Nervous regulation of the body's activities is carried out with help. Nervous and humoral regulation of activity
Description of the presentation by individual slides:
1 slide
Slide description:
2 slide
Slide description:
REGULATION – from lat. Regulo - direct, organize) a coordinating influence on cells, tissues and organs, bringing their activities into line with the needs of the body and changes in the environment. How does regulation occur in the body?
3 slide
Slide description:
4 slide
Slide description:
The nervous and humoral ways of regulating functions are closely related. The activity of the nervous system is constantly influenced by chemicals carried through the bloodstream, and the formation of most chemicals and their release into the blood is under constant control of the nervous system. The regulation of physiological functions in the body cannot be carried out using only nervous or only humoral regulation - this is a single complex of neurohumoral regulation of functions.
5 slide
Slide description:
Nervous regulation is the coordinating influence of the nervous system on cells, tissues and organs, one of the main mechanisms of self-regulation of the functions of the whole organism. Nervous regulation is carried out using nerve impulses. Nervous regulation is fast and local, which is especially important when regulating movements, and affects all(!) systems of the body.
6 slide
Slide description:
The basis of nervous regulation is the reflex principle. A reflex is a universal form of interaction between the body and the environment; it is the body’s response to irritation, which is carried out through the central nervous system and is controlled by it.
7 slide
Slide description:
The structural and functional basis of the reflex is the reflex arc - a sequentially connected chain of nerve cells that ensures the response to stimulation. All reflexes are carried out thanks to the activity of the central nervous system - the brain and spinal cord.
8 slide
Slide description:
Humoral regulation Humoral regulation is the coordination of physiological and biochemical processes carried out through the body's fluids (blood, lymph, tissue fluid) with the help of biologically active substances (hormones) secreted by cells, organs and tissues during their vital activity.
Slide 9
Slide description:
Humoral regulation arose in the process of evolution earlier than nervous regulation. It became more complex in the process of evolution, as a result of which the endocrine system (endocrine glands) arose. Humoral regulation is subordinate to nervous regulation and together with it constitutes a unified system of neurohumoral regulation of body functions, which plays an important role in maintaining the relative constancy of the composition and properties of the body’s internal environment (homeostasis) and its adaptation to changing conditions of existence.
10 slide
Slide description:
Immune regulation Immunity is a physiological function that ensures the body's resistance to the action of foreign antigens. Human immunity makes him immune to many bacteria, viruses, fungi, worms, protozoa, various animal poisons, and protects the body from cancer cells. The task of the immune system is to recognize and destroy all foreign structures. The immune system is a regulator of homeostasis. This function is carried out through the production of autoantibodies, which, for example, can bind excess hormones.
11 slide
Slide description:
The immunological reaction, on the one hand, is an integral part of the humoral one, since most physiological and biochemical processes are carried out with the direct participation of humoral intermediaries. However, often the immunological reaction is targeted in nature and thereby resembles nervous regulation. The intensity of the immune response, in turn, is regulated in a neurophilic manner. The functioning of the immune system is adjusted by the brain and through the endocrine system. Such nervous and humoral regulation is carried out with the help of neurotransmitters, neuropeptides and hormones. Promediators and neuropeptides reach the organs of the immune system along the axons of the nerves, and hormones are secreted by the endocrine glands unrelatedly into the blood and are thus delivered to the organs of the immune system. Phagocyte (immune cell), destroys bacterial cells
STRUCTURE, FUNCTIONS
A person has to constantly regulate physiological processes in accordance with his own needs and changes in the environment. To carry out constant regulation of physiological processes, two mechanisms are used: humoral and nervous.
The model of neurohumoral control is built on the principle of a two-layer neural network. The role of formal neurons of the first layer in our model is played by receptors. The second layer consists of one formal neuron - the cardiac center. Its input signals are the output signals of the receptors. The output value of the neurohumoral factor is transmitted along a single axon of the formal neuron of the second layer.
