Nervous system PPT. part 3

Nerve Tissue & the Nervous system III:
Central Nervous System:
• The principal structures of the CNS are the cerebrum, cerebellum, and spinal cord.
• It has virtually no connective tissue and is therefore a relatively soft, gel-like organ.
• When sectioned ,the cerebrum ,cerebellum, and spinal cord show regions of white (white matter) and gray (gray matter), differences caused by the differential distribution of myelin.
• Gray matter contains abundant neuronal cell bodies, dendrites, the initial unmyelinated portions of axons , astrocytes ,and microglial cells.
• Gray matter is prevalent at the cortex of the cerebrum and cerebellum, whereas white matter is present in more central regions.
Cerebral Cortex: fig.(5)
General Features:
Cerebral cortex consists of grey matter that covers the cerebral hemisphere.
The surface area of the cortex is increased due to the presence of many convolutions or gyri separated by sulci.
The cortex is made of a mixture of nerve cells, fibers, neuroglia and blood vessels.
Types of Nerve Cells
The nerve cells in cerebral cortex are of five types ,they are:
1. Pyramidal cells