acoustic nerve

nerve

[nerv] a macroscopic cordlike structure of the body, comprising a collection of fibers" >nerve fibers that convey impulses between a part of the central nervous system and some other body region. See Appendix 2-6 and see color plates.
Depending on their function, nerves are known as sensory, motor, or mixed. Sensory nerves, sometimes called afferent nerves, carry information from the outside world, such as sensations of heat, cold, and pain, to the brain and spinal cord. Motor nerves, or efferent nerves, transmit impulses from the brain and spinal cord to the muscles. Mixed nerves are composed of both motor and sensory fibers, and transmit messages in both directions at once.
Together, the nerves make up the peripheral nervous system, as distinguished from the central nervous system (brain and spinal cord). There are 12 pairs of cranial nerves, which carry messages to and from the brain. Spinal nerves arise from the spinal cord and pass out between the vertebrae; there are 31 pairs, 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal. The various nerve fibers and cells that make up the autonomic nervous system innervate the glands, heart, blood vessels, and involuntary muscles of the internal organs.

Details of structure of components of nerve tissue.accelerator n's the cardiac sympathetic nerves, which, when stimulated, accelerate the action of the heart.acoustic nerve vestibulocochlear nerve; see anatomic Table of Nerves in the Appendices.afferent nerve any nerve that transmits impulses from the periphery toward the central nervous system, such as a sensory nerve. See also neuron.articular nerve any mixed peripheral nerve that supplies a joint and its associated structures.auditory nerve vestibulocochlear nerve; see anatomic Table of Nerves in the Appendices.autonomic nerve any nerve of the autonomic nervous system" >autonomic nervous system; called also visceral nerve.cranial n's see cranial nerves.cutaneous nerve any mixed peripheral nerve that supplies a region of the skin. See anatomic Table of Nerves in the Appendices.depressor nerve 1. a nerve that lessens the activity of an organ.2. an afferent nerve whose stimulation causes a fall in blood pressure.efferent nerve any nerve that carries impulses from the central nervous system toward the periphery, such as a motor nerve. See also neuron.excitor nerve one that transmits impulses resulting in an increase in functional activity.excitoreflex nerve a visceral nerve that produces reflex action.fusimotor n's those that innervate the intrafusal fibers of the muscle spindle.gangliated nerve any nerve of the sympathetic nervous system.inhibitory nerve one that transmits impulses resulting in a decrease in functional activity.medullated nerve myelinated nerve.mixed nerve (nerve of mixed fibers) a nerve composed of both sensory (afferent) and motor (efferent) fibers.motor nerve a peripheral efferent nerve that stimulates muscle contraction.myelinated nerve one whose axons are encased in a myelin sheath; called also medullated nerve.peripheral nerve any nerve outside the central nervous system.pilomotor n's those that supply the arrector muscles of hair.pressor nerve an afferent nerve whose irritation stimulates a vasomotor center and increases intravascular tension.sciatic nerve see sciatic nerve.secretory nerve an efferent nerve whose stimulation increases vascular activity.sensory nerve a peripheral nerve that conducts impulses from a sense organ to the spinal cord or brain. See also neuron.somatic n's the sensory and motor nerves supplying skeletal muscle and somatic tissues.spinal n's the 31 pairs of nerves arising from the spinal cord and passing out through the vertebrae; there are eight cervical, twelve thoracic, five lumbar, five sacral, and one coccygeal. , and see anatomic Table of Nerves in the Appendices.

Spinal nerves emerging from the spinal cord through the intervertebral foramina with muscles or muscle movements listed for specific levels. From McQuillan et al., 2002.splanchnic n's those of the blood vessels and viscera, especially the visceral branches of the thoracic, abdominal (lumbar), and pelvic parts of the sympathetic trunks. See Appendix 3-5.sudomotor n's those that innervate the sweat glands.sympathetic n's 1. see trunk" >sympathetic trunk.2. any nerve of the sympathetic nervous system.trophic nerve one concerned with regulation of nutrition.unmyelinated nerve one whose axons are not encased in a myelin sheath.vasoconstrictor nerve one whose stimulation causes contraction of blood vessels.vasodilator nerve one whose stimulation causes dilation of blood vessels.vasomotor nerve one concerned in controlling the caliber of vessels, whether as a vasoconstrictor or vasodilator.vasosensory nerve any nerve supplying sensory fibers to the vessels.visceral nerve autonomic nerve.

a·cous·tic nerve

an almost obsolete term still sometimes used incorrectly to designate the vestibulocochlear nerve [CN VIII].

acoustic nerve

n. See vestibulocochlear nerve.

nerve

(nerv) [L. nervus, sinew]

NERVE STRUCTUREParallel axons running together inside a thick connective tissue sheath (an epineurium). In the nerve, axons are wrapped into small bundles by thin connective tissue sheaths (endoneuria); each small bundle of axons is called a fascicle. The neuronal cell bodies of a nerve's axons are in the brain, the spinal cord, or ganglia, but the nerves run only in the peripheral nervous system. Nerves with axons that conduct electrochemical impulses toward the CNS are afferent, nerves with axons that conduct impulses away from the CNS are efferent, and nerves with both afferent and efferent axons are mixed. Nerves in the peripheral nervous system are roughly analogous to tracts in the CNS and, like tracts, act as highways that axons can join or leave on the way from their origin to their target. See: ansa; cell; nervus.; illustration

Symptoms

A broad array of insults may damage nerves, including direct trauma, repetitive motion injuries, compression by neighboring structures, glycosylation, infections, drugs, toxins, and paraneoplastic syndromes. Symptoms of nerve injury include paresthesias, loss of sensation and position sense, impaired motor function, cranial nerve malfunction, changes in reflexes, and impairments in glandular secretion.

Tests for Loss of Function

The assessment of nerve injury includes a careful neurological examination, sometimes accompanied by tests, e.g., electromyography or nerve conduction studies.

abducens nerve

A somatic motor nerve originating in the abducens nucleus in the pons. It runs in the subarachnoid space and the cavernous sinus inside the skull, enters the back of the orbit through the superior orbital fissure, and innervates the lateral rectus muscle. Synonym: abducent nerve; sixth cranial nerve See: cranial nerve

abducent nerve

Abducens nerve.

accelerator nerve

A sympathetic nerve to the heart that carries impulses that speed the heart rate.

accessory nerve

Spinal accessory nerve. See: cranial nerve for illus.