The nervous, or rather the neurohumoral control system of the human body is the most mobile and responds to the influence of the external environment within a fraction of a second. The nervous system is a network of living fibers interconnected with each other and with other types of cells, for example, sensory receptors (receptors for the organs of smell, touch, vision, etc.), muscle cells, secretory cells, etc. Between all these cells there is no direct connection, since they are always separated by small spatial gaps called synaptic clefts. Cells, both nerve cells and others, communicate with each other by transmitting a signal from one cell to another. If the signal is transmitted throughout the cell itself due to the difference in the concentrations of sodium and potassium ions, then the signal is transmitted between cells by the release of an organic substance into the synaptic cleft, which comes into contact with the receptors of the receiving cell located on the other side of the synaptic cleft. In order to release a substance into the synaptic cleft, the nerve cell forms a vesicle (a shell of glycoproteins) containing 2000-4000 molecules of organic matter (for example, acetylcholine, adrenaline, norepinephrine, dopamine, serotonin, gamma-aminobutyric acid, glycine and glutamate, etc. ). A glycoprotein complex is also used as receptors for a particular organic substance in the cell receiving the signal.
Humoral regulation is carried out with the help of chemicals that enter the blood from various organs and tissues of the body and are carried throughout the body. Humoral regulation is an ancient form of interaction between cells and organs.
Nervous regulation of physiological processes involves the interaction of body organs with the help of the nervous system. Nervous and humoral regulation of body functions are mutually interconnected and form a single mechanism of neurohumoral regulation of body functions.
The nervous system plays a critical role in regulating body functions. It ensures the coordinated functioning of cells, tissues, organs and their systems. The body functions as a single whole. Thanks to the nervous system, the body communicates with the external environment. The activity of the nervous system underlies feelings, learning, memory, speech and thinking - mental processes through which a person not only understands the environment, but can also actively change it.
The nervous system is divided into two parts: central and peripheral. The central nervous system includes the brain and spinal cord, formed by nervous tissue. The structural unit of nervous tissue is a nerve cell - a neuron. - A neuron consists of a body and processes. The body of a neuron can be of various shapes. A neuron has a nucleus, short, thick processes (dendrites) that branch strongly near the body, and a long axon process (up to 1.5 m). Axons form nerve fibers.
The cell bodies of neurons form the gray matter of the brain and spinal cord, and the clusters of their processes form the white matter.
Nerve cell bodies outside the central nervous system form nerve ganglia. Nerve ganglia and nerves (clusters of long processes of nerve cells covered with a sheath) form the peripheral nervous system.
The spinal cord is located in the bony spinal canal.
This is a long white cord with a diameter of about 1 cm. In the center of the spinal cord there is a narrow spinal canal filled with cerebrospinal fluid. There are two deep longitudinal grooves on the anterior and posterior surfaces of the spinal cord. They divide it into right and left halves. The central part of the spinal cord is formed by gray matter, which consists of interneurons and motor neurons. Surrounding the gray matter is white matter, formed by long processes of neurons. They run up or down along the spinal cord, forming ascending and descending pathways. 31 pairs of mixed spinal nerves depart from the spinal cord, each of which begins with two roots: anterior and posterior. The dorsal roots are the axons of sensory neurons. Clusters of cell bodies of these neurons form the spinal ganglia. The anterior roots are the axons of motor neurons. The spinal cord performs 2 main functions: reflex and conduction.
The reflex function of the spinal cord provides movement. Reflex arcs pass through the spinal cord, which are associated with contraction of the skeletal muscles of the body. The white matter of the spinal cord ensures communication and coordinated work of all parts of the central nervous system, performing a conductive function. The brain regulates the functioning of the spinal cord.
The brain is located in the cranial cavity. It includes the following sections: medulla oblongata, pons, cerebellum, midbrain, diencephalon and cerebral hemispheres. White matter forms the pathways of the brain. They connect the brain with the spinal cord and parts of the brain with each other.
Thanks to the pathways, the entire central nervous system functions as a single whole. Gray matter in the form of nuclei is located inside the white matter, forms the cortex, covering the cerebral hemispheres and cerebellum.
The medulla oblongata and the pons are a continuation of the spinal cord and perform reflex and conduction functions. The nuclei of the medulla oblongata and pons regulate digestion, respiration, and cardiac activity. These sections regulate chewing, swallowing, sucking, and protective reflexes: vomiting, sneezing, coughing.
