rigidity. They consist of fiber cells, often dead, with a thick cell wall. This wall (and therefore the entire fiber) can consist predominantly of cellulose and remain flexible, or when impregnated with certain substances it can become more fragile, but much more rigid. The second situation is most typical for wood of perennial plants.

Conductive plant tissues are divided into those that transport water and mineral salts from roots to shoots, and those that conduct nutrients (glucose solution) from leaves to other organs. In flowering plants, these are vessels (xylem) and sieve tubes (phloem), respectively. Both of them consist of elongated cylindrical cells, “planted” with their ends on top of each other. In the vessels, the transverse partitions between the cells disappear; in the sieve tubes, numerous holes appear in the transverse partitions, which actually cause an association with a sieve. Xylem cells are dead, and water is transported through them due to physicochemical processes. The cells of the sieve tubes are alive, although they lack nuclei. Their viability is ensured by nearby companion cells, which are also part of the phloem. Inside stems and roots, xylem occupies a more central position in relation to the phloem, and in leaf veins it is located above it.

The main tissues of plants contain living cells that carry out photosynthesis (primarily in the leaves) or store nutrients (for example, the core of the stem). It is from cells of this type that the bodies (thallus) of lower plants - algae - are composed.

Epithelial (integumentary) tissues of animals, unlike plants, cover the outside of the body and line the cavities inside it. Consequently, their function is not only to protect from external influences, but also to divide the internal environment of the body into a number of isolated compartments. Single-layer epithelia are very diverse in structure and line blood vessels, glandular ducts, the walls of the gastrointestinal tract (including absorptive cells with microvilli), and the walls of the respiratory tract (the cells have cilia). Stratified epithelium forms the outer layer of the skin - the epidermis. The lower cells of the epidermis are constantly dividing, the upper ones perform their own protective function, as a result of which they quickly die and desquamate. Epithelial cells also form glands (pancreas, sweat glands, etc.).

Animal connective tissues are characterized by the presence of a large amount of intercellular substance. It is the properties of this substance that determine the specific function of a particular connective tissue. In the case of the most “liquid” intercellular substance, we are dealing with blood or lymph - tissues that primarily perform transport and protective functions.

If the intercellular substance contains molecules of the building protein collagen, we speak of fibrous connective tissue of greater or lesser density. It forms subcutaneous fatty tissue, membranes and tendons of muscles, and is part of the walls of internal organs. The presence of a very large amount of protein in the intercellular substance leads to the formation of cartilage, and its additional impregnation with calcium phosphate leads to the formation of bone tissue. In these cases, connective tissue ensures the functioning of the musculoskeletal system.

Muscle tissue consists of elongated fiber cells and performs the functions of excitability and contractility inherent only in animal tissues. At the same time, specialized protein molecules located in their cytoplasm ensure the shortening of cells under the influence of certain external influences (most often - signals from the nervous system). Smooth (uniformly colored) and striated muscle fibers are distinguished. The former are formed by mononuclear cells, are part of the walls of internal organs (stomach, intestines, bladder, vessels, ducts) and are capable of prolonged, but relatively weak contractions. The latter are multinucleated, form skeletal muscles, as well as the heart, and are capable of shorter-term, but more powerful contractions. Cardiac muscle tissue is characterized by the presence of special tight junctions between the fibers, due to which excitation is quickly transmitted from cell to cell. This, in turn, ensures simultaneous contraction of large areas of the heart muscle.

Nervous tissue is formed by nerve cells (neurons) and neuroglia. Neurons have special properties - excitability and conductivity, which ensures the fastest transmission of information in our body, as well as its processing and storage. A neuron usually consists of a body and two types of processes: several shorter dendrites branching at an acute angle and a single longer axon. Dendrites perceive information, it is processed in the body, and the axon transmits signals to other cells. Consequently, inside the neuron, information flows in a strictly defined direction - from the dendrites to the body and further to the axon and along the axon. Information is carried out in the form of short electrical impulses.

Individual neurons form chains and networks in nervous tissue. The places of contact between neurons that exist in such circuits are called synapses. At the synapse, a signal is transmitted from neuron to neuron (or muscle fiber, gland cell). Neuroglia are auxiliary cells of nervous tissue that provide optimal conditions for the functioning of neurons. They regulate the composition of the intercellular environment, transfer nutrients from blood vessels, provide mechanical protection and electrical insulation of processes.

Schematic representation of synapses with chemical ( A),
electric ( B) and mixed ( IN) transmission mechanisms.
joint venture– synaptic vesicles; m– mitochondria;
1 – presynaptic membrane; 2 – synaptic cleft;
3 – postsynaptic membrane

In general, we can say that consideration of the characteristics of all these tissues is an excellent example of how the solution of various evolutionary problems by living organisms causes changes at the structural-anatomical level and the level of implementation of various functions (the latter is the area of ​​interest of a special science - physiology).