ACOUSTIC NERVE (8th CRANIAL)

acoustic nerve

Auditory nerve. See: illustration

adrenergic nerve

A nerve that uses a catecholamine as its main neurotransmitter.

afferent nerve

A nerve that conducts impulses toward the brain or spinal cord. See: sensory nerve

alveolar nerve

Any of the sensory nerves to the teeth; they are branches of the trigeminal nerve (CN V). The superior alveolar nerves innervate the upper teeth and gingivae; the inferior alveolar nerves innervate the lower teeth and gingivae. The anterior superior alveolar nerves, branches of the infraorbital nerve (from CN V2), run in canals in the anterior wall of the maxillary sinus and innervate the upper incisors, canines, premolars, and often part of the first molar. Sometimes there is a middle superior alveolar nerve that innervates the premolars and first molar. The posterior superior alveolar nerves (also from CN V2) innervate the rest of the upper molars. The inferior alveolar nerve (from CN V3) runs in the mandibular canal, giving off branches to the lower teeth and gingivae as it passes. Synonym: dental nerve

antebrachial cutaneous nerve

See: lateral antebrachial cutaneous nerve; medial antebrachial cutaneous nerve; posterior antebrachial cutaneous nerve

auditory nerve

The component of the vestibulocochlear nerve (CN VIII) that carries axons conveying sound information between the spiral ganglion in the inner ear and the cochlear nuclei in the brainstem. Synonym: acoustic nerve; cochlear nerve

auricular nerve

Any of three nerves, the great auricular nerve, the posterior auricular nerve, or the auricular branch of the vagus nerve (CN X). The great auricular nerve is a sensory branch of the cervical plexus composed of axons from spinal cord segments C2–C3; it innervates the skin and fascia behind the ear, on the lower part of the pinna of the ear, and over the angle of the jaw. The posterior auricular nerve is a motor branch of the facial nerve (CN VII) that innervates the posterior and intrinsic auricular muscles. The auricular branch of the vagus nerve is a sensory nerve emerging from the superior ganglion of the vagus nerve, joined by branches from the glossopharyngeal (CN IX) and facial nerves, and innervating the lower part of the tympanic membrane and the floor of the external auditory canal.

auriculotemporal nerve

A sensory branch of the mandibular nerve (CN V3) It passes through the parotid gland en route to the ear, where it innervates skin of the pinna, external auditory canal, and tympanic membrane.

autonomic nerve

A visceral motor (visceral efferent) nerve, innervating smooth muscle, cardiac muscle, or glands. Visceral motor nerves can contain pre- or postganglionic sympathetic or parasympathetic axons. Visceral sensory (visceral afferent) axons can run in autonomic or somatic nerves.

axillary nerve

A mixed nerve of the posterior upper arm originating in the posterior cord of the brachial plexus and composed of axons from spinal cord segments C5-C6.

Sensory

It innervates skin over the shoulder joint and the lower portion of the deltoid muscle.

Motor

It innervates the teres minor and deltoid muscles.

brachial cutaneous nerve

See: lateral brachial cutaneous nerve; medial brachial cutaneous nerve; posterior brachial cutaneous nerve

buccal nerve

1. A branch of the mandibular nerve (CN V3).

Sensory

It innervates skin over the lower cheek, mucous membranes inside the cheek, and the buccal gingivae along the second and third lower molar.

Motor

It innervates the lateral pterygoid muscle.

2. A motor branch of the facial nerve (CN VII) that innervates the buccinator and neighboring facial muscles.

calcaneal nerve

Any of the nerves that are sensory branches of the tibial nerve and innervate the skin on the heel and the medial side of the sole of the foot.

cardiac nerve

Any of the autonomic nerves traveling to the cardiac plexus. The three main sympathetic nerves (superior cardiac nerve, middle cardiac nerve, and inferior cardiac nerve) originate in the superior, middle, and inferior cervical sympathetic ganglia. The preganglionic parasympathetic innervation of the cardiac plexus is from the vagus nerve (CN X).

carotid nerve

1. Any of the nerves from the superior cervical ganglion of the sympathetic trunk that form plexuses around the carotid arteries. The internal carotid nerves form a plexus around the internal carotid artery inside the carotid canal; the external carotid nerves form a plexus around the external carotid artery. 2. Carotid sinus nerve.

carotid sinus nerve

A sensory branch of the glossopharyngeal nerve (CN IX) carrying signals from the baroceptors (blood pressure receptors) in the bifurcation of the carotid artery to the nucleus of the solitary tract (nucleus solitarius). Synonym: carotid nerve

cervical nerve

1. Any of the eight pairs of spinal nerves that originate in the cervical segments of the spinal cord. They are abbreviated C1 to C8. The first cervical spinal nerve (C1) emerges from the spinal canal above the first cervical vertebra; the eighth cervical spinal nerve (C8) emerges from between the seventh cervical vertebra and the first thoracic vertebra. Cervical spinal nerves innervate the neck, shoulders, and arms. 2. A motor branch of the facial nerve (CN VII) that emerges from the lower end of the parotid gland and runs down behind the angle of the jaw to innervate the platysmus muscle.

cholinergic nerve

A nerve that uses acetylcholine as its main neurotransmitter.

ciliary nerve

Either of two nerves, the long ciliary nerve and the short ciliary nerve, that carry sensory axons and postganglionic sympathetic fibers that innervate the ciliary body, iris, and cornea of the eye. The long ciliary nerves are branches of the nasociliary nerve; the short ciliary nerves come from the ciliary ganglion and also contain preganglionic parasympathetic axons.

coccygeal nerve

The tiny final nerve of the spinal cord, which is composed of axons from spinal nerves S4–S5; it innervates the coccygeus and levator ani muscles and the skin over the coccyx.

cochlear nerve

Auditory nerve.

collateral nerve

An offshoot nerve composed of branches of some of the axons in the main nerve.

common fibular nerve

Common peroneal nerve.

common peroneal nerve

One of the two divisions of the sciatic nerve in the leg. The sciatic nerve branches into the tibial and common peroneal nerves in the apex of the popliteal fossa. The common peroneal nerve winds around the proximal neck of the fibula to reach the anterior leg where it divides into the superficial and deep peroneal nerves. The common peroneal nerve innervates the knee joint and the skin of the lateral side of the upper leg. Synonym: common fibular nerve

CRANIAL NERVES AND THEIR DISTRIBUTIONS

cranial nerve

Abbreviation: CN
Any of the twelve pairs of nerves that leave the cranial cavity through foramina in the skull and innervate the head. The cranial nerves are numbered in the order they contact the brain; from anterior to posterior, they are the olfactory (CN I), optic (CN II), oculomotor (CN III), trochlear (CN IV), trigeminal (CN V), abducens (CN VI), facial (CN VII), vestibulocochlear (CN VIII), glossopharyngeal (CN IX), vagus (CN X), spinal accessory (CN XI), and hypoglossal (CN XII) nerves. The central nuclei for all the cranial nerves, except the olfactory nerve, are in the brainstem. See: illustration