The cerebellum is located above the medulla oblongata. Its surface is formed by gray matter - the cortex, under which there are nuclei in the white matter. The cerebellum is connected to many parts of the central nervous system. The cerebellum regulates motor acts. When the normal activity of the cerebellum is disrupted, people lose the ability to make precise coordinated movements and maintain body balance.
In the midbrain there are nuclei that send nerve impulses to the skeletal muscles, maintaining their tension - tone. In the midbrain there are reflex arcs of orienting reflexes to visual and sound stimuli. The medulla oblongata, pons, and midbrain form the brainstem. 12 pairs of cranial nerves depart from it. Nerves connect the brain with the sensory organs, muscles and glands located on the head. One pair of nerves - the vagus nerve - connects the brain with internal organs: heart, lungs, stomach, intestines, etc. Through the diencephalon, impulses arrive to the cerebral cortex from all receptors (visual, auditory, skin, taste).
Walking, running, swimming are associated with the diencephalon. Its nuclei coordinate the work of various internal organs. The diencephalon regulates metabolism, food and water consumption, and maintaining a constant body temperature.
The part of the peripheral nervous system that regulates the functioning of skeletal muscles is called the somatic (Greek, “soma” - body) nervous system. The part of the nervous system that regulates the activity of internal organs (heart, stomach, various glands) is called the autonomic or autonomic nervous system. The autonomic nervous system regulates the functioning of organs, precisely adapting their activity to environmental conditions and the body’s own needs.
The autonomic reflex arc consists of three links: sensitive, intercalary and executive. The autonomic nervous system is divided into sympathetic and parasympathetic divisions. The sympathetic autonomic nervous system is connected to the spinal cord, where the bodies of the first neurons are located, the processes of which end in the nerve nodes of the two sympathetic chains located on either side of the front of the spine. The sympathetic nerve ganglia contains the bodies of second neurons, the processes of which directly innervate the working organs. The sympathetic nervous system enhances metabolism, increases the excitability of most tissues, and mobilizes the body's forces for vigorous activity.
The parasympathetic part of the autonomic nervous system is formed by several nerves that arise from the medulla oblongata and from the lower part of the spinal cord. The parasympathetic nodes, where the bodies of the second neurons are located, are located in the organs whose activity they influence. Most organs are innervated by both the sympathetic and parasympathetic nervous systems. The parasympathetic nervous system helps restore spent energy reserves and regulates the body’s vital functions during sleep.
The cerebral cortex forms folds, grooves, and convolutions. The folded structure increases the surface of the cortex and its volume, and therefore the number of neurons forming it. The cortex is responsible for the perception of all information entering the brain (visual, auditory, tactile, gustatory), for the control of all complex muscle movements. It is with the functions of the cortex that mental and speech activity and memory are connected.
The cerebral cortex consists of four lobes: frontal, parietal, temporal and occipital. The occipital lobe contains visual areas responsible for the perception of visual signals. The auditory areas responsible for the perception of sounds are located in the temporal lobes. The parietal lobe is a sensitive center that receives information coming from the skin, bones, joints, and muscles. The frontal lobe of the brain is responsible for drawing up behavioral programs and managing work activities. The development of the frontal areas of the cortex is associated with a high level of human mental abilities compared to animals. The human brain contains structures that animals do not have - the speech center. In humans, there is a specialization of the hemispheres - many higher functions of the brain are performed by one of them. In right-handed people, the left hemisphere contains the auditory and motor speech centers. They provide oral perception and the formation of oral and written speech.
The left hemisphere is responsible for the implementation of mathematical operations and the thinking process. The right hemisphere is responsible for recognizing people by voice and for the perception of music, recognition of human faces and is responsible for musical and artistic creativity - it participates in the processes of imaginative thinking.
The central nervous system constantly controls the functioning of the heart through nerve impulses. Inside the cavities of the heart itself and in. The walls of large vessels contain nerve endings - receptors that perceive pressure fluctuations in the heart and blood vessels. Impulses from the receptors cause reflexes that affect the functioning of the heart. There are two types of nervous influences on the heart: some are inhibitory (reducing the heart rate), others are accelerating.
