Principles of coordination of reflex processes (reciprocity; common final path; dominant; subordination; reverse afferentation).

Under the conditions of the physiological norm, the work of all organs and systems of the body is coordinated: the body reacts to influences from the external and internal environment as a whole.

Phenomena of coordination play an important role in the activity of the motor apparatus.

Due to the coordinated work of the nerve centers, the body is perfectly adapted to the conditions of existence.

The principle of reciprocity (conjugation) in the work of nerve centers. Its essence lies in the fact that when some nerve centers are excited, the activity of others can be inhibited. When the flexion center of one limb is excited, reciprocal inhibition of the extension center of the same limb occurs. On the symmetrical side, there are reverse relationships: the extensor center is excited and the flexor center is inhibited. Only with such mutually combined (reciprocal) innervation is the act of walking possible.

The principle of a common final path. Impulses coming to the CNS through different afferent fibers can converge (converge) to the same intercalary, or efferent, neurons. The same motor neuron can be excited by impulses coming from different receptors (visual, auditory, tactile), i.e. participate in many reflex reactions (include in various reflex arcs).

For example, motor neurons that innervate the respiratory muscles, in addition to providing inspiration, are involved in such reflex reactions as sneezing, coughing, etc.

dominance principle. The dominant is a temporarily dominant focus of excitation in the central nervous system, which determines the nature of the body’s response to external and internal stimuli.

The dominant focus of excitation is able to attract (attract) to itself nerve impulses from other nerve centers that are less excited at the moment. Due to these impulses, the activity of the dominant increases even more, and the activity of other nerve centers is suppressed.

Dominants can be of exogenous and endogenous origin. Exogenous dominant occurs under the influence of environmental factors. For example, when reading an interesting book, a person may not hear the music playing on the radio at that time.

Endogenous dominant arises under the influence of factors of the internal environment of the body, mainly hormones and other physiologically active substances. For example, with a decrease in the content of nutrients in the blood, especially glucose, the food center is excited, which is one of the reasons for the food installation of the organism of animals and humans.

The dominant can be inert (persistent), and for its destruction it is necessary to create a new, more powerful focus of excitation.

The dominant underlies the coordination activity of the body, ensuring the behavior of humans and animals in the environment, as well as emotional states, reactions of attention. The formation of conditioned reflexes and their inhibition is also associated with the presence of a dominant focus of excitation.

The principle of subordination (subordination). The main trend in the evolution of the nervous system is manifested in the concentration of the functions of regulation and coordination in the higher parts of the central nervous system – cephalization of the functions of the nervous system. There are hierarchical relationships in the CNS – the highest center of regulation is the cerebral cortex, the basal ganglia, middle, medulla and spinal cord obey its commands.

Feedback principle . This principle was studied by I. M. Sechenov, Sherrington, P. K. Anokhin and a number of other researchers. With reflex contraction of skeletal muscles, proprioreceptors are excited. From proprioreceptors, nerve impulses again enter the central nervous system. This controls the accuracy of the movements made. Similar afferent impulses arising in the body as a result of the reflex activity of organs and tissues (effectors) are called secondary afferent impulses, or feedback.

Feedback can be positive or negative. Positive feedback contributes to the strengthening of reflex reactions, negative – to their oppression.

Due to positive and negative feedbacks, for example, the regulation of the relative constancy of the arterial pressure value is carried out.

Secondary afferent impulses (feedback) also play an important role in the regulation of other autonomic functions: respiration, digestion, excretion.

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