Function of nerves and types of nervous system

PERIPHERAL NERVOUS SYSTEM:
The peripheral nervous system consists of nerves arising from brain called cranial nerves and from spinal cord called the spinal nerves.
A)CRANIAL NERVES:
There are 12 pairs of cranial nerves in man.These are arising from the ventral side of the brain.Each is given a name according to its distribution.Each is numbered with Roman numerical according to the order in which its superficial origin.The deep origin of a cranial nerve refers to its nuclei of origin and termination of brain.The Nature,distribution and functions of the cranial nerves with branches are as follows:

No. Name with main branches Origin from brain Distribution Nature Function
1 Olfactory Olfactory lobe Olfactory epithelium Sensory Smell
2 Optic Optic chiasma Retina of eyes Sensory Vision
3 Ocumulator Crura cerebri Four muscles of eye ball Motor Eye movement
4 Trochlear Mid brain Superior Oblique Motor Eye movement
5 Trigeminal Pons Varolii Eye,eyelids,tongue Both sensation
6 Abducens Pons Varolii External rectus muscle Motor Eye movement
7 facial Pons Varolii Palate tongue,lower jaw Both Movement salivation
8 Auditory medulla Internal ear cochlea Sensory Equilibrium in hearing
9 Glossopharyngeal Medulla Tongue,pharynx Both Taste,Salivation,Swallowing
10 vagus Medulla Larynx,Heart,lungs Both Movement
11 Spinal accessory Medulla pharynx,larynx,neck Motor Movement
12 Hypoglossal Medulla Neck and tongue motor Movement

Trigeminal is the largest cranial nerve whereas Vagus the longest cranial nerve.Nature of the Cranial nerve can be found out by following statement:
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B)Spinal Nerve:
There are 31 pairs of Spinal nerves.Paired Spinal nerve emerges from sides of spinal cord and find their way through the vertebrae into the corresponding muscle segments.The spinal nerves are as follows:
1)Cervical:8 pairs(neck)
2)thoracic:12 pairs(in thorax)
3)Lumbar :5 pairs(in the upper part of abdomen)
4)Sacral :5 pairs(in the lower part of abdomen)
5)Coccyxgeal:1 pair(in the tail region)
Each spinal nerve carries both sensory and motor impulses.It originates by two roots-a dorsal root with a ganglion outside the spinal cord and a ventral root with no external ganglion.The dorsal root contains mostly sensory fibres,carrying afferent impulses to the spinal cord.

AUTONOMIC NERVOUS SYSTEM:
The involuntary nervous system which controls and coordinates various function that are carried independently in the body like control rate of heartbeat,the movement of alimentary canal is called autonomic nervous system.It consist of two systems:
1)SYMPATHETIC NERVOUS SYSTEM:
IT is also called thoracic-lumbar outflow because its preganglionic fibres join the spinal cord only in the thoracic and lumbar region.It consists of 2 sympathetic nerves or chains running from the head to the end of sacral regions one on each side of the vertebral column.Preganglionic fibres arise from the spinal cord and pass through ventral roots of spinal nerves.The sympathetic nerves stimulate the adrenal glands to secrete adrenaline.The post ganglionic fibres of sympathetic nerve systems release adrenaline at their nerve endings,so these are called adrenergic nerve fibres.
FUNCTION:
Sympathetic nervous system stimulates increase in heart beat,dilates blood vessels in muscles but constricts peripheral vessels thereby increasing blood pressure,dilates the eyes and increases respiration but slows down the gastro intestinal secretion.
2)PARASYMPATHETIC NERVOUS SYSTEM:
It is also called cranio-sacral out flow because some of the cranial nerves and sacral nerves are involved.It consists of ganglia,preganglionic and post ganglionic fibres.The preganglionic fibres are joined to the cranial nerves of III,VII,IX,X and to the second,third and fourth sacral spinal nerves.So these form CranioSacral Outflow.These form Synapses with neurons of the parasympathetic ganglia.Parasympathetic ganglia are present either near or inside the visceral organs.These are isolated ganglia and are not interlinked to form a chain.
Post ganglionic ganglia are small sized axons of neurons of parasympathetic ganglia and supply smooth muscles and glands or visceral organs.these form a network in the wall of the visceral organs called Aurebach Plexus.Post ganglionic ganglia release acetylcholine in their nerve endings,so these are cholinersic nerve fibres.
FUNCTION:
Sympathetic and parasympathetic nerves supply the same organs but their effects are usually antagonistic(opposite).The parasympathetic stimulation slows down the heart beat,decrease blood pressure ,constricts the pupil of eye and bronchi but speed scretion of gastric tract.These are the opposite functions of sympathetic system.