Impulses are transmitted to the heart along nerve fibers from nerve centers located in the medulla oblongata and spinal cord.
Influences that weaken the work of the heart are transmitted through the parasympathetic nerves, and those that enhance its work are transmitted through the sympathetic ones. The activity of the heart is also influenced by humoral regulation. Adrenaline is an adrenal hormone that, even in very small doses, enhances the work of the heart. Thus, pain causes the release of several micrograms of adrenaline into the blood, which significantly changes the activity of the heart. In practice, adrenaline is sometimes injected into a stopped heart to force it to contract. An increase in the content of potassium salts in the blood depresses, and calcium increases the work of the heart. A substance that inhibits the work of the heart is acetylcholine. The heart is sensitive even to a dose of 0.0000001 mg, which clearly slows down its rhythm. Nervous and humoral regulation together ensure a very precise adaptation of the activity of the heart to environmental conditions.
The consistency and rhythm of contractions and relaxations of the respiratory muscles are determined by impulses arriving through the nerves from the respiratory center of the medulla oblongata. THEM. Sechenov in 1882 established that approximately every 4 seconds, excitations automatically arise in the respiratory center, ensuring the alternation of inhalation and exhalation.
The respiratory center changes the depth and frequency of respiratory movements, ensuring optimal levels of gases in the blood.
Humoral regulation of breathing is that an increase in the concentration of carbon dioxide in the blood excites the respiratory center - the frequency and depth of breathing increase, and a decrease in CO2 reduces the excitability of the respiratory center - the frequency and depth of breathing decreases.
Many physiological functions of the body are regulated by hormones. Hormones are highly active substances produced by the endocrine glands. Endocrine glands do not have excretory ducts. Each secretory cell of the gland is in contact with the wall of the blood vessel with its surface. This allows hormones to pass directly into the blood. Hormones are produced in small quantities, but remain active for a long time and are distributed throughout the body through the bloodstream.
The pancreatic hormone, insulin, plays an important role in regulating metabolism. An increase in blood glucose levels serves as a signal for the release of new portions of insulin. Under its influence, the use of glucose by all tissues of the body increases. Some of the glucose is converted into the reserve substance glycogen, which is deposited in the liver and muscles. Insulin in the body is destroyed quickly enough, so its release into the blood must be regular.
Thyroid hormones, the main one being thyroxine, regulate metabolism. The level of oxygen consumption by all organs and tissues of the body depends on their quantity in the blood. Increased production of thyroid hormones leads to increased metabolic rate. This is manifested in an increase in body temperature, more complete absorption of foods, increased breakdown of proteins, fats, carbohydrates, and rapid and intense body growth. A decrease in the activity of the thyroid gland leads to myxedema: oxidative processes in tissues decrease, the temperature drops, obesity develops, and the excitability of the nervous system decreases. When the activity of the thyroid gland increases, the level of metabolic processes increases: heart rate, blood pressure, and excitability of the nervous system increase. The person becomes irritable and gets tired quickly. These are signs of Graves' disease.
Hormones of the adrenal glands are paired glands located on the upper surface of the kidneys. They consist of two layers: the outer cortex and the inner medulla. The adrenal glands produce a number of hormones. Cortical hormones regulate the metabolism of sodium, potassium, proteins, and carbohydrates. The medulla produces the hormone norepinephrine and adrenaline. These hormones regulate the metabolism of carbohydrates and fats, the activity of the cardiovascular system, skeletal muscles and the muscles of internal organs. The production of adrenaline is important for the emergency preparation of responses of the body that finds itself in a critical situation due to a sudden increase in physical or mental stress. Adrenaline provides an increase in blood sugar, increased cardiac activity and muscle performance.
