PERIPHERAL NERVOUS SYSTEM.

The peripheral nervous system includes 31 pairs of spinal nerves, 12 pairs of cranial nerves and the autonomic nervous system.

Each cranial and spinal nerve is covered by the following tissue layers:

1. Endoneurium which is a delicate layer and lies above the individual nerve fiber. Such nerve fibers come together to form fascicles.
2. Perineurium is a layer of smooth connective tissue and each fascicle is wrapped by this layer.
3. Epineurium is the outer layer that surrounds each nerve.

• SPINAL NERVES.

A nerve passing through the spinal cord is called a spinal nerve

There are a total of 31 pairs of spinal nerves that pass through the vertebral column and the nerves passing through are named based on the region that is the vertebra of that region.

This nerve passes from the vertebrae of the vertebral column to the body. Which is named as follows.

Cervical nerve 8 pairs

Parathoracic nerve 12 par

Lumbar nerve 5 pairs

Sacral nerve 5 pairs

Coccygeal nerve 1 pair

The cervical spine passes between the foramen magnum and the first cervical vertebra.

The lower part of the spinal cord is known as the cauda equina or horse tail.

A spinal nerve has anterior and posterior nerve roots in which the posterior nerve root acts as sensory and the anterior nerve root acts as motor.

A mixed nerve is also found in the spinal nerve. Spinal nerves emerge from the vertebrae and join together to form a plexus such plexus is as follows.

Cervical plexus

•Brachial plexus

•Lumbar plexus

•Sacral plexus

•Coccygeal plexus.

The nerves of the thoracic region do not form a plexus.

Branches of nerves from this plexus supply nerves to that area.

•Thoracic nerve..

Does not form a thoracic nerve plexus.

Thoracic nerves are 12 in number

This thoracic nerve passes through the costal groove of the ribs and supplies the intercostal muscles and the skin of that area.

Out of which the first 11 nerves are called costal nerves and Barbi nerve is called sub costal nerve.

• CRANIAL NERVES.

There are 12 pairs of cranial nerves

This cranial nerve is connected with the cranial cavity i.e. brain

This cranial nerve contains sensory, motor and mixed types of nerves.

1. All Factory Nerve..

•This nerve is the sensory nerve that carries the sensation of smell to the brain.

• Receptors are located in the nasal mucosa and the sensation of the smell being stimulated is carried through the olfactory track to the temporal lobe of the brain and the smell is perceived.

1. Optic nerve..

•This is a sensory nerve. The optic nerve takes the sensation of vision from the site i.e. the retina of the eye and passes through the optic foramen and passes through the optic track.

3. Oculo motor nerve..

• It is a motor nerve whose nerve fibers originate from the midbrain

•It also contains autonomic nerve fibers and supplies nine to the intrinsic and extrinsic muscles of the eyeball which enables accommodation of the eye i.e. focusing on any near object and various movements of the eyeball.

4. Trochlear nerve..

It originates from the midbrain and supplies nerves to the superior oblique muscles of the eye.

5. Trigeminal nerve…

•This is a mixed type nerve with three branches

1. Ophthalmic nerve
2. Maxillary nerve
3. Mandibular nerve.

•The nerve fibers of this nerve are connected to the pons veroli and are also connected to the nerve supply to the muscles helping in mastication i.e. chewing.

•6. Abdusant Nerve..

•Its ​​nerve fibers originate from the pons veroli and are connected to the nerve supply to the lateral rectus muscles of the eye.

•7. Facial nerve..

•It originates from the inferior portion of the pons veroli. Nerves supply the muscles of the face, scalp and neck.

• Motor nerve fibers of the facial nerve serve for facial expression.

•Its ​​sensory nerve fibers are attached to the posterior tongue which provides the perception of taste.

8. Vestibulocochlear nerve..

•It is also called auditory nerve. It is a sensory nerve. It has 2 branches.

1. Cochlear nerve. It conveys impulses of hearing. It is attached to the corti of the cochlea, an organ of the inner ear.

2.Vestibular nerve.. It conveys impulses of equilibrium. It is connected to semicircular canal, saccule in inner ear and carries impulses to pons veroli and cerebellum.

9. Glossopharyngeal nerve..

•It is a mixed type of nerve.

• It is associated with the secretion of saliva.
• Its sensory nerve fibers carry test impulses from the tongue to the medulla and act to report the test.
• It also works for the loosening process and gag reflex.

10 Vagus nerve.

•It is a mixed nerve.

• Its sensory nerve fibers supply impulses to pharynx, larynx, trachea, heart, bronchi, esophagus, stomach, small intestine and gall bladder.
• Motor nerve fibers help in the loosening process.

•It is the longest branch of all cranial nerves. and is a major branch of the parasympathetic nervous system.

•11. accessory nerve.

•It is a motor nerve.

•Its ​​nerve fibers originate from the medulla which helps in the dissolving process.

•12. Hypoglossal nerve ..

•It is a motor nerve.

•He is from Medanula.

• Its nerve fibers help in tongue movement during speaking and in the swallowing process.