Diagnosis

Lesions of the cranial nerves give rise to the following alteration(s): First (CN I; olfactory): Loss of the sense of smell. Second (CN II; optic): Blindness in all or part of a visual field. Third (CN III; oculomotor): Ptosis (drooping) of the eyelid, deviation of the eyeball outward, immobility of the pupil, double vision. Fourth (CN IV; trochlear): Rotation of the eyeball upward and outward, double vision. Fifth (CN V; trigeminal):

Sensory

Pain or loss of sensation in the face

Motor

Weakness of the jaw, difficulty chewing. Sixth (CN VI; abducens): Deviation of the eye outward, double vision. Seventh (CN VII; facial): Paralysis of muscles of facial expression. Eighth (CN VIII; vestibulocochlear): Deafness; ringing in the ears; dizziness; nausea and vomiting; reeling. Ninth (CN IX; glossopharyngeal): Disturbance of taste; difficulty in swallowing; loss of gag reflex. Tenth (CN X; vagus): hoarseness; difficulty swallowing; autonomic disturbances of the viscera.Eleventh (CN XI; spinal accessory): Drooping of the shoulder; inability to rotate the head. Twelfth (CN XII; hypoglossal): Paralysis of the tongue, deviation of the tongue toward one side; thick speech.

cutaneous nerve

A nerve that mainly provides sensory innervation to the skin.

deep fibular nerve

Deep peroneal nerve.

deep peroneal nerve

One of the two major branches of the common peroneal nerve formed as the latter winds around the proximal neck of the fibula. The deep peroneal nerve runs along the interosseous membrane (between the fibula and tibia) into the dorsal foot. It innervates anterior leg muscles and the skin of the dorsal surface of the foot. Synonym: deep fibular nerve

deep petrosal nerve

A bundle of postganglionic sympathetic axons from the superior cervical ganglion. These axons take the internal carotid nerve into the carotid canal in the skull, where they form the internal carotid plexus. From this plexus, the axons emerge as the deep petrosal nerve, which then joins the greater petrosal nerve in the vidian canal, en route to the pterygopalatine ganglion.

deep temporal nerve

Temporal nerve (1).

dental nerve

Alveolar nerve.

depressor nerve

Any nerve whose stimulation depresses the activity of an organ or nerve center.

digital nerve

Any of the branches of the median nerve that arise near the flexor retinaculum and innervate lumbricals, joints, and the palmar skin of the fingers.

dorsal nerve

Posterior ramus.

dorsal nerve of the clitoris

A branch of the pudendal nerve that transmits sensory information from the clitoris. The autonomic innervation of the clitoris comes from the inferior hypogastric plexus.

dorsal nerve of the penis

A branch of the pudendal nerve that transmits sensory information from the penis. The autonomic innervation of the penis comes from the inferior hypogastric plexus.

dorsal scapularnerve

A branch of spinal nerve C5, which runs in the posterior shoulder and innervates the rhomboid muscles.

efferent nerve

A nerve conducting impulses away from the brain or spinal cord. Synonym: motor nerve

eighth cranial nerve

Abbreviation: CN VIII
Acoustic nerve.

eleventh cranial nerve

Abbreviation: CN XI
Spinal accessory nerve.

ethmoidal nerve

Either of two nerves, the anterior ethmoidal nerve or the posterior ethmoidal nerve, that are sensory branches of the nasociliary nerve.

excitatory nerve

A nerve that heightens, increases, or starts the activity of its target.

excitoreflex nerve

A visceral nerve whose stimulation causes reflex action.

SUPERFICIAL BRANCHES OF FACIAL NERVE (7TH CRANIAL))

facial nerve

A mixed nerve consisting of efferent fibers supplying the facial muscles, the platysma muscle, the submandibular and sublingual glands; and of afferent fibers from taste buds of the anterior two thirds of the tongue and from the muscles.

Sensory

Taste fibers from the anterior two thirds of the tongue and the soft palate follow the chorda tympani to their neuronal cell bodies in the geniculate ganglion; the axons of these neurons follow the nervus intermedius (the sensory root of the facial nerve) into the pons where they synapse in the nucleus of the tractus solitarius (the gustatory nucleus).

Motor

Somatic motor axons from the motor nucleus of the facial nerve in the pons emerge as the motor root of the facial nerve and enter the bone of the skull through the internal auditory meatus. The motor axons follow the facial canal inside the temporal bone and exit the skull through the stylomastoid foramen. From there, the axons innervate all the muscles of facial expression. Preganglionic parasympathetic axons from the superior salivatory nucleus take the nervus intermedius to the region of the geniculate ganglion inside the facial canal. From there, some of the axons join the chorda tympani and later reach the submandibular ganglion by following the lingual nerve. Other preganglionic parasympathetic axons follow the major superficial petrosal nerve and the vidian nerve to reach the pterygopalatine ganglion.

Synonym: seventh cranial nerve See: illustration; cranial nerve

femoral nerve

1. A mixed nerve originating in the lumbar plexus and composed of axons from spinal cord segments L2–L4. It runs into the thigh, passing under the inguinal ligament, on the lateral side of the femoral vessels. It then divides into a number of branches, including the anterior cutaneous nerves of the thigh and the saphenous nerve.

Sensory

The femoral nerve and its branches innervate the skin along the distal anterior thigh, the front and medial side of the knee, and the medial leg and foot. They also innervate the hip and knee joints.

Motor

The femoral nerve and its branches innervate the pectineus, sartorius, and quadriceps muscles.

2. A sensory branch of the genitofemoral nerve that runs in the femoral sheath and innervates skin over the femoral triangle.

fifth cranial nerve

Abbreviation: CN V
Trigeminal nerve.

first cranial nerve

Abbreviation: CN I
Olfactory nerve.

fourth cranial nerve

Abbreviation: CN IV
Trochlear nerve.

frontal nerve

A sensory branch of the ophthalmic nerve (CN V1). It runs in the orbit above the eye where it branches into the supraorbital and supratrochlear nerves. The frontal nerve innervates the conjunctiva lining the upper eyelid; the mucosa of the frontal sinus; and the skin of the upper eyelids, forehead, and front half of the scalp.

