Nervous System Peripheral Nervous System

Peripheral Nerve System

the peripheral nervous system mainly involves the nerves arising from the central nervous system.
1 cranial nerves : 12 pairs
2 Spinal nerves : 31 pairs

there are mainly two types of nerve fibers sensory and motor . sensory nerve fibre carries impulses from the sense organ to the brain whereas motors nerve fibers carry impulses from the brain to effector organ.

Each nerve is composed of numerous nerve fibres forming bundles with a covering outside the immediate covering of individual nerve fibers is delicate nad called endoneurium A group of nerves fibres are enclosed together, by another common sheath called perineurium. finally, such small bundles of the nerve fibers group together to form nerve and are surrounded by an external common membrane called epineurium.

Cranial Nerve

the nerve originating from the brain called cranial nerves. there are 12 pairs of cranial nerve originated from the lower surface of the brain the cranial nerves are three types sensory motor and mixed the sensory nerve consists of bundles of sensory fibres and the motor nerve consists of bundles of motor nerve fibres the nerve consisting of both sensory and motor nerve fibers are called mixed nerve. the cranial nerve can be named numerically around to their origin from anterior-posterior part of the brain the names and types of the creanial nerve are:-

1 Olfactory nerve

these are also sensory nerves they are concerned with the sense of sight nerve fibers, from the retina of the eyes combines to form the optic nerve and pass into the cranial cavity to join the optic charisma immediately above the pituitary gland these nerve finally pass into the visual area of the cerebrum as the optic tract.

2 Optic nerve

these sensory nerves and are concerned with the sense of sight nerve fibers from the retina of the eyes combine to form the optic nerve and pass into the cranial cavity to join the optic charisma.

3 oculomotor nerve

these nerves are provided with only motor nerve fibers, this nerve arise from the brain and pass tp the effector organs like recti and inferior oblique muscles of the eyes .similarly this nerve also supply ciliary muscles and circular muscles of the iris of the eye.

4 trochlear nerves

these nerves arise from the cerebrum and supply to the superior oblique muscles of the eye.

5 trigeminal nerves

this nerve contains both sensory and motor fiber it consists of three branches the ophthalmic the maxillary and the mandibular first 2 sensory nerves and the laster is the mixed nerve.

6 vesti and Bul cochlear nerves

it nerves pass to the lacrimal gland and conjunctiva of eyes ,this nerve also supplies branches to the forehead eyelids and mucous membrane of the nose. the maxillary nerve supplies the lower jaw lower lip and tongue the motor part of mandibular nerve supply the branches to the muscles of mastication.

7 abudent nerve

these motor nerves arise from the floor of the fourth ventricle they are connected to the lateral rectul muscles of the eye balls.

8 facial nerve

these nerves consist of and arises from the lower parts of pons villi the sensory parts are connected tp taste buds in front of the tongue the motor part of the nerve innervate the skeletal muscles of facia expression and swallowing.

9 glossopharyngeal nerve

these nerves consists of both motor and sensory nerve the sensory nerve ,supply to the taste buds at the back of the tongues and pharynx .the motor nerve arise from the medulla oblongata and innervate the same structure to which sensory part of vagus nerves are connected.

10 Vagus nerves

the vagus nerves arise from the medulla oblongata .the sensory nerves transmit impulses from the different part of the throat and abdomen eg pharynx trachea oesophagus heart stomach, intestine bladder ,pancreas etc brain.

11 Accessory nerves

these nerves arise from the medulla oblongata the nerves innervate neck skeletal muscles.

12 Hypoglossal nerve

these nerves originate from the medulla oblongata they innervate the tongue muscles and the muscles around the hyoid bone.

spinal Nerves

the nerve originating from the spinal cords are called spinal nerve they are 31 pairs in number. they come out from the vertebral canal through intervertebral column forming in between two adjacent vertebrae, these nerves derive their name after the vertebrae to which they are associated therefore there are 4 different kinds of the spinal nerve.
1 cranial
2 thoracic
3 lumbar
4 sacral nerve
5 coccygeal

Reference:

Agrawal, sarita. principle of biology. 2nd edition . kathmandu: Asmita book Publication, 2068 ,2069

Mehta, Krishna Ram. Principle of biology. 2nd edition. kathmandu: Asmita, 2068,2069.

Jorden, S.L. principle of biology. 2nd edition . Kathmandu: Asmita book Publication, 2068.2069.