Desribe in detail the structure of neuron and explain in brief the synapse reflex arc.
Answers
Neuron is the functional unit of nervous system the three main parts of a neuron are the cell body dendrites and axon.
(i).Cell body(perikaryon or cyton):- cell body contains a well defined nucleus surrounded by granular cytoplasm. it has all the cell organelles.Cell body contains a well defined nucleus surrounded by granular cytoplasm. It has all the cell organelles like other cells , only centrosome is absent because nerve cells have lost the ability to divide.
ii).Dendrites(dendron: tree/branch):-
These are branched cytoplasmic projections of the cell body and they conduct nerve impulses to the cyton.
iii).Axon:-
It is a long process from the cell body.
It varies in size from a few millimetres to even more than one metre in length.
In most neurons the axon is surrounded by a white insulating sheath known as myelin sheath which is covered by an outermost thin sheath called neurilemma.
The myelin shows gaps throughout the length which are called nodes of ranvier.
Some axons may have side branches called collaterals.
The end portions of the axons have swollen ends like "bulbs",which store certain chemicals called neurotransmitters such as acetylcholine.
Axon terminals are closely placed near the dendrites of another one or more neurons but are not connected. Such gaps in between are called synaptic clefts.
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Synapse is the point of contact between the terminal branches of the axon of a neuron with the dendrites of another neuron separated by a fine gap.
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Reflex arc is the shortest route that can be taken by an impulse from a receptor to an effector.
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Hope it helps you!!