What does the peripheral nervous system do?

Peripheral nervous system does the following things:

• Controls the movement of the body.
• Controls and co-ordinates various function of the body.

What two systems make up the peripheral  nervous system what do they do?

The two systems that make peripheral nervous system  are as follows:

SOMATIC NERVOUS SYSTEM

The somatic nervous system includes the nerves supplying the skeletal muscle. (Voluntary controls).

The somatic nervous system controls the movement of the body by acting on the skeletal muscles.

The somatic nervous system is composed of two types of nerves. These are:

• Cranial nerves
• Spinal nerves

Cranial Nerves

There are 12 pairs of cranial nerves originating from nuclei in the inferior surface of the brain.

No.	NAME	TYPE	FUNCTIONS
I	Olfactory	Sensory	Smell.
II	Optic	Sensory	Vision, visual information.
III	Oculomotor	Motor	Eye movement, pupil constriction. (Moving   the    eye    ball    medially,    upward    and downward).
IV	Trochlear	Motor	Eye    movement   (Moving   the   eye   ball   downward and outward).
V	Trigeminal	Mixed	Sensation for the face, motor to muscles of   chewing.
VI	Abducent	Motor	Eye movement (Moving eye ball laterally).
VII	Facial	Mixed	Taste sensation, facial expression, secretion   of tear and saliva.
VIII	Vestibulocochlear	Sensory	Hearing, balance
IX	Glossopharyngeal	Mixed	Sense of taste, pharynx movement, secretion   of saliva.
X	Vagus	Mixed	Heart, Lungs, GIT, ear.
XI	Accessory	Motor	Movement of neck, shoulder.
XII	Hypoglossal	Motor	Tongue movement.

Spinal Nerves

The nerves arising from the spinal cord are called spinal nerves. There are 31 pairs of spinal nerves.

These nerves arise from the side of spinal cord by passing through the intervertebral foramina formed by adjacent vertebra. They are:

•  Cervical   –   8 pairs (In neck region)
• Thoracic –   12 pairs (In thorax region)
• Lumbar –    5 pairs (Upper abdomen region)
• Sacral –      5 pairs (Lower abdomen region)
• Coccygeal – 1 pair (In tail region)

The spinal nerves are mixed nerve.

They Carry both sensory (afferent) and motor (efferent) impulses.

AUTONOMIC NERVOUS SYSTEM

The system which controls and co-ordinates various function of the body “automatically” (Independently) are called autonomic nervous system.

It “automatically” controls rate of heart beat, movement of alimentary canal etc.

It is also called visceral nervous system because it innervates the visceral organs.

The activity of autonomic nervous system is controlled by medulla oblongata and hypothalamus.

The autonomic nervous system is  divided  into  two antagonistic divisions.

• Sympathetic nervous system
• Parasympathetic nervous system

Sympathetic nervous system

It is also known as thora columbar outflow because it arises from thoracic and lumbar region of spinal cord (T1-L2).

Parasympathetic nervous system

It is also known as craniosacral outflow because it arises from brain and sacral region of spinal cord.

How to differentiate Sympathetic and Parasympathetic effects?

		Effectors organs			Sympathetic effects	Parasympathetic effects
		Eye			Relaxation Dilation	Contraction Constriction
			Ciliary   muscle
			pupil
		Lacrimal   glands			Decrease            in   secretion	Increase in secretion
		Salivary   secretion			Decrease            in   secretion          and vasoconstriction	Increase in secretion and vasodilation
		Gall bladder			Relaxation	Contraction
		Urinary   bladder			Constriction       of   internal sphincter	Relaxation of internal sphincter
		Sweat glands			Increase              in   secretion	Decrease in secretion
		Heart			Increase  Rate  and   force of heart	Decrease Rate and force of heart
		Blood vessels			Constriction of all   blood vessels except those in heart and skeletal muscle	Dilation
		Bronchioles			Dilation	Constriction

What is central nervous system consist of?

Central nervous system is consist of brain and spinal cord.

What is brain?

Brain is the parts of central nervous system, lies in the cranial cavity. The Average weight of brain is about 1.5kg. The brain consists of the following parts:

• Cerebrum
• Mid brain
• Pons
• Medulla
• Cerebellum

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