Peripheral Nervous System 1 and 2

Nerve

A bundle of axons that serve the same function.

Sensory

A type of nerve that carries information from the body to the brain (afferent).

Motor

A type of nerve that carries information from the brain to the body (efferent).

Mixed

A type of nerve that carries both sensory and motor information, and is the most common type.

Spinal Nerves

31 pairs of nerves connected to the spinal cord, numbered by the level of the vertebral column where they emerge from.

Cervical Nerves

Nerves that come out between the skull and C1 vertebrae, and below C7, totaling 8 pairs.

Thoracic Nerves

Nerves numbered T1-T12.

Lumbar Nerves

Nerves numbered L1-L5.

Sacral Nerves

Nerves numbered S1-S5.

Coccygeal Nerve

A pair of nerves that innervate the skin over the coccyx.

Cauda Equina

Nerve roots extending from the end of the spinal cord, forming a "horse's tail" of spinal nerve roots.

Dorsal Root Ganglion

A cluster of sensory neurons with cell bodies in the dorsal root of the spinal nerve.

Ventral Horn

The region of the spinal cord where motor neurons with cell bodies are located.

Dorsal Rami

The branches of spinal nerves that innervate the muscles and skin of the dorsal surface of the head, neck, and trunk.

Ventral Rami

The branches of spinal nerves that innervate the muscles, glands, and skin in ventral extremities, neck, and trunk.

• you have autonomic fibers here (sympathetic rami)

Nerve Plexus

A group of nerves traveling in the same direction, formed from the ventral rami of most spinal nerves.

Cervical Plexus

A plexus formed by the ventral rami of C1-C5, innervating the muscles and skin of the neck, upper shoulders, part of the head, and diaphragm.

Brachial Plexus

A plexus formed by the ventral rami of C5-T1, innervating the lower shoulder and arm.

Lumbar Plexus

A plexus formed by the ventral rami of L1-L4, innervating the abdomen, back, anterior thigh, and leg.

Sacral Plexus

A plexus formed by the ventral rami of L4-S4, innervating the skin of the leg, muscles of the posterior thigh, leg, and foot.

Phrenic Nerves

Nerves originating from the cervical plexus (C3, C4, and C5) that control the diaphragm muscle for respiration.

Dermatome

An area of skin that is supplied by the sensory fibers of a given spinal nerve.

Myotome

A region of skeletal muscles innervated by the motor fibers of a given spinal nerve.

Somatic Nervous System

The division of the peripheral nervous system that is involved with voluntary control of skeletal muscles.

Autonomic Nervous System

The division of the peripheral nervous system that controls automatic functions in the body, such as reflexes and involuntary actions.

Reflex

An involuntary response to a stimulus, involving a reflex arc.

Reflex Arc

The signal conduction route to and from the central nervous system, involving afferent and efferent neurons.

Contralateral

A reflex arc where the sensory receptors and effectors are on opposite sides of the body.

Ipsilateral

A reflex arc where the sensory receptors and effectors are on the same side of the body.

Cranial Nerves

12 pairs of nerves that originate from the brainstem and are identified by name or number.

Olfactory Nerve

The first cranial nerve responsible for the sense of smell.

Optic Nerve

The second cranial nerve responsible for vision.

Oculomotor Nerve

The third cranial nerve responsible for eye movement and regulation of light entering the eye.

Trochlear Nerve

The fourth cranial nerve responsible for controlling the superior oblique muscle of the eye.

Trigeminal Nerve

The fifth cranial nerve that splits into three branches and is responsible for sensory and motor functions of the head and face.

Abducens Nerve

The sixth cranial nerve responsible for controlling the lateral rectus muscle of the eye.

Facial Nerve

The seventh cranial nerve responsible for controlling facial expression and taste sensation.

Vestibulocochlear Nerve

The eighth cranial, sensory function

Vestibular: balance from inner ear

cochlear: hearing from spiral ganglion

Glossopharyngeal Nerve

mixed nerve, sensation for part of toungue and throat, motor for movement of tongue and swallowing

Vagus Nerve

mixed, mainly autonomic, main nerve of parasympathetic, sensory inputs from visceral organs, motor control over those same visceral organs

Accessory Nerve

motor, originates from C1-C5, innervates head and shoulder muscles for movement

hypoglossal nerve

motor only, located under tongue and controls tongue muscles