GABAergic nerve

A nerve that uses gamma-aminobutyric acid (GABA ) as its main neurotransmitter.

gangliated nerve

Any nerve of the sympathetic nervous system.

gastric nerve

Any of the autonomic nerves to the stomach from the esophageal plexus that are composed of axons from the vagus (CN X) and greater splanchnic nerves.

genital nerve

A sensory branch of the genitofemoral nerve that enters the inguinal canal through the internal ring and innervates the cremaster muscles and scrotal skin in males and the skin of the mons pubis and the labium majus in females.

genitofemoral nerve

A sensory nerve originating in the lumbar plexus and composed of axons from spinal cord segments L2–L3. It runs along the surface of the psoas major muscle where it divides into a genital branch and a femoral branch; the branches innervate the skin of the scrotum or labium and the skin over the femoral triangle.

GLOSSOPHARYNGEAL NERVE

glossopharyngeal nerve

A mixed nerve that is sensory for taste and for the carotid sinus and body, and motor for secretion of saliva and contraction of the pharynx.

Sensory

Taste fibers from the posterior third of the tongue join visceral sensory fibers from the pharynx, auditory tube, middle ear, carotid sinus, and carotid body and run back to their neuronal cell bodies in the superior and inferior ganglia of the glossopharyngeal nerve, located in the jugular foramen. The axons of these ganglionic neurons follow the glossopharyngeal roots into the hindbrain where they synapse in the nucleus of the tractus solitarius and the spinal nucleus of the trigeminal nerve.

Motor

The glossopharyngeal nerve emerges from the medulla as a line of small rootlets just anterior to the rootlets of the vagus nerve (CN X). The glossopharyngeal rootlets collect into a single nerve that emerges from the skull through the jugular foramen, along with the vagus and spinal accessory (CN XI) nerves. The glossopharyngeal nerve then divides into branches as it runs along the stylopharyngeus muscle.

Course

CN IX.

Synonym: ninth cranial nerve See: illustration

greater occipital nerve

A prominent sensory component of the dorsal ramus of spinal nerve C2. It leaves the spinal canal between the first and second vertebrae and runs up the back of the neck to innervate the skin over the occipital bone of the skull. Synonym: occipital nerve

greater petrosal nerve

A sensory and autonomic branch of the facial nerve (CN VII) that carries taste axons from the palate and preganglionic parasympathetic axons destined for the pterygopalatine ganglion. The greater petrosal nerve leaves the facial nerve in the facial canal near the geniculate ganglion; it runs forward in the greater petrosal groove on the surface of the petrous portion of the temporal bone, enters the forward edge of the foramen lacerum, and merges with the deep petrosal nerve to form the vidian nerve. Synonym: greater superficial petrosal nerve; major superficial petrosal nerve

greater superficial petrosal nerve

Greater petrosal nerve.

hepatic nerve

Any of the branches of the gastric nerves that supply autonomic innervation of the liver and biliary system.

hypoglossal nerve

A somatic motor nerve originating in the hypoglossal nucleus of the hindbrain. The nerve collects from a short line of rootlets and exits the skull through the hypoglossal canal. It then innervates the intrinsic muscles of the tongue (the superior and inferior longitudinal, transverse, and vertical muscles) and three of the extrinsic muscles of the tongue (the styloglossus, hyoglossus, and genioglossus muscles). Synonym: twelfth cranial nerve

iliohypogastric nerve

A sensory nerve originating in the lumbar plexus and composed of axons from spinal cord segment L1. It runs parallel to the iliac crest and innervates the skin in a band from the upper lateral side of the buttock to the abdomen above the pubis.

ilioinguinal nerve

A sensory nerve originating in the lumbar plexus and composed of axons from spinal cord segment L1. It runs with the spermatic cord (in males) or the round ligament (in females) through the internal inguinal ring to the skin of the scrotum or labium majus. It innervates the skin of the proximal and medial thigh and of the scrotum or labium majus.

inferior gluteal nerve

A mixed nerve of axons from spinal nerves L5–S2. It follows the sciatic nerve out of the pelvis, and it innervates the gluteus maximus muscle.

inferior rectal nerve

A mixed nerve that is a branch of the pudendal nerve. It follows the inferior rectal vessels to innervate the external anal sphincter, the walls of the lower anal canal, and the perineal skin around the anus.

infraorbital nerve

The terminal branch of the maxillary nerve (CN V2). It is a sensory nerve that leaves the floor of the orbit through the infraorbital foramen and innervates the upper incisors and canine teeth, the mucosa of the maxillary sinus, and the skin of the lower eyelid, cheek, side of the nose, and upper lip.

infratrochlear nerve

A sensory branch of the nasociliary nerve. It runs along the medial wall of the orbit and innervates the skin and lining of the upper eyelid.

inhibitory nerve

A nerve that dampens, decreases, or stops the activity of its target.

intercostal nerve

Any of the eleven pairs of parallel nerves originating in the ventral rami of thoracic spinal nerves T1–T11. Each intercostal nerve runs forward, with a companion intercostal artery and vein, along the lower inner edge of its corresponding rib. It innervates the intercostal muscles and overlying skin.

intermediate nerve

Nervus intermedius.

lacrimal nerve

A small sensory branch of the ophthalmic nerve (CN V2). It runs along the top of the lateral rectus muscle in the orbit and innervates the lacrimal gland and the overlying conjunctiva and skin.

laryngeal nerve

Any of the sympathetic nerves from the superior cervical ganglion that join the superior laryngeal nerve to innervate the larynx and epiglottis.

lateral antebrachial cutaneous nerve

A sensory nerve that innervates the skin along the entire lateral surface of the forearm. It is the terminal branch of the musculocutaneous nerve. Synonym: lateral cutaneous nerve of the forearm

lateral brachial cutaneous nerve

A sensory branch of the axillary nerve that innervates the skin over the lateral lower edge of the deltoid muscle. Synonym: lateral cutaneous nerve of the arm

lateral cutaneous nerve of the arm

Lateral brachial cutaneous nerve.

lateral cutaneous nerve of the forearm

Lateral antebrachial cutaneous nerve.

lateral femoral cutaneous nerve

A sensory nerve that originates from the lumbar plexus and is composed of axons from spinal cord segments L2–L3. It runs into the lower limb by passing under the inguinal ligament, and it innervates skin on the anterior and lateral surfaces of the thigh.

lateral pectoral nerve

A motor nerve originating in the lateral cord of the brachial plexus and composed of axons from C5–C7. It innervates the pectoralis major and pectoralis minor muscles.

lateral plantar nerve

A mixed nerve that is a terminal branch of the tibial nerve; it angles laterally from the medial plantar nerve along the sole of the foot.