Ticket number 21

1. Structure and functions of the human nervous system

The nervous system perceives external and internal stimuli, analyzes and stores the information received and, in accordance with it, regulates the functioning of all body systems and ensures coordination of their activities.

The nervous system performs its functions due to the fact that nerve cells (neurons) have a special property - excitability. In response to irritation, nerve cells are capable of generating short electrical signals - nerve impulses: the nerve cell changes its potential from negative to positive in relation to the external environment, and then returns to the resting potential level. This phenomenon is called an action potential and is a universal form of neuronal response to a wide variety of stimuli.

After the generation of an action potential in any place of the neuron (usually its dendrite or body), the nerve impulse begins to spread throughout its entire membrane and, under certain conditions, is eventually sent along the axon to the next nerve cell (muscle fiber, etc.). This ability to transmit a signal along its processes to other cells is called conductivity and is the second main property of neurons that ensures the functioning of the nervous system. The speed of conduction is the most important characteristic that determines the speed of our thinking and response to external events. It reaches 100–130 m/s due to the presence of special electrically insulating sheaths around the axons, formed by neuroglial cells. Such membranes are rich in the fat-like substance myelin and are therefore called myelin.

Nerve impulses in sensory neurons arise under the influence of various external stimuli, and in other neurons - under the influence of signals arriving through synapses - the points of contact between neurons.

At the synapse, the axon of the previous nerve cell comes very close to the dendrite (less often, the body) of the next neuron and forms a characteristic thickening - the presynaptic ending. When an action potential arrives at the presynaptic terminal, a special chemical substance is released - a transmitter. The mediator acts on the membrane of the next neuron, causing its excitation and generation of a new nerve impulse or inhibition and cessation of such generation. In this regard, excitatory and inhibitory mediators are released (for example, glutamic acid and gamma-aminobutyric acid, respectively). Connections between nerve cells and peripheral organs are provided by mediators such as acetylcholine and norepinephrine.

So, the conduction of nerve impulses and the release of various mediators can cause the development of two main processes in the nervous system - excitation and inhibition. Excitement is characterized by the conduct and processing of information, its memorization, and the triggering of body responses - reflexes. Inhibition, on the contrary, is blocking the transmission of information and the launch of certain reflexes. Inhibition underlies the adaptation of the nervous system to repeated insignificant signals. It is also a necessary component of attention - when, out of the many stimuli acting on the body, we focus only on the important, significant ones and do not react to the rest.

A striking example of the relationship between the processes of excitation and inhibition in the nervous system is the cyclic change of sleep and wakefulness. This process is ensured by special centers of wakefulness and sleep. The first are associated with various sense organs and wake us up when strong external signals appear (for example, an alarm clock ringing), and then maintain the tone of the nervous system during the daylight hours. The latter are capable of inhibiting the centers of wakefulness and the work of most nerve centers to ensure their rest. However, even during sleep, the nervous system periodically enters a more active state. This is the so-called rapid or paradoxical sleep, associated with the processing of information accumulated during the day and dreams.

Anatomically, the nervous system is divided into central and peripheral. In humans, the central nervous system includes the spinal cord and the brain. The cell bodies of neurons are mainly found here, their clusters forming the gray matter of the brain. Clusters of nerve cell processes covered with myelin sheaths are called the white matter of the brain. The peripheral nervous system is the nerves and ganglia (clusters of gray matter outside the central nervous system). The nervous system is formed by three types of neurons with different functions: sensitive cells that transmit nerve impulses to the brain from the organs of vision, hearing, etc., as well as from internal organs; executive cells that conduct action potentials to muscles and glands; intercalary (intermediate) cells. There are most of the latter in the human brain, and they provide the ability of the nervous system to respond subtly to changes in external conditions, learning and the formation of temporary connections of both the first and second signaling systems.

2. Agricultural plants. Their origin and cultivation

Agricultural (cultivated) plants originated from wild species. Primitive man, finding plants with edible fruits, seeds, and roots, later began to grow them near his home. At the same time, he noticed that caring for plants (loosening the soil, watering, destroying weeds and pests) increases and improves the yield. In addition, individuals with the most valuable properties were constantly selected, since they were the highest quality seed material. As a result, spontaneous selection of cultivated plants occurred and various varieties appeared.

A variety is a homogeneous group (population) of plants with certain characteristics and properties, artificially created by man. The characteristics of the variety are inherited, although they are fully manifested only under certain climatic conditions and appropriate care (agricultural technology). It is characteristic that in field and vegetable growing the vast majority of plants are propagated by seeds, and purely genetic factors are sufficient to preserve the properties of the variety. Vegetative propagation (cuttings, grafting, etc.) is usually used in fruit growing.