Hormones of the hypothalamus and pituitary gland. The hypothalamus is a special section of the diencephalon, and the pituitary gland is a cerebral appendage located on the lower surface of the brain. The hypothalamus and pituitary gland form a single hypothalamic-pituitary system, and their hormones are called neurohormones. It ensures the constancy of blood composition and the necessary level of metabolism. The hypothalamus regulates the functions of the pituitary gland, which controls the activity of the other endocrine glands: thyroid, pancreas, genitals, adrenal glands. The operation of this system is based on the principle of feedback, an example of the close unification of the nervous and humoral methods of regulating the functions of our body.
Sex hormones are produced by the sex glands, which also perform the function of exocrine glands.
Male sex hormones regulate the growth and development of the body, the appearance of secondary sexual characteristics - the growth of a mustache, the development of characteristic hairiness in other parts of the body, a deepening of the voice, and changes in physique.
Female sex hormones regulate the development of secondary sexual characteristics in women - a high-pitched voice, rounded body shape, the development of the mammary glands, and control sexual cycles, pregnancy and childbirth. Both types of hormones are produced in both men and women.
The complex structure of the human body is currently the pinnacle of evolutionary transformations. Such a system requires special methods of coordination. Humoral regulation is carried out with the help of hormones. But the nervous system represents the coordination of activities using the organ system of the same name.
What is regulation of body functions
The human body has a very complex structure. From cells to organ systems, it is an interconnected system, for the normal functioning of which a clear regulatory mechanism must be created. It is carried out in two ways. The first method is the fastest. It's called neural regulation. This process is implemented by the system of the same name. There is a misconception that humoral regulation is carried out with the help of nerve impulses. However, this is not at all true. Humoral regulation is carried out with the help of hormones that enter the body fluids.
Features of nervous regulation
This system includes a central and peripheral section. If the humoral regulation of body functions is carried out with the help of chemicals, then this method represents a “transport highway” connecting the body into a single whole. This process happens quite quickly. Just imagine that you touched a hot iron with your hand or stepped out into the snow barefoot in winter. The body's reaction will be almost instantaneous. This is of utmost protective importance and promotes both adaptation and survival in various conditions. The nervous system underlies the innate and acquired reactions of the body. The first are unconditioned reflexes. These include breathing, sucking, and blinking. And over time, a person develops acquired reactions. These are unconditioned reflexes.
Features of humoral regulation
Humoral is carried out with the help of specialized organs. They are called glands and are combined into a separate system called the endocrine system. These organs are formed by a special type of epithelial tissue and are capable of regeneration. The effect of hormones is long-term and continues throughout a person’s life.
What are hormones
The glands secrete hormones. Due to their special structure, these substances accelerate or normalize various physiological processes in the body. For example, at the base of the brain is the pituitary gland. It produces as a result of which the human body increases in size for more than twenty years.
Glands: features of structure and functioning
So, humoral regulation in the body is carried out with the help of special organs - glands. They ensure the constancy of the internal environment, or homeostasis. Their action is in the nature of feedback. For example, such an important indicator for the body as blood sugar level is regulated by the hormone insulin at the upper limit and glucagon at the lower limit. This is the mechanism of action of the endocrine system.
Exocrine glands
Humoral regulation is carried out with the help of glands. However, depending on the structural features, these organs are combined into three groups: external (exocrine), internal (endocrine) and mixed secretion. Examples of the first group are salivary, sebaceous and lacrimal. They are characterized by the presence of their own excretory ducts. Exocrine glands are secreted on the surface of the skin or in the body cavity.
Endocrine glands
Endocrine glands secrete hormones into the blood. They do not have their own excretory ducts, so humoral regulation is carried out using body fluids. Once in the blood or lymph, they spread throughout the body, reaching every cell. And the result of this is the acceleration or slowdown of various processes. This may be growth, sexual and psychological development, metabolism, the activity of individual organs and their systems.
Hypo- and hyperfunctions of the endocrine glands
The activity of each endocrine gland has “two sides of the coin.” Let's look at this with specific examples. If the pituitary gland secretes an excess amount of growth hormone, gigantism develops, and if there is a deficiency of this substance, dwarfism occurs. Both are deviations from normal development.
