Nerve Cell Structure And Function

By Author: Pierce Brosnan
Total Articles: 127
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Introduction to nerve cell structure and function :

A Nerve cell with all its processes is called a neurone.It is the structural and functional unit of the nervous system.A neurone has cell body called soma and two types of processes called axons and dendrites.

NERVE CELL STRUCTURE AND FUNCTION : THE CELL BODY

The nucleated cytoplasmic portion of a neurone is termed cell body or soma.Typically each cell body which may be 4 to 100µm in diameter may be fusiform,pyramidal, pyriform or irregular stellate in shape.Cell body contains a large spherical central nucleus along with large number of Nissl's granules within the cytoplasmic matrix called neuroplasm.The Nissl's granules contain ribonucleoprotein and are involved in protein synthesis.The neuroplasm also contains mitochondria,golgi bodies , melanin , lipochrome pigment granules.The amount of these cell organelles varies with the functional activity of the cell. The cell body is with non functional centrosome because of which neurones cannot divide.Therefore number of neurones present in an adult is same as that present at birth.Delicate ...
... cytoplasmic threads called neurofibrils are present throughout the entire length of axon and dendrites arising from cell body.The cell body and its processes are surrounded externally by a thin membrane ,the neurone membrane.The cell body is present in grey matter of the central nervous system-brain and spinal cord.

NERVE CELL STRUCTURE AND FUNCTION : DENDRITES

The short cytoplasmic processes of cell body which receives stimulus from other neurone are called dendrites.The dendrites conduct nerve impulses induced by stimuli towards the cell body.The dendrites at their origin from cell body are 5-10 µm in thickness but gradually their thickness decreases by profuse branching.

Function: Dendrites receives impulses from axon of another neurone through synapse and conducts the impulse towards the cell body ,therefore it is called the receptive organ.

NERVE CELL STRUCTURE AND FUNCTION : AXON

The long cytoplasmic process of cell body which transmits impulse from cell body to other neurone is termed axon.Axon is considerably longer than dendrites.The axon arises from the cell body in a conical elevation called axon hillock ,which is devoid of nissl's granules.The length of axon is variable and depends on the functional relationship of the neurone.The cytoplasm of axon known as axoplasm contains mitochondria ,neurofibrils but no nissl's granules.The membrane covering axon is called axolemma.Axon can give of branches, called collaters along its course and near the end it undergoes considerable branching into axon terminals or end brush ,the last part of which is enlarged to form end bulb.Axon is present in white matter of central nervous system and peripheral nervous system.The nerve fibres or axon are covered by a lipid rich membrane called myelin sheath.The myelin sheath is formed by schwann cells and each schwann cell covers a part of the nerve fibre.The region where axon is not covered by myelin sheath is the junction of adjacent myelinated segments called node of ranvier.

Function : Axon transmits impulse from cell body of one neurone to dendron of another neurone through synapse.

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