Sensory

It innervates the skin on the lateral one-third of the sole and on the plantar side of the last 1 1/2 toes.

Motor

It innervates the quadratus plantae, abductor digiti minimi, flexor digiti minimi brevis, plantar and dorsal interossei, lateral three lumbricals, and adductor hallucis muscles.

lesser occipital nerve

A sensory nerve composed of axons from spinal cord segments C2–C3. It innervates the skin over the back of the neck.

lingual nerve

A sensory branch of the mandibular trunk (CN V3). It is joined by the chorda tympani before entering the lateral floor of the mouth. The lingual nerve then runs toward the front of the mandible, between the hyoglossus and mylohyoid muscles, and ends near the front of the base of the tongue. It innervates the submandibular ganglion, the mucosa along the base of the mouth, the anterior two-thirds of the tongue, and the inner lower gingivae.

long thoracic nerve

A motor nerve composed of axons from spinal nerves C5–C7. It runs down along the lateral chest wall and innervates the serratus anterior muscle.

lumbar nerve

Any of the five pairs of spinal nerves originating in the lumbar segments of the spinal cord. Each lumbar spinal nerve emerges from the spinal canal through the intervertebral foramen below its corresponding vertebra. Lumbar spinal nerves innervate the lower limbs.

lumbar splanchnic nerve

Bundles of sympathetic axons from the lumbar ganglia of the sympathetic trunk that run to the inferior mesenteric and hypogastric plexuses.

major superficial petrosal nerve

Greater petrosal nerve.

mandibular nerve

Abbreviation: CN V3
1. The inferior trunk of the trigeminal cranial nerve. The mandibular nerve is both sensory and motor.

Sensory

The major sensory branches are the auriculotemporal, lingual, and inferior alveolar nerves, which innervate the lower teeth and gingivae and the skin of the lower lip, chin, and jaw up into the "sideburn area" in front of the ear.

Motor

The major motor branches are the lateral pterygoid, masseteric, deep temporal, and buccal nerves, which innervate the muscles of mastication (lateral and medial pterygoids, masseter, and temporalis).

Course

The mandibular nerve leaves the skull via the foramen ovale.

2. A motor branch of the facial nerve (CN VII) that innervates the facial muscles of the lower lip and chin.

masseteric nerve

A motor branch of the mandibular nerve (CN V3) that innervates the masseter muscle and the temporomandibular joint.

maxillary nerve

Abbreviation: CN V2
The middle trunk of the trigeminal cranial nerve. The maxillary nerve is purely sensory; its major branches are the pterygopalatine, posterior superior alveolar, zygomatic, and infraorbital nerves, which innervate the palate, nasal cavity, upper teeth, and the skin of the lower eyelids, checks, nose, and upper lip. COURSE: The maxillary nerve leaves the skull, and enters the pterygopalatine fossa, via the foramen rotundum.

medial antebrachial cutaneousnerve

A sensory nerve originating in the medial cord of the brachial plexus and composed of axons from spinal cord segments C8–T1, which innervates skin on the medial side of the forearm. Synonym: medial cutaneous nerve of the forearm

medial brachial cutaneous nerve

A sensory nerve originating in the medial cord of the brachial plexus and composed of axons from spinal cord segments C8–T1. It innervates skin on the medial side of the arm. Synonym: medial cutaneous nerve of the arm

medial cutaneous nerve of the arm

Medial brachial cutaneous nerve.

medial cutaneous nerve of the forearm

Medial antebrachial cutaneous nerve.

medial pectoral nerve

A motor nerve originating in the medial cord of the brachial plexus and composed of axons C8–T1. It innervates the pectoralis minor muscle and a portion of the pectoralis major muscle.

medial plantar nerve

A mixed nerve that is a terminal branch of the tibial nerve and that runs along the sole of the foot.

Sensory

It innervates the skin on the medial two-thirds of the sole and the plantar side of the first 3 1/2 toes.

Motor

It innervates the abductor hallucis, flexor digitorum brevis, flexor hallucis brevis, and first lumbrical muscles.

median nerve

A mixed nerve of the upper limb originating in the lateral and medial cords of the brachial plexus and composed of axons from spinal cord segments C6–T1.

Sensory

It innervates the skin of the first 3 1/2 digits and the palm proximal to them.

Motor

In the forearm, it innervates the flexor carpi radialis, palmaris longus, pronator teres, flexor digitorum profundus, flexor digitorum superficialis, flexor pollicis longus, and pronator quadratus. In the hand, it innervates the thenar muscles (other than the adductor pollicis and the deep head of the flexor pollicis brevis) and the lumbricals of digits 2 and 3.

Course

It runs in the anterior forearm, roughly midway between the radial and ulnar arteries; it becomes superficial near the wrist and then runs inside the carpal tunnel.

mental nerve

A sensory nerve, the terminal branch of the inferior alveolar nerve. It runs in the mandibular canal, emerges through the mental foramen, and innervates the mucosa of the lower lip and the skin of the lower lip and chin.

mixed nerve

A nerve containing both afferent (sensory) and efferent (motor) axons.

motor nerve

A nerve conveying efferent information to an effector target, such as a muscle or a gland. Synonym: efferent nerve

musculocutaneous nerve

A mixed nerve of the upper limb originating in the lateral cord of the brachial plexus and composed of axons from spinal cord segments C5–C7.

Sensory

Distal to the elbow, it becomes the lateral antebrachial cutaneous nerve, which innervates the skin and fascia of the lateral half of the forearm.

Motor

It innervates the coracobrachialis, biceps brachii, and brachialis muscles.