The thyroid gland secretes several hormones at once. These are thyroxine, calcitonin and triiodothyronine. When their quantity is insufficient, infants develop cretinism, which manifests itself in mental retardation. If hypofunction manifests itself in adulthood, it is accompanied by swelling of the mucous membrane and subcutaneous tissue, hair loss and drowsiness. If the amount of hormones in this gland exceeds the normal limit, a person may develop Graves' disease. It manifests itself in increased excitability of the nervous system, trembling of the limbs, and causeless anxiety. All this inevitably leads to emaciation and loss of vitality.
The endocrine glands also include the parathyroid, thymus and adrenal glands. The latter glands secrete the hormone adrenaline during a stressful situation. Its presence in the blood ensures the mobilization of all vital forces and the ability to adapt and survive in non-standard conditions for the body. First of all, this is expressed in providing the muscular system with the necessary amount of energy. The reverse-acting hormone, which is also secreted by the adrenal glands, is called norepinephrine. It is also of utmost importance for the body, since it protects it from excessive excitability, loss of strength, energy, and rapid wear and tear. This is another example of the reverse action of the human endocrine system.
Glands of mixed secretion
These include the pancreas and gonads. The principle of their operation is twofold. two types at once and glucagon. They, accordingly, lower and increase blood glucose levels. In a healthy human body, this regulation goes unnoticed. However, when this function is disrupted, a serious disease occurs, which is called diabetes mellitus. People with this diagnosis need artificial insulin administration. As an exocrine gland, the pancreas secretes digestive juice. This substance is secreted into the first section of the small intestine - the duodenum. Under its influence, the process of splitting complex biopolymers into simple ones occurs there. It is in this section that proteins and lipids are broken down into their component parts.
The gonads also secrete various hormones. These are male testosterone and female estrogen. These substances begin to act as early as during embryonic development, sex hormones influence the formation of sex, and then form certain sexual characteristics. As exocrine glands, they form gametes. Man, like all mammals, is a dioecious organism. Its reproductive system has a general structural plan and is represented by the gonads, their ducts and the cells themselves. In women, these are paired ovaries with their ducts and eggs. In men, the reproductive system consists of testes, excretory ducts and sperm cells. In this case, these glands act as exocrine glands.
Nervous and humoral regulation are closely interconnected. They work as a single mechanism. Humoral is more ancient in origin, has a long-term effect and affects the entire body, since hormones are carried by the blood and reach every cell. And the nervous system works pointwise, at a specific time and in a certain place, according to the “here and now” principle. Once the conditions change, it will cease to apply.
So, the humoral regulation of physiological processes is carried out using the endocrine system. These organs are capable of releasing special biologically active substances called hormones into liquid environments.
The nervous system regulates the body's activity by changing the strength and frequency of bioelectric impulses. The activity of the nervous system is based on the processes of excitation and inhibition that occur in nerve cells. Excitation is the active state of cells when they transform and transmit electrical impulses to other cells; inhibition is a reverse process aimed at reducing electrical activity and restoration. The central nervous system regulates and controls human motor activity. In the process of physical training, it improves, more subtly carrying out the interaction of the processes of excitation and inhibition of various nerve centers that regulate the work of many muscle groups and functional systems. Training helps the sense organs to carry out motor actions in a more differentiated manner, forms the ability to learn new motor skills and improve existing ones.
Endocrine glands, or endocrine glands, produce special biological substances - hormones. Hormones provide humoral (through blood, lymph, interstitial fluid) regulation of physiological processes in the body, reaching all organs and tissues. Some hormones are produced only during certain periods, while most are produced throughout a person’s life. They can inhibit or accelerate the growth of the body, puberty, physical and mental development, regulate metabolism and energy, and the activity of internal organs. The endocrine glands include: thyroid, parathyroid, goiter, adrenal glands, pancreas, pituitary gland, gonads and a number of others. Some of the listed glands produce, in addition to hormones, secretory substances(for example, the pancreas participates in the digestion process, secreting secretions into the duodenum; the product of external secretion of the male gonads - the testicles - is sperm, etc.). Such. the glands are called glands of mixed secretion. Hormones, as substances of high biological activity, despite extremely low concentrations in the blood, are capable of causing significant changes in the state of the body, in particular in the implementation of metabolism and energy. They have a remote effect and are characterized by specificity, which is expressed in two forms: some hormones (for example, sex hormones) affect only the function of certain organs and tissues, others control only certain changes in the chain of metabolic processes and in the activity of enzymes regulating these processes. Hormones are destroyed relatively quickly and in order to maintain a certain amount of them in the blood it is necessary that they be tirelessly secreted by the corresponding gland. Almost all disorders of the activity of the endocrine glands cause a decrease in the overall performance of a person. The function of the endocrine glands is regulated by the central nervous system; the nervous and humoral effects on various organs, tissues and their functions are a manifestation of a unified system of neurohumoral regulation of body functions.
