Plan

► Concept of nerve center. Two interpretations of nerve center.

► Properties of nerve centers.

► Coordination in the nervous system. Role of inhibition in coordination mechanisms.

► Kinds of inhibition in the central nervous system.

► Principles of coordination.

Concept of ?Nerve Center" Two tendencies in Interpretation of Nerve Center

Historically there exist two interpretations of the concept of nerve center: narrow-localistic and broad interpretation.

Narrow-localistic interpretation is associated with the works of well-known French physiologist M. Flourens (1842), who showed that a nerve center responsible for neuro-reflex regulation of respiration in birds, is located in the medulla oblongata. A similar point of view was expressed by Russian scientist N. Mislavsky (1885). According to supporters of the narrow-localistic approach, a nerve center is a complex of neurons localized in a specific region of the CNS and responsible for realization of a specific reflex.

Broad interpretation of the concept of nerve center was proposed by representatives of Russian physiological school (I. Pavlov, 1923, P. Anokhin, 1968, and some others). According to the followers of this viewpoint, a nerve center is a complex of neurons represented at different levels of the CNS and interrelated to control a specific physiological function. Broad interpretation of nerve center can be demonstrated on an example of the respiratory nerve center.

Effector organs in the respiratory system are respiratory muscles, which change the volume of thoracic cavity - the diaphragm and external oblique intercostal muscles. Motor neurons supplying these muscles are located in the spinal cord. So, speaking about the respiratory nerve center, it is necessary to mention these groups of neurons in the spinal cord. Spinal motor neurons are under control of neurons of the respiratory center proper in the medulla oblongata. Motor neurons of the medullary respiratory center are in turn controlled by neurons of the pons (a pneumotaxic respiratory center), of hypothalamic centers and of cortical centers. Thus, the optimal control of respiration is provided by the above mentioned nerve centers located on different levels of the CNS, which interact with each other and form a specific hierarchial structure.