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Today we will discuss about nerve cell shall we start so,
structural and functional unit of neural system
Cell body or cyton or soma or perikaryon
A. Cytoplasm of cyton is uninucleated.
B. Except centriole all the cell organelles are present.
C. Because of the absence of centriole in the nerve cell, cell division is absent.
D. Some other organelles like Nissl's granules and neurofibrils are also found in nerve cell.
Nissl's Granules (Tigroid Body)
A. Nissl's granules are formed by rough endoplasmic reticulum surrounded by clusters of ribosomes.
B. It is the site of protein synthesis.
C. These are stained with a basic dye (methylene blue).
D. Chemically these are ribonucleoprotein.
E. Nissl's granules are present in cell body and dendron where as absent in axon.
Neurofibrils
These are formed in complete neuron.
Many small fibrils are found in the cytoplasm of neuron called neurofibrils. These help in internal conduction in the cyton.
Dendron
Fine branches of dendron are called dendrites.
Short fibres which branch repeatedly and project out of the cell body also contain Nissl's granules and are called dendrites. These fibres transmit impulses towards the cell body.
Axon
Longest cell process of cyton with uniform diameter.
Cytoplasm of axon is called axoplasm.
Nissl's granules are absent in axoplasm.
Covering of axon axolemma
Axoplasm contain neurofibrils and mitochondria.
The axon is a long fibre, the distal end of which is branched. Each branch terminates as a bulb-like structure called synaptic knob which possess synaptic vesicles containing chemicals called neurotransmitters.
The axon transmit nerve impulses away from the cell body to a synapse or to a neuro muscular junction.
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SUHAIL UR REHMAN
Msc Zoology