At a more subtle, molecular level inside the body, there are systems that feel more subtly and know better how to maintain the constancy of the internal environment in the changing conditions of the external environment. Regulation of body functions occurs with the help of two important systems - nervous and humoral. These are two “pillars” that maintain the constancy of the body and contribute to the body’s adequate response to one or another external action. What are these two “whales”? How do they regulate the functioning of the heart and other body functions? Let's look at these issues in detail and in detail.
1 Coordinator No. 1 - nervous regulation
It was previously discussed that the heart has autonomy - the ability to independently reproduce impulses. And so it is. To some extent, the heart is “its own master,” but the activity of the heart, like the work of other internal organs, responds very sensitively to the regulation of the overlying departments, namely to nervous regulation. This regulation is carried out by a division of the nervous system called the autonomic nervous system (ANS).
The ANS includes two important components: the sympathetic and parasympathetic divisions. These departments, like day and night, have opposite effects on the action of internal organs, but both departments are equally important for the body as a whole. Let's consider how nervous regulation affects the functioning of the heart, blood pressure, and the tone of arterial vessels.
2 Sympathetic activity
The sympathetic division of the ANS consists of a central part, located in the spinal cord, and a peripheral part, which is located directly in the ganglia - nerve nodes. Sympathetic control is exercised by the pituitary gland, hypothalamus, vasomotor center of the medulla oblongata, as well as the cerebral cortex. All these regulatory bodies are interconnected and do not work without each other. When is the sympathetic department activated and how does it manifest itself?
A surge of emotions, surging feelings, fear, shame, pain - and now the heart is ready to jump out of the chest, and blood is pulsating in the temples... This is all a manifestation of the effects of sympathy on the work of the heart and the regulation of vascular tone. Also in the walls of arterial vessels there are peripheral receptors that transmit signals to overlying structures when blood pressure decreases; in this case, sympathetic regulation “forces” the vessels to increase tone - and the pressure is normalized.
Based on these data, we can conclude that impulses to the sympathetic departments can come both from the periphery - the vessels, and from the center - the cerebral cortex. In both cases, the answer will arrive immediately. And what will be the answer? The effects of sympathy on the functioning of the heart and blood vessels have an effect with the sign: “+”. What does this mean? Increased heart rate, increased depth and strength of contractions, increased blood pressure, and increased vascular tone.
The heart rate in a healthy heart is set by the SA node; sympathetic fibers cause this node to produce a greater number of impulses, due to which the heart rate increases. Since sympathetic fibers innervate the ventricles of the heart to a greater extent, the strength and frequency of ventricular contractions will increase, and less time will be spent on their relaxation. Thus, sympathetic nervous regulation mobilizes the work of the heart and blood vessels by increasing their tone and increasing the strength, frequency, and depth of cardiac impulses.
3 Parasympathetic activity
The opposite effect is exerted by another department of the ANS - parasympathetic. Let's imagine: you had a delicious lunch and lay down to rest, your body is relaxed, warmth is spreading throughout your body, you are half asleep... How many beats per minute will your heart perform at this moment? Will the blood pressure be high? No. When you rest, your heart rests. During rest, the kingdom of the vagus begins. N.vagi is the most important and largest nerve of the parasympathetic system.
The action of parasympathetics has an inhibitory effect on the functioning of the heart and blood vessels, an effect with a “-” sign. Namely: the frequency and strength of heart contractions slows down, blood pressure decreases, and vascular tone decreases. Parasympathetic activity is maximum during sleep, rest, and relaxation. Thus, the two departments support cardiac activity, regulate its main indicators, and work harmoniously and clearly under the control of overlying structures of the nervous system.