Currently, breeding is one of the applied areas of biology and uses not only traditional methods of crossing and selection, but also various genetic and molecular biological methods to create and improve plant varieties. They make it possible to create polyploid varieties, carry out distant (interspecific) hybridization, and also carry out targeted changes in plant DNA, giving them resistance to various diseases, etc.

The more diverse the source material used for breeding, the more opportunities it provides for the successful creation of new varieties and the more effective the selection. The source of such diversity is primarily the original (wild) populations of plants - the ancestors of modern wheat, potatoes, etc. Moreover, the area where the greatest genetic diversity of the ancestors of any type of cultivated plant was found is, obviously, the place of its origin and domestication. A systematic study of such areas was carried out by N.I. Vavilov, who established the following 8 centers of ancient agriculture.

1. The Indian (South Asian) center includes the Hindustan Peninsula, South China, and Southeast Asia. This center is the birthplace of rice, citrus fruits, cucumbers, sugar cane and many other types of cultivated plants.

2. The Chinese (East Asian) center includes Central and Eastern China, Korea, and Japan. In this center, millet, soybeans, buckwheat, radishes, cherries, and plums were cultivated by man.

3. The Central Asian center includes the countries of Central Asia, Iran, Afghanistan, and North-West India. This is the birthplace of soft varieties of wheat, peas, beans, flax, garlic, carrots, pears, and apricots.

4. The Western Asian center includes Turkey and the countries of Transcaucasia. Rye, barley, roses, and figs were cultivated in this area.

5. The Mediterranean center includes European, African and Asian countries located along the shores of the Mediterranean Sea. This center is the birthplace of cabbage, olives, parsley, and sugar beets.

6. The Abyssinian center is located in a relatively small area of ​​modern Ethiopia and on the southern coast of the Arabian Peninsula. This center is the birthplace of durum wheat, sorghum, bananas; Of all the centers of ancient agriculture, it is the most ancient.

7. The Central American center includes Mexico, the Caribbean islands and parts of Central America. These places are the birthplace of corn, pumpkin, cotton, tobacco, and red pepper.

8. The South American Center includes the western coast of South America. This is the birthplace of potatoes, pineapple, tomatoes, and beans.

N.I. Vavilov concluded that, firstly, similar but different plant species were domesticated independently in different areas. For example, legumes began to be grown in Central Asia (peas, beans) and South America (beans). Secondly, ancient farmers selected only 1-2 of the many wild species for breeding. If you look at the map, you can see that the centers of origin of cultivated plants coincide with the locations of the great civilizations of antiquity (Egypt, China, the Mayan states, Aztecs, etc.).

Analysis of a huge number of cultivated plants and their wild ancestors allowed N.I. Vavilov to formulate the law of homological series of hereditary variability, which is of great importance both for genetics and for practical selection: “Genetically similar genera and species are characterized by similar series of hereditary variability, and knowing a number of forms within one species, one can predict the presence of similar forms in related species and childbirth."

So, N.I. Vavilov studied the variability of traits in plants from the cereal family. Of the 38 different characters that are characteristic of various species of this family (color of glumes and grains, awned and awnless, grain shape, leaf structure, seedling color, winter and springiness, cold resistance, etc.), rye and wheat have N. AND. Vavilov discovered 37 traits each, 35 in oats and barley, 32 in corn and rice.

The law of homologous series makes it possible to predict the existence of wild plants with traits valuable for breeding work. For example, for a long time only multi-seeded varieties of sugar beets were known, in which 3–5 seeds are connected into a ball. During its germination, excess shoots had to be removed manually. However, it turned out that wild beet species have plants with single-seeded fruits. Then the search began for fruits with one seed and in cultivated beets. As a result of examining a huge number of plants, it was possible to find such individuals, and on their basis the current varieties of sugar beets with one seed were obtained.

The process of growing cultivated plants includes a number of stages, the correct implementation of which allows you to obtain the highest possible yield. The seeds selected for planting should be properly stored in a dry and usually cool place. Before planting, it is recommended to subject them to chemical treatment that kills spores of pathogenic organisms. In early spring, seeds of cold-resistant plants (wheat, oats, peas) are sown, which germinate at low temperatures and plenty of moisture. When the soil warms up enough, seeds of heat-loving plants (corn, beans, cucumbers, tomatoes) are sown. The depth of sowing seeds depends on their size and soil properties.

During the development of seedlings, timely watering, loosening the soil to provide oxygen to the roots, and applying mineral fertilizers are very important. Plants are periodically treated with chemicals that kill pests. Picking roots, hilling and tying up plants, removing excess shoots and ovaries - all this is aimed at forming a developed root system and creating optimal conditions for fruit ripening. In gardening, proper pruning and formation of the tree crown are of particular importance.

