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A Handbook of Biology

Neural (Nervous) system is a system that controls and coordinates the body

activities, conducts and integrates the information and responds to stimuli. It

provides an organized network of point-to-point connections for a quick response.

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It includes brain, spinal cord and nerves.

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It is made up of specialized cells known as neurons.

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Neuron is the structural and functional unit of neural system.

It is composed of :

Cell body (cyton): Contains cytoplasm, cell organelles and Nissl’s

granules (granular bodies made of free ribosomes + RER)(NEET 2018)

Dendron: Short fibres projecting from the cyton. Their sub-branches

(dendrites) transmit impulses towards the cyton.

Axon: A long fibre which transmit impulses away from the cell body.

The branching of axon is called axonite. Each axonite ends as a bulb-like

structure called synaptic knob.

Axon

Cell body

Nissl’s body

Dendrites

Nucleus

Axon terminal

Schwann cell

Myelin sheath

HÜMÅÑ ÑËRVØÜS (ÑËÜRÅL) SÝSTËM

It has 2 parts:

1. Central neural system (CNS): Brain &

spinal cord.

2. Peripheral nervous system (PNS):

All

nerves of the body.

PËRÏPHËRÅL ÑËÜRÅL SÝSTËM (PÑS)

It includes cranial nerves and spinal nerves. Nerve fibres of PNS are 2 types: