Special Histology and Embryology: Practical Course - V. K. Napkhanyuk 2001

Nervous System

The Nervous system integrates Organs and structures that collectively connect the Organism to its external environment, regulate all vital processes, and coordinate and integrate The activity of all its Organ Systems as a unified whole.

Anatomically, the nervous system is divided into the central and peripheral nervous systems. The Central Nervous System comprises the Brain AND SPINAL cord, whereas the Peripheral Nervous System includes peripheral ganglia, nerve trunks, and nerve endings.

From a physiological perspective, the nervous system is subdivided into the somatic nervous system, which innervates the entire body excluding Internal Organs, Blood Vessels, and glands, and the Autonomic (vegetative) nervous system, which regulates the activity of the aforementioned organs. The nervous system operates on a reflex principle, the morphological substrate of which is the reflex arc.

A reflex arc is a chain of Neurons that ensures the conduction of a Nerve Impulse from the receptor of a sensory neuron to the effector ending in a target organ.

The reflex arc of the somatic nervous system can be either simple or complex. A simple reflex arc consists of a sensory neuron of a spinal ganglion, an association neuron, and a spinal motor neuron. A complex reflex arc incorporates multiple association neurons In addition to sensory and effector neurons.