Among cultivated plants, various types and varieties of cereals are of utmost importance for human life. The endosperm of their seeds contains significant amounts of both carbohydrates and proteins, which makes flour and cereals the most important food products. Legumes are even richer in proteins. In addition, their cultivation enriches the soil with nitrogen. The source of the most beneficial fats for our body are oilseeds. Vegetables and fruits supply dietary carbohydrates, fiber necessary for normal intestinal function, and many minerals and vitamins.

Thus, plant products form the basis of our nutrition (and the nutrition of domestic animals), and therefore the task of selection and cultivation of cultivated plants remains and will remain of great importance for humanity.

Ticket number 22

1. Central nervous system. Structure and functions of the spinal cord and parts of the brain

The central nervous system includes the spinal cord and brain, which develop from the neural tube in all vertebrates. The average weight of the spinal cord is about 300 g, the brain - about 1.5 kg. The spinal cord is located in the spinal canal and is divided longitudinally into 31 similarly organized segments. A cross-section shows that in the center of the spinal cord are the cell bodies of neurons that form the gray matter. Around the gray matter are the processes of the nerve cells of the spinal cord itself, as well as the axons of the neurons of the brain and peripheral nerve ganglia coming into the spinal cord, which form the white matter.

1 – central groove; 2 – medullary vault; 3 – large brain; 4 – corpus callosum; 5 – thalamus; 6 – frontal lobe; 7 – hypothalamus; 8 – optic chiasm; 9 – pituitary gland; 10 – midbrain; 11 – pons; 12 – medulla oblongata; 13 – spinal cord; 14 – fourth ventricle of the brain; 15 – cerebellum; 16 – cerebral aqueduct; 17 – occipital lobe; 18 – pineal body; 19 – parieto-occipital sulcus; 20 – parietal lobe

In cross section, the gray matter is butterfly-shaped and has anterior, posterior, and lateral horns. The anterior horns contain motor neurons, along whose axons excitation reaches the muscles of the limbs and trunk. The dorsal horns contain the bodies of interneurons that connect the processes of sensory cells with the bodies of motor neurons, as well as receiving signals from the brain. The cell bodies of neurons of the autonomic nervous system are located in the lateral horns. A pair of spinal nerves (31 pairs in total) arise from each segment of the spinal cord, and each segment of the spinal cord is responsible for a specific area of ​​the human body.

The spinal cord performs two main functions: conductive and reflex. The first of them is that information from skin and muscle receptors “rises” through the fibers of the white matter into the brain; in turn, motor commands are sent from the centers of the brain to the spinal cord. The reflex function of the spinal cord is ensured by the fact that its neurons control the movements of skeletal muscles. In addition, the vegetative centers located here regulate the activity of the cardiovascular, respiratory, digestive and other systems, triggering various vegetative reflexes. An example of the simplest spinal cord reflex is the knee reflex described in ticket No. 20.1.

The brain is divided into five sections: the medulla oblongata, the hindbrain (which includes the pons and cerebellum), the midbrain, the diencephalon and the cerebral hemispheres. The medulla oblongata serves as a natural continuation of the spinal cord and is the oldest thickening of the anterior end of the neural tube. In this regard, the centers of many of the most important reflexes for life lie in it. Thus, the medulla oblongata contains the respiratory and vasomotor centers. The latter, constantly generating nerve impulses, maintains optimal lumen of arterial vessels (the tone of their walls). The medulla oblongata region is the site of entry and exit of most cranial nerves that perform various sensory, motor and autonomic functions. In the central part of the medulla oblongata, the reticular formation begins - a zone containing the main centers of sleep and wakefulness.

The pons is an anatomical and functional continuation of the medulla oblongata. Some cranial nerves are also connected to it. The pons plays an important role in switching motor signals from the cerebral cortex to the cerebellum, which is located behind the medulla oblongata and the pons, under the occipital lobes of the cerebral hemispheres. The cerebellum consists of the vermis (central part) and the hemispheres and is covered on the outside with gray matter, which has a layered structure - the cortex. The cerebellum receives information from the vestibular system, the muscle sensitivity system and various motor centers (including the cerebral hemispheres). Using it, the cerebellum regulates both relatively simple motor functions (maintaining muscle tone and balance; movements associated with movements in space - walking, running, etc.), and motor learning, when movement from voluntary, controlled by the cerebral hemispheres, with repeated repetitions it becomes “automatic”, performed without or almost without the participation of consciousness.

The upper part of the midbrain consists of four small tubercles - the quadrigeminal. These are visual and auditory centers that react to the appearance of new signals and control the movements of the eyes and head so as to best view (hear) the object that attracted attention (the so-called orienting reflex). Under the quadrigeminal region there is an area that is the main sleep center of our brain. Even lower are clusters of neurons that perform motor functions (flexion of limbs, regulation of the level of motor activity).

To be continued