Neural Control & Coordination

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1.

Afferent (sensory) fibres: Carry impulses from sense organs to CNS.

2.

Efferent (motor) fibres: Carry impulses from CNS to muscles and glands.

PNS has 2 divisions. They are :

1.

Somatic neural system: Relays impulses from the CNS to skeletal muscles.

2.

Autonomic neural system: Transmits impulses from CNS to involuntary

organs & smooth muscles.

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It includes sympathetic & para-sympathetic nerves. Sympathetic

system prepares body to cope with emergencies, stresses & dangers.

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It increases heartbeat, breathing rate, constricts arteries and elevates BP.

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Parasympathetic system returns the body to a resting state after stressful

situations and slows down heartbeat, dilates arteries, lowers BP etc.

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Visceral nervous system is the part of PNS.

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It includes nerves, fibres, ganglia & plexus by which impulses travel from

CNS to the viscera and from viscera to CNS.

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Unipolar: One axon. No

dendrites. Found in embryo.

Multipolar: One axon and

2 or more dendrites. Most

common type. Found in the

cerebral cortex.

Bipolar: One axon and

one dendrite. Found in the

retina.

Pseudounipolar neurons: A

single process arises from

the cyton and then divides

into axon and dendrite. These

are found in the dorsal root

ganglia of spinal nerves.

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MYELINATED AXON

NON - MYELINATED AXON

Schwann cells are present but

with no myelin sheath. The

grey coloured area without

myelin sheath is called grey

matter. Found in autonomous

& somatic neural systems.

It is enveloped with Schwann

cells that form a myelin sheath

around the axon. (NEET 2017)

Found in spinal & cranial nerves.

The white colored area, formed of

myelinated nerve fibres is called

white matter. Gaps between 2

adjacent myelin sheaths are

called nodes of Ranvier.