Course

It runs between the biceps brachii and brachialis muscles.

myelinated nerve

A nerve containing axons wrapped in myelin. Myelinated axons transmit signals more rapidly than unmyelinated fibers.

mylohyoid nerve

A motor branch of the inferior alveolar nerve that arises just proximal to the mandibular foramen. It innervates the mylohyoid muscle and the anterior belly of the digastric muscle.

nasal nerve

Any of the medial, lateral, and external nasal nerves that are sensory branches of the nasociliary nerve. They enter the top of the nasal cavities and innervate the internal walls of the nose.

nasociliary nerve

A sensory branch of the ophthalmic nerve (CN V1). It passes over the top of the optic nerve in the orbit. Its branches include the anterior and posterior ethmoidal, medial, lateral, and external nasal, and infratrochlear nerves. It innervates the upper nasal cavity, the conjunctiva of the upper eyelid, and skin along the nose and upper eyelid.

nasopalatine nerve

A sensory and autonomic nerve that runs from the pterygopalatine ganglion through the adjacent sphenopalatine foramen into the roof of the posterior nasal cavity. Its branches innervate the roof, septum, and floor of the nasal cavity and, via the incisive canal, the hard palate and the gingivae behind the upper incisors.

ninth cranial nerve

Abbreviation: CN IX
Glossopharyngeal nerve

noradrenergic nerve

A nerve that uses norepinephrine as its main neurotransmitter.

obturator nerve

A motor nerve originating in the lumbar plexus and composed of axons from spinal cord segments L2–L4. It passes into the thigh through the obturator foramen of the pelvic bones and innervates the adductor longus, adductor brevis, gracilis, pectineus, obturator externus, and adductor magnus muscles.

occipital nerve

Greater occipital nerve.

oculomotor nerve

A somatic and visceral motor nerve originating in the midbrain oculomotor nucleus and the adjacent Edinger-Westphal nucleus. The oculomotor nerve runs in the subarachnoid space and cavernous sinus inside the skull and enters the orbit through the superior orbital fissure. Its somatic motor axons innervate the superior, medial, and inferior rectus muscles, the inferior oblique muscle, and the superior levator palpebrae muscle. Its preganglionic parasympathetic axons synapse in the ciliary ganglion; the ganglion cell axons (postganglionic parasympathetic axons) follow the short ciliary nerves into the eyeball to innervate the ciliary muscle of the lens of the eye and the pupillary constrictor muscles. Synonym: third cranial nerve

RIGHT OLFACTORY NERVE

olfactory nerve

A sensory nerve with neuronal cell bodies located in the olfactory epithelium (a yellowish-brown thickened patch of epithelium found along the upper back walls of the nasal cavity). Axons from the receptor cells join into approximately 20 small nonmyelinated bundles (the olfactory nerves). These nerves pass into the skull through holes in the cribriform plate of the ethmoid bone and terminate in the ipsilateral olfactory bulb in spherical synaptic structures called glomeruli. Synonym: first cranial nerve See: cranial nerveillustration

ophthalmic nerve

Abbreviation: CN V1
The superior trunk of the trigeminal cranial nerve. The ophthalmic nerve is purely sensory; its major branches are the nasociliary, frontal, and lacrimal nerves, which innervate the eyeball, upper part of the nasal cavity, and the skin of the upper eyelids, forehead, and front half of the scalp. COURSE: The ophthalmic nerve leaves the skull and enters the orbit through the superior orbital fissure.

optic nerve

A sensory nerve composed of the axons of the retinal ganglion cells in the eye. The nerve runs from the back of the eye, through the optic canal, and into the middle cranial fossa. In front of the stalk of the pituitary gland, the right and left optic nerves merge to form the optic chiasm. Here axons from the nasal portion of each retina cross to the other side and join the axons from the contralateral temporal retina to run as the optic tract, which synapses in the lateral geniculate bodies (nuclei) of the thalamus and the superior colliculus of the tectum of the midbrain. In the optic nerve, which runs from the eyeball to the optic chiasm, the full visual information from one eye is transmitted; in the optic tract, which runs from the optic chiasm to the thalamus and midbrain, the full visual information from one visual field is transmitted. Synonym: second cranial nerve

palatine nerve

Either of two nerves, the greater palatine nerve and the lesser palatine nerve, that leave the pterygopalatine ganglion and run down the greater palatine canal, giving rise to branches that innervate the nasal mucosa. At the bottom of the canal, the nerves branch to innervate the roof of the mouth, soft palate, and tonsil.

pancreatic nerve

Any of the autonomic nerves innervating the pancreas from the vagus nerve (CN X) and the splanchnic nerves (from spinal cord segments T5–T9).

parasympathetic nerve

A nerve composed of axons of the parasympathetic division of the autonomic nervous system. Parasympathetic innervation is always a chain of two consecutive axons. The first axon, the preganglionic parasympathetic axon, has its cell body in the brainstem or in the intermediate gray column of spinal cord segments S2–S4; the first axon leaves the brainstem through the oculomotor (CN III), facial (CN VII), glossopharyngeal (CN IX), or vagus (CN X) nerve, or it leaves the sacral spinal cord through a pelvic splanchnic nerve. The second axon in the chain, the postganglionic parasympathetic axon, has its cell body in a peripheral ganglion near its target tissue. The main transmitter used by both pre- and postganglionic parasympathetic axons is acetylcholine. In general, stimulation of parasympathetic nerves relaxes the body tone.

pectoral nerve

See: lateral pectoral nerve; medial pectoral nerve

pelvic splanchnic nerve

Parasympathetic axons from spinal cord segments S2–S4 that are en route to the inferior hypogastric plexus.

peptidergic nerve

A nerve that uses a peptide, e.g., substance P, as its main neurotransmitter.

perineal nerve

A branch of the pudendal nerve. It innervates the skin of the scrotum or labium majus, perineum, and medial thigh and the muscles and mucous membranes of the genital erectile tissues.

peripheral nerve

A nerve outside the central nervous system (CNS).

perivascular nerve

Any of the utonomic nerves surrounding and innervating blood vessels. Synonym: perivascular nerve plexus

pharyngeal nerve

1. An autonomic nerve from the pterygopalatine ganglion that innervates the mucosa of the nasopharynx. 2. A sympathetic nerve from the superior cervical ganglia that innervates the pharynx and its surrounding pharyngeal plexus.

phrenic nerve

A mixed nerve composed of axons from spinal nerves C3 –C5. It descends through the neck behind the carotid sheath; in the chest, it lies between the mediastinal pleura and the pericardium. It is sensory and motor to the diaphragm and sensory to the pericardium.

pilomotor nerve

A motor nerve that innervates the arrectores pilorum muscles of hair follicles.

posterior antebrachial cutaneous nerve

A sensory branch of the radial nerve that innervates a strip of skin along the posterior surface (back) of the forearm. Synonym: posterior cutaneous nerve of the forearm

posterior brachial cutaneous nerve

A sensory branch of the radial nerve that originates in the arm and that innervates a patch of skin along the posterior surface of the arm. Synonym: posterior cutaneous nerve of the arm

posterior cutaneous nerve of the arm

Posterior brachial cutaneous nerve.

posterior cutaneous nerve of the forearm

Posterior antebrachial cutaneous nerve.

posterior cutaneous nerve of the thigh

Posterior femoral cutaneous nerve.

