Signaling Hormonal and nervous regulation

Signaling. Hormonal and nervous regulation

Signaling is necessary to coordinate the behavior and interaction of organisms, as well as organs and cells within the body.

Animals primarily use odors, that is, chemical signaling. Odorous substances - various molecules - are excreted in animals by skin glands, with exhaled air, with urine and other liquids, and in plants with leaves, bark, flowers. Odors are perceived in various animals by olfactory organs or diffusely scattered in the integument by chemoreceptor cells. There are, on the one hand, attractants - attracting substances, including pheromones - attracting a sexual partner, on the other - repellents - repellent substances. Attractants and repellents are very effective in the fight against harmful insects, snails, rodents and other animals. Their range can reach several kilometers. Fragrant herbs, oils have been used since ancient times.

Many organisms use light to communicate. Glow possess some bacteria, fungi, protozoa, jellyfish, crustaceans, insects, fish.

Special substances - phosphors emit portions of light energy under the action of short-wave radiation, an electric discharge or a chemical reaction. This phenomenon, called luminescence, is also known in inanimate nature - for example, the glow of white phosphorus, sulfide compounds of calcium, barium, strontium. Bioluminescence is used by various organisms to illuminate and lure prey, scare away predators, and attract a sexual partner.

Sounds, postures, and gestures are also important in signaling in animals. In human evolution, these forms of signaling became leading. Attaching special importance to speech as a form of communication between people, Academician I.P. Pavlov called it the second signal system, opposing all other signals, united in the concept of the first signal system. The peculiarity of speech as a signaling method is that words contain a generalization of countless signals of the first signaling system, and thus words become “signals of signals”. Speech is one of the manifestations and at the same time an instrument of a person's higher nervous activity (see below).

Inside the body, hormonal and nervous mechanisms of regulation are used for interaction between organs, tissues and individual cells and for the perception of signals from the outside world.

Hormonal regulation is carried out with the help of biologically active substances, among which hormones play the main role (from the Greek hormao - I encourage, set in motion). Hormones are secreted into the blood by special endocrine glands, or endocrine glands (pituitary, adrenal, thyroid, pancreas, sex and other glands). Delivery of hormones to target organs is also carried out through the liquid media of the body - blood, lymph and intercellular fluids, therefore this signaling mechanism is called humoral (from the Latin humor - liquid). The endocrine system is under the control of the central nervous system. Therefore, nervous excitement always turns into a wave of hormonal influences that mobilize the body for an adequate response. For example, in stressful situations (fear, physical overload), the adrenal glands release the hormone adrenaline into the bloodstream, which dramatically increases oxygen consumption and blood glucose concentration, which in turn leads to an increase in energy production. Thus, a unified neurohormonal regulation is actually implemented.

Most hormones are chemically peptides (small proteins), there are also steroids (from the class of lipids) and monoamines (transformed amino acids). Each hormone acts on specific target cells or several types of cells. The perception of the hormonal signal is carried out by special receptor molecules (glycoproteins or glycolipids) located in the membrane or in the cytoplasm of the cell (figure). An excited receptor, catalyzing a chain of chemical reactions, transmits a signal further - to the working structures of the cell. As a result, there is a response in the form of secretion (release of active substances), specific syntheses, reproduction and growth of cells. Thus, hormones are involved in the regulation of the functioning, growth and development of the body.

Nervous regulation occurs with the help of special nerve cells (neurons) that have long processes and are connected into nerve circuits or networks of varying complexity.

Nervous regulation is already present in hydras and jellyfish - the simplest multicellular animals, and reaches its highest development in vertebrates, especially in humans with their developed brain and spinal cord, the vegetative system of ganglia and local accumulations of neurons in internal organs. Literally every part of the body is permeated with nerve processes and their branched endings, which allows the body to have information about the state of environmental conditions at all its points and manage these conditions - as a rule, with the participation of hormonal regulation. On the basis of neural connections, complex programs of internal regulation of organs, behavior and higher nervous activity are formed.

The most complex manifestation of higher nervous activity in humans is consciousness as the highest level of mental activity. The most important function of consciousness is thinking with its main operations of abstraction, generalization, mediation, etc. Thinking is aimed at understanding the essence of objects and phenomena, creating new ideas, mentally constructing actions, and foreseeing their consequences. Thinking is the highest form of active reflection of objective reality. Is modern science able to explain the nature of the nervous activity, to understand the subtle mechanisms of the brain? Many questions and blank spots remain in neurobiology since we are talking about the most complex form of manifestation of life, but elementary processes have been studied quite well. As mentioned above, the structural unit of the nervous tissue is a nerve cell - a neuron. Neurons have numerous branched connections, especially complex in the cerebral cortex. Connections extend, on the one hand, to sensitive receptors (skin, visual, auditory, olfactory, receptors of internal organs), and on the other hand, to all regulated executive organs (muscles, digestive tract, glands, etc.). An elementary phenomenon in nervous regulation is a reflex - a response of an organ (organism) to external or internal irritation, carried out through the nervous system (Fig. 10). The idea of ​​reflexes was put forward as early as the 17th century by the French naturalist and philosopher R. Descartes, who attributed them to automatic involuntary actions. Russian physiologist I.M. Sechenov in 1863 asserted that "all acts of conscious and unconscious life are, by way of origin, reflexes." In the 20th century, this concept was developed by I.P. Pavlov in the doctrine of unconditioned and conditioned reflexes. Numerous and varied reflexes are combined into complex behavioral acts, instincts, and all higher nervous activity develops on their basis. In lower animals, hereditarily fixed unconditioned reflexes predominate, while in humans, acquired conditioned reflexes dominate, fixed in the processes of training, education, and labor activity.

