Nervous tissue is organized into two basic systems. They are, “ the Central Nervous System and the Peripheral Nervous System. The peripheral system responds to stimuli and sends impulses to the central system (brain and spinal cord). These impulses are interpreted by the CNS and then other impulses initiated in the CNS travel back through the PNS to effector organs to produce the proper response.”
Neuron is the basic cell of the nervous system. Its structure is, “the cell body, containing the nucleus and synthetic organelles. the axon, a long cytoplasmic process associated with the cell body used to communicate with target organs. and the dendrites, shorter cytoplasmic processes of the cell body used to communicate between neurons.”
Central Nervous System
Spinal Cord consists of gray and white matter. Gray matter consists of nerve cell bodies. The white matter is composed of axonal projections and they surround gray matter. Brain too has gray and white matter. In some parts, an additional outer gray layer exists that has well-defined functions.
This starts at the surface of the cortex and moves inward. The first three layers of the cell bodies are identified thus: superficial molecular layer, containing only a few small cell bodies. outer granular layer, containing small round cell bodies. pyramidal cell layer, containing cell bodies triangular in shape. The other three layers are an inner granular layer, polymorphic cell layer, and the internal pyramid layer.