posterior femoral cutaneous nerve

A sensory nerve originating in the sacral plexus and composed of axons from spinal cord segments S1–S3. It innervates the skin of the lateral perineum, buttock, upper medial and posterior thigh, and calf. Synonym: posterior cutaneous nerve of the thigh

presacral nerve

Superior hypogastric plexus.

nerve of the pterygoid canal

Vidian nerve.

pressor nerve

An afferent nerve whose stimulation excites the vasoconstrictor center, thus increasing the blood pressure.

pudendal nerve

A mixed nerve composed of axons from spinal nerves S2–S4. It follows the sciatic nerve out of the pelvis but immediately reenters through the lesser sciatic foramen. It innervates most of the structures of the perineum: it is sensory to the genitals and motor to the perineal muscles, the external urethral sphincter, and the external anal sphincter.

pulmonary nerve

Any of the sympathetic and parasympathetic nerves from the pulmonary plexus that innervate the bronchial muscles, glands, mucous membranes, and alveoli.

purinergic nerve

A nerve with axons that secrete adenosine triphosphate (ATP) or other purine nucleotides as a neurotransmitter or as a local chemical modulator.

radial nerve

A mixed nerve of the upper limb, the continuation of the posterior cord of the brachial plexus and composed of axons from spinal cord segments C5–T1.

Sensory

The radial nerve innervates skin along the lateral posterior arm via the posterior and lower lateral brachial cutaneous nerves. The radial nerve also innervates a strip of skin along the posterior forearm via the posterior antebrachial cutaneous nerve and the skin on the lateral half of the dorsal surface of the wrist, hand, and first 2 1/2 digits via the superficial branch of the radial nerve.

Motor

The radial nerve innervates the triceps brachii, brachialis, brachioradialis, extensor carpi radialis longus, and anconeus muscles. The deep branch of the radial nerve innervates the abductor pollicis longus, extensor carpi radialis brevis, extensor pollicis brevis, supinator, extensor carpi ulnaris, extensor digitorum, extensor indicis, extensor pollicis longus, extensor digiti minimii, and abductor digiti minimi muscles.

Course

From the posterior cord of the brachial plexus, the radial nerve runs with the deep brachial artery along the back of the humerus; it comes laterally around the humerus and continues distally, passing over the lateral condyle of the humerus. There it divides into the superficial and deep branches of the radial nerve, which continue into the forearm.

recurrent laryngealnerve

A branch of the vagus nerve (CN X). It leaves the vagus in the root of the neck: on the right, it loops under the subclavian artery, while on the left it loops under the arch of the aorta. It then ascends along the lateral wall of the trachea to the larynx where it innervates all the intrinsic muscles except the cricothyroid muscle; it is also sensory to the mucosa below the vocal folds. Injuries of the recurrent laryngeal nerve cause hoarseness, dysphagia, and dyspnea.

recurrent meningeal nerve

Sinuvertebral nerve.

renal nerve

The lowest (least) splanchnic nerve, which carries sympathetic axons to the renal plexus.

sacral nerve

One of five pairs of dorsal or five pairs of ventral spinal nerves originating in the sacral segments of the spinal cord.

Sensory

The dorsal sacral spinal nerves innervate the skin and fascia over the sacrum and the medial gluteal region. The ventral sacral spinal nerves innervate the sacrospinous and sacrotuberous ligaments and the skin of the perineum.

Motor

The dorsal sacral spinal nerves innervate the lower multifidius muscles. The ventral sacral spinal nerves innervate the coccygeus and levator ani muscles.

sacral splanchnicnerve

A bundle of autonomic axons from the sympathetic trunk (ganglia S2–S3) that is en route to the inferior hypogastric plexus.

saphenous nerve

A sensory nerve that branches from the femoral nerve in the femoral triangle. It runs down the anterior and medial thigh and leg, accompanying the great saphenous vein, and it innervates the skin over the front and medial side of the knee, proximal leg, and medial side of the foot.

sciatic nerve

The largest nerve in the body. It originates in the sacral plexus and is composed of axons from spinal cord segments L4–S3. It runs along the back wall of the pelvis, exits through the greater sciatic foramen under the piriformis muscle, passes under the gluteus maximus muscle, and runs deeply along the posterior thigh. As it enters the popliteal fossa, its two internal components separate as the tibial and common peroneal nerves. The sciatic and its branches innervate the posterior thigh muscles (the flexors of the knee) and all the muscles, joints, and skin of the leg and foot.

second cranial nerve

Abbreviation: CN II
Optic nerve.

secretory nerve

A nerve that behaves like an endocrine gland by secreting neurohormones into the blood stream. Secretory neurons are a characteristic of the hypothalamus, where they release vasopressin, oxytocin, somatostatin, corticotropin-releasing hormone, and thyrotropin-releasing hormone.

sensory nerve

A nerve that conveys afferent information, e.g., visual information from the eye or proprioceptive information from a joint.

seventh cranial nerve

Abbreviation: CN VII
Facial nerve.

sinuvertebral nerve

Any of the small sensory branches of the spinal nerves that join with axons from sympathetic ganglia to innervate the dura, local blood vessels, periosteum, and ligaments of the spinal canal at each vertebral level. Synonym: recurrent meningeal nerve

sixth cranial nerve

Abbreviation: CN VI
Abducens nerve.

somatic nerve

A peripheral nerve that contains axons of the dorsal root ganglia or the cranial ganglia (i.e., somatic sensory nerves) or axons of the ventral horn or cranial nuclei motor neurons (i.e., somatic motor nerves). Somatic nerves innervate skin, skeletal muscles, and joints.

spinal accessory nerve

A motor nerve originating in the nucleus ambiguus in the medulla and in a column of motor neurons in the ventral horn of the upper cervical spinal cord. After exiting the skull through the jugular foramen, the nerve splits; its cranial trunk joins the vagus (CN X) and innervates striated muscles in the soft palate, pharynx, larynx, and esophagus; its spinal trunk continues down the neck to innervate the sternocleidomastoid and trapezius muscles. Synonym: accessory nerve; eleventh cranial nerve See: spinal accessory nucleus

SPINAL NERVES: Left side

SPINAL NERVES

spinal nerve

Any of the 31 sets of nerves originating in the spinal cord and emerging from the spinal canal through intervertebral foramina. Each spinal nerve is the concatenation of two sets of axons that emerge separately from the spinal cord: sensory axons (the dorsal root) and motor axons (the ventral root). See: illustrationillustration

splanchnic nerve

Any one of the paired, purely autonomic nerves from the thoracic sympathetic ganglia. The major splanchnic nerves are the greater, lesser, and least (smallest, renal) splanchnic nerves, which carry preganglionic sympathetic axons from ganglia 6–10 of the thoracic sympathetic trunk to the prevertebral ganglia (celiac, superior mesenteric, and aorticorenal ganglia) in the abdomen.