Known and biophysical principles of neurons. Along the processes of neurons, signals can be transmitted over long distances in hundredths of a second. Touch a hot object with your hand - a reflex response will immediately follow. And, by the way, the signal has time to run along the sensitive nerve fibers from the fingers to the spinal ganglia and further to the spinal cord, switch to other nerve cells and return to the muscles that pull the hand away from the hot object (see figure). It has been established that signal transmission along the nerve fiber is carried out using electric currents and electromagnetic fields generated in the surface membrane of the neuron.

Consider the scheme of generation and conduction of a nerve impulse.

Initially, due to the work of ion pumps (active ion transport), a potential difference accumulates on the membrane of a nerve cell (plus outside, minus inside), reaching 80 millivolts.

The main carrier of an external positive charge is sodium ions. When a section of the membrane is irritated, protein pores open, through which sodium ions rush into the cell (according to the law of simple diffusion). The flow of charged particles, in this case, the flow of sodium ions through the water-protein channel, represents an electric current. As is well known, an electric current generates an electromagnetic field around a conductor; the same thing happens in an electric motor on the rotor windings. The emerging electromagnetic field is immediately transferred to the neighboring protein pores, opening them for sodium ions.

A chain reaction is generated from one pore to another, which spreads along the entire nerve fiber. The transmission of the nerve impulse is completed by irritation of the membrane at the tip of the fiber and the release of a portion of the mediator - a substance that excites the next cell. If it is a muscle cell, a contractile reaction involving microfilaments and myosin will follow. In the somatic nervous system, signals travel especially quickly, since large sections of fibers are covered with the so-called myelin sheath, and the electromagnetic field "jumps" through these areas, and does not "creep" through all the pores of the membrane. The situation is comparable to that when a horse under a rider or a predator chasing prey changes from a trot to a gallop.

Note that other tissues also have electrical excitability and conductivity, in particular the muscle bundles of the heart. This allows you to organize its rhythmic, uninterrupted and, to a certain extent, autonomous operation. In the event of a cardiac arrest, if no severe structural disturbances have occurred in it, it is possible to restore work with electric current discharges, which is done in emergency medicine.

The electrical activity of the conductors of the brain, heart and other organs is added to a certain total biofield of each individual organ and the whole organism.

This electromagnetic field is easily recorded and serves as a valuable diagnostic feature in the detection of diseases of the heart and brain (electrocardiography, electroencephalography). Particularly sensitive people - psychics - are able to capture vibrations of someone else's biofield with their receptors and even make some diagnoses.

From the consideration of the mechanisms of biological signaling, it is clear that they are based on elementary physical and chemical processes. Protein-carbohydrate receptors of cell membranes stereochemically recognize various signal molecules - attractants and repellents, hormones, and mediators. The perception of light, and hence visual images, is based on electromagnetic excitation of protein receptors in the membranes of light-sensitive cells - cones and rods - in the retina. In all cases, the reacting molecules undergo reversible conformational denaturation. Enzymatic reactions are often involved in signal transduction, where conformational rearrangement is also a working moment. Almost all signaling and regulatory processes occur with the expenditure of energy. Solar energy in plant cells generates the synthesis of glucose,

From the macroregion bonds of ATP, energy passes into work - it turns into other chemical bonds, into electrical, light, mechanical energy and is dissipated into space in the form of residual heat. Like other types of life, signaling, hormonal and nervous activity represent options for the existence and transformation of matter - matter and fields.

Conclusion on the topic

Life is material, its physical and chemical basis is the metabolism and energy. Matter, including living matter, is an objective reality, it exists outside of consciousness, outside of spirit, regardless of any "life force".

Matter is primary, while consciousness is secondary, derived from matter, that is, it represents a property of living matter, one of the forms of its movement. Motion is a universal property of matter. It is even more than a property - it is her way of being. In this sense, it is impossible to separate the living matter itself and its functional manifestations, including the impossible to separate the living brain and its product - consciousness. Life is a special form of movement of a particularly complex matter, qualitatively (emergently) different from the forms of movement of inorganic matter. This new quality - life - is generated as the sum of the properties of the constituent elements. Quantity turns into quality, the whole is greater than the sum of its parts. Similarly, the forms of organization and movement of social systems are different from the forms of organization and movement of individual living individuals.