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Reflex is the response of the body to irritation emanating from the external or internal environment with the participation of the nervous system.

Each reflex is carried out using a reflex arc

The reflex arc of the spinal reflex consists, as a rule, of two to three neurons.

Each reflex arc consists of an afferent (sensitive) link beginning with a receptor apparatus and an efferent (motor) link ending with a working organ (effector) Quite often, between two indicated links there are one or two insertion neurons that receive pulses from receptor apparatuses and process them into centrifugal ones impulses going to the executive body.

In the autonomic nervous system, reflex effects can also occur in the presence of only one neuron. This refers to the axon-reflex, carried out without the participation of the central nervous system and representing the excitation of one axon branch with proximal distribution to the branching point and then again distally along its other branch (.

Distinguish between simple and complex, acquired and innate, unconditioned and conditioned reflexes.

Unconditioned reflexes are congenital, hereditarily fixed reflexes developed in the process of phylogenesis, conditioned ones are inconstant, individual reflexes acquired in ontogenesis as a result of the interaction of the organism with the environment, developed on the basis of unconditioned reflexes. In addition to simple unconditioned reflexes, there are such complex unconditioned reflexes as instincts (food, defensive, sexual, parental).

Conditioned reflexes were discovered by I.M.Sechenov; later they were deeply studied by I.P. Pavlov and his school. The study of conditioned reflexes has opened up broad prospects in understanding the functions of the large brain and its most perfect part - the cortex.
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