4 Coordinator No. 2 - humoral regulation
People who know Latin understand the meaning of the word “humoral”. If translated literally, humor is moisture, moist, related to blood and lymph. Humoral regulation of body functions is carried out with the help of blood, biological fluids, or rather, it is provided by substances that circulate in the blood. These substances that perform a humoral function are known to everyone. These are hormones. They are produced by the endocrine glands and enter the tissue fluid, as well as the blood. Reaching organs and tissues, hormones have a certain effect on them.
Hormones are extremely active, and they are also specific, since their action is aimed at certain cells, tissues, and organs. But hormones are quickly destroyed, so they must enter the blood constantly. Humoral regulation is carried out with the help of an important, main gland in the cranial cavity - the pituitary gland. He is the “king” of other glands of the body. Specifically, the heart is affected by hormones produced by the adrenal glands, the thyroid gland, sex hormones, as well as substances produced by heart cells.
5 Substances that make the heart work
Adrenaline and norepinephrine. Adrenal hormones. They are produced in large quantities in extreme situations, during stress and anxiety. They increase the frequency and strength of heart contractions, increase blood pressure, and mobilize all body functions.
Thyroxine. Thyroid hormone. Increases heart rate. In people with excessive function of this gland and with an increased concentration of this substance in the blood, tachycardia is always observed - a heart rate of more than 100 per minute. Thyroxine also increases the sensitivity of heart cells to other substances that affect the humoral regulation of the functions of the cardiovascular system, such as adrenaline.
Sex hormones. Strengthen cardiac activity and maintain blood vessel tone.
Serotonin or the “happiness” hormone. Is it worth describing its effect? Everyone knows how the heart jumps out of the chest and beats with happiness?
Prostaglandins and histamine have a stimulating effect, “pushing” the heart.
6 Relaxing substances
Acetylcholine. Its influence has effects on the heart with a “-” sign: the frequency and strength of contractions decreases, the heart “works” less intensely.
Atrial hormones. Atrial cells produce their own substances that have an effect on the heart and blood vessels. These substances include natriuretic hormone; it has a pronounced dilating effect on blood vessels, reduces their tone, also causing a decrease in blood pressure. This substance also has a blocking effect on the activity of the sympathetic nervous system and the release of adrenaline and norepinephrine.
7 Ions in the work of the heart
The concentration of ions or electrolytes in the blood has a great influence on heart contractions. We are talking about K+, Na+, Ca2+.
Calcium. The most important ion involved in cardiac contraction. Provides normal myocardial contractility. Ca2+ ions enhance cardiac activity. Excess calcium, as well as its deficiency, negatively affects the functioning of the heart; various arrhythmias or even cardiac arrest may occur.
Potassium. K+ ions in their excess slow down cardiac activity, reduce the depth of contraction, and reduce excitability. With a significant increase in concentration, conduction disturbances and cardiac arrest are possible. With a lack of K+, the heart also experiences negative effects in the form of arrhythmias and dysfunction. Electrolyte indicators in the blood are contained at a certain level, the indicators of which are established for each ion (potassium norms are 3.3-5.5, and calcium norms are 2.1-2.65 mmol/l). These indicators of humoral function are strictly defined, and if any of them goes beyond the norm, it threatens to cause disruption not only in the heart, but also in other organs.
8 One whole
Both regulatory systems, nervous and humoral, are inextricably linked. It is impossible to separate one from the other, just as it is impossible in a single organism to distinguish between the functions of the right and left hands, for example. Some authors even call these systems in one word: neurohumoral regulation. This emphasizes their interconnection and unity. After all, managing the body is not an easy task and we can only cope with it together.
It is impossible to distinguish among the regulatory mechanisms the main and secondary ones; they are all equally important. We can only state some features of their work. Thus, nervous regulation is characterized by rapid response. Along the nerves, as if through wires, the impulse travels instantly to the organ. But the humoral regulation of functions is characterized by a slower onset of effect, because it takes time for the substance to reach the organ through the blood.