Nervous part 5

PNS

Consists of nerves and scattered ganglia (groups of neuronal cell bodies found outside the CNS).

Endoneurium

Delicate connective tissue surrounding each nerve fiber.

Perineurium

Coarser connective tissue that wraps groups of nerve fibers and forms fascicles.

Cranial nerves

These nerves primarily serve the head and neck.

Cranial nerve I (Olfactory)

Carries impulses for the sense of smell, its fibers arise from receptors in the nasal mucosa and synapse.

Cranial nerve II (Optic)

Carries impulses for vision, its fibers arise from the retina of the eye.

Cranial nerve III (Oculomotor)

Supplies motor fibers to four of the six eye muscles. Its fibers run from the midbrain to the eye.

Cranial nerve IV (Trochlear)

Supplies motor fibers for one external eye muscle. Fibers run from the midbrain to the eye.

Cranial nerve V (Trigeminal)

Conducts sensory impulses from the skin of the face and mucosa of the nose, mouth, and corneas, but also contains motor fibers that activate chewing muscles. Its fibers emerge from the pons and form three divisions that run to the face.

Cranial nerve VI (Abducens)

Supplies motor fibers to the lateral rectus muscle to roll the eye. Fibers leave the pons and run to the eye.

Cranial nerve VII (Facial)

Activates the muscle of facial expression and the lacrimal and salivary gland, along with carrying sensory impulses from the taste buds of the anterior tongue. Fibers leave the pons and run to the face.

Cranial nerve VIII (Vestibulocochlear)

Has two branches, one for transmitting impulse for hearing and one for sensing balance. It also has a small motor function in adjusting sensitivity of sensory receptors. Fibers run from the equilibrium and hearing receptors.

Cranial nerve IX (Glossopharyngeal)

Fibers emerge from the medulla and run to the throat, it supplies motor fibers to the pharynx that promote swallowing and saliva production. It also carries sensory impulses from taste buds of the posterior tongue.

Cranial nerve X (Vagus)

Fibers emerge from the medulla and descend into the thorax, its fibers carry sensory impulses from and motor impulses to the pharynx, larynx, and the abdominal and thoracic viscera.

Cranial nerve XI (Accessory)

Fibers arise from the superior spinal cord, its fibers activate the sternocleidomastoid and trapezius muscles.

Cranial nerve XII (Hypoglossal)

Fibers run from the medulla to the tongue, and its fibers control tongue movements.

Cervical plexus

Formed by the first four cervical nerves (C1-C4). This supplies the back and sides of the head, and the front of the neck with ordinary sensory fibers. Most important branch is phrenic nerve composed of motor fibers supplying the diaphragm.

Brachial plexus

Lower four cervical (C5-C8) and the first thoracic (T1), it supplies the skin and muscles of the upper limb; with branches like radial, ulnar, median nerves.

Lumbar plexus

From L1-L4; Two of its branches are femoral nerve (supplies muscles and skin on anterior aspect of the thigh) and Obturator nerve (supplies muscles and skin of medial aspect of thigh).

Sacral plexus

From L4-L5 and S1-S3 spinal nerves; The largest branch of which is the sciatic nerve.

Sciatic nerve

The largest nerve in the body, which is divided into common peroneal and tibial nerves.

Sympathetic nervous system

Also called the thoracolumbar division, its nerves arise from the thoracic nerves and the first three nerves of the lumbar region. They generally deal with mobilizing the body energy to deal with increased activity.

Parasympathetic nervous system

Also called the craniosacral division, it arises from the 3rd, 7th, 9th, and 10th cranial nerves as well as the sacral segment of the spinal cord. Its actions generally deal with conserving energy.