The physiological base of the reflection of reality is the reflex arc. It is composed of three parts closely related to this function of reflection: the receptor, or organ of the senses that receives the external excitation and transmit the nervous impulse through an afferent path up to a particular region of the cerebral cortex; a chain of neurons through which the excitation spreads within the central nervous system; and an efferent path made up by nervous cells that give origin to the motor or efector nervous fiber that ends in the muscle or the gland.

This reflex arc constitutes the physiological substratum of the reflex act, or response of the organism to external stimuli by means of the central nervous system. The reflex, thus, constitutes the fundamental form of adaptation of the organism to the environment, and by means of the nervous system the organism relates as a unique whole with the outside world, and at the same time it self regulates in relation to the internal functions of the different organs and systems that comprise it. This reflex type activity permits the organism to adapt itself to the most diverse changes of the environment, and is carried out by the central nervous system and particularly the cerebral cortex.

All brain functions, even the most complex, which are the material base to the psychic phenomena, are performed by reflex acts. These reflexes can be of two types: unconditioned and conditioned.

The unconditioned reflexes are those inborn, present at the moment of birth, more or less invariable, that are produced basically by sections of the central nervous system located beneath the cerebral cortex: subcortex and spinal cord.

These reflexes allow a certain adaptation of the organism to conditions of the environment, and play an indispensable role in the survival of the subject. This adaptation, however, is obtained only within narrow boundaries, because as a rule it is given as a response to a relatively small amount of stimuli, and has a generalized character, not too variable. They are inborn and constant reflexes that allow a relatively imperfect adaptation of the organism to the variable conditions of life.

Then, what brings the child when he is born? He brings a group of unconditioned reflexes that allow his survival, that is:

•  Survival reflexes, directly related to the vital functions of the organism: deglutition, breathing, circulation, excretion, suction, among others.

•  Defense reflexes, or those reflexes that permit avoidance of a noxious irritator.

•  Orientation reflexes, of approximation to a new or unusual stimulus.

•  Atavic or retrogressive reflexes, that express prior periods of phylogenetic development. The grasping reflex, the Moro reflex, and the natatorial reflex, among others.

Of survival reflexes, one of the most important in child's development is the suction reflex, which permit the nourishment of the newborn child. If this reflex does not manifest itself, or if it is manifested with limitations, this may be an indication of problems in development of the child. Because of this, any person working with children must be very much aware of the manifestation of this reflex so as to take the corresponding actions.

The defense reflex allows a newborn baby, in a way, to fight for its survival. If, for example, one takes a pin and punctures the newborn´s arm, it will immediately move it back due to a simple reflex action, without any direct order from the cerebral cortex. The defense reflex is commonly accompanied by immediate cry, which can be the indication that a noxious stimulation is acting upon the baby and compels to give it the most immediate attention.

In opposition to the previous type of reflex, the orientation reflex leads to an active behavior of the organism to approach to any unusual stimulus that come into its visual field. A bright light, a loud noise, attracts the newborn immediately, who moves his face in the direction of the source of stimulus. It is stated that this reflex is the base of the reaction of astonishment, which is characteristic of the child's cognitive interest at the end of the first year of life. According to this, M. Fonarev points out that if this orientation reflex is not properly stimulated, it disappears when the child is two weeks old, naturally losing then an important source for the psychical development of the child. That is why its permanency since the very moment of birth of the child must be stimulated.

Atavic reflexes, as their name point out, refer to all those reflex manifestations that are indications of past periods of the phylogenetic and ontogenetic development, and that remain until a particular moment of development of the individual. Most of the specialized bibliography considers that these reflexes have a “pathognomonic” character, that is, they are indicators of probable pathology when they still remain more time than the expected , as is the case of the Moro reflex or the grasping reflex, which are present during the first months after birth, but they should have disappeared by the end of the third month of life.

However, there are authors, as for example M. Fonarev, in Russia, and L. Cruz, in Cuba that state that these reflexes are important in the development of the child, and that they should be stimulated to guarantee their permanency. Such is the case of the natatorial reflex, which was not stimulated before, and however today is since the very early stages in which children are introduced in swimming pools to swim since the first days after they are born, which determines a permanency of the reflex and makes swimming possible since the earliest ages. Children who have kept this type of reflex by means of stimulation show very outstanding motor characteristics, and in this sense the experiences carried out in Russia are very eloquent.