subcostal nerve

The ventral ramus of thoracic spinal nerve T12. It runs along the lower border of the twelfth rib and continues down through the abdominal muscles to reach the abdominal midline over the pubic symphysis. It innervates the skin and muscles in the area of the T12 dermatome.

suboccipital nerve

A motor nerve composed of axons from the dorsal ramus of spinal nerve C1. It leaves the spinal canal between the skull and the first cervical vertebra, and it innervates the four small muscles of the suboccipital triangle, deep in the back of the neck at the base of the skull.

subscapular nerve

Either of the upper and lower subscapular nerves from the shoulder nerves that originate in the posterior cord of the brachial plexus and are composed of axons from spinal cord segments C5–C6. They innervate the subscapularis and teres major muscles.

sudomotor nerve

A postganglionic sympathetic nerve that stimulates sweat glands.

superficial fibular nerve

Superficial peroneal nerve.

superficial peroneal nerve

One of the two major branches of the common peroneal nerve formed as the latter winds around the proximal neck of the fibula. The superficial peroneal nerve runs along the lateral leg, innervating the skin along the anterior surface of the leg and the dorsal surface of the foot and the peroneus longus and brevis muscles. Synonym: superficial fibular nerve

superior gluteal nerve

A nerve composed of axons from spinal nerves L4–S1. It follows the sciatic nerve out of the pelvis, and it innervates the gluteus medius, gluteus minimus, and tensor fasciae latae muscles.

supraorbital nerve

A sensory branch of the frontal nerve. It leaves the upper edge of the orbit through the supraorbital notch (or foramen) and divides into branches that innervate the conjunctiva lining the upper eyelid, the mucosa of the frontal sinus, and the skin of the upper eyelids, forehead, and front half of the scalp.

suprascapular nerve

A mixed shoulder nerve originating in the superior trunk of the brachial plexus and composed of axons from spinal cord segments C5–C6. It runs through the scapular notch under the superior transverse scapular ligament.

Sensory

It innervates the glenohumeral joint.

Motor

It innervates the supraspinatus and infraspinatus muscles.

supratrochlear nerve

A sensory branch of the frontal nerve. It leaves the upper edge of the orbit medial to the supraorbital nerve, and it innervates the skin of the middle of the forehead.

sural nerve

A sensory nerve composed of axons from the tibial and common fibular nerves in the posterior leg. It runs superficially along the posterior leg and lateral side of the foot and innervates the skin along its route.

sympathetic nerve

A nerve composed of axons of the sympathetic division of the autonomic nervous system. Sympathetic innervation is always a chain of two consecutive axons. The first axon, the preganglionic sympathetic axon, has its cell body in the intermediolateral column of spinal cord segments T1–L1; the first axon leaves the spinal cord through a ventral root and synapses in a peripheral sympathetic ganglion, either in the sympathetic trunk (the paraspinal ganglia) or in the prevertebral ganglia. The second axon in the chain, the postganglionic sympathetic axon, has its cell body in a peripheral ganglion, and it follows a splanchnic or other sympathetic nerve to its target tissue. The main transmitter used by preganglionic sympathetic axons is acetylcholine; for postganglionic sympathetic axons, it is norepinephrine. In general, stimulation of sympathetic nerves activates the body, putting it in "fight or flight" mode.

temporal nerve

1. Any of the two or three branches of the anterior division of the mandibular nerve (CN V3) that innervates the temporalis muscle. Synonym: deep temporal nerve2. Any the branches of the facial nerve (CN VII) that run over the zygomatic arch to innervate facial muscles of the upper eyelid and forehead.

tenth cranial nerve

Abbreviation: CN X
Vagus nerve.

third cranial nerve

Abbreviation: CN III
Oculomotor nerve.

thoracic nerve

Any of the twelve pairs of spinal nerves originating in the thoracic segments of the spinal cord. Each thoracic nerve emerges from the spinal canal through the intervertebral foramen below its corresponding vertebra. Thoracic spinal nerves innervate the trunk.

thoracodorsal nerve

A nerve originating in the posterior cord of the brachial plexus and composed of axons from spinal cord segments C6–C8. It runs inside the posterior axillary wall and along the lateral edge of the back to innervate the latissimus dorsi muscle.

tibial nerve

The continuation of the sciatic nerve beyond the apex of the popliteal fossa after the common fibular nerve has branched off. The tibial nerve runs alongside the tibial artery in the posterior leg; for most of its course, it is beneath the gastrocnemius and soleus muscles. Along its route, the tibial nerve innervates the posterior muscles of the knee and leg, and it ends, under the flexor retinaculum at the heel of the foot, by branching to form the medial and lateral plantar nerves.

trigeminal nerve

A mixed nerve arising from the pons in a large sensory root and a smaller motor root.

Sensory

Somatic sensory fibers from the face collect into three major trunks: the ophthalmic, from the region of the eyes and above; the maxillary, from the region of the lower eyelids and cheeks down to the upper lip, teeth, and gingivae; and the mandibular, from a region that follows the sideburns down along the jaw and that includes the lower lips, teeth, and gingivae. Neuronal cell bodies for these fibers are located in the trigeminal (Gasserian, semilunar) ganglion along the floor of the middle cranial fossa; the axons of the ganglion cells synapse in the pons and medulla.

Motor

Somatic motor axons originate in motor nuclei in the pons and, running only in the mandibular trunk of the trigeminal nerve, innervate the muscles used in chewing.

Course

The trigeminal nerve emerges from the pons via a large sensory root and a small adjacent motor root; both run together to the trigeminal ganglion. From the ganglion, three trunks leave the cranial cavity separately: the ophthalmic trunk (ophthalmic nerve, CN V1) enters the back of the orbit through the superior orbital fissure, the maxillary trunk (maxillary nerve, CN V2) leaves through the foramen rotundum, and the mandibular trunk (mandibular nerve, CN V3) leaves through the foramen ovale.

Synonym: fifth cranial nerve

trochlear nerve

A somatic motor nerve originating in the trochlear nucleus in the midbrain. The nerve leaves the midbrain just behind the inferior colliculus; it crosses dorsally, and then runs in the subarachnoid space and the cavernous sinus until it enters the back of the orbit through superior orbital fissure. It innervates the superior oblique muscle. Synonym: fourth cranial nerve

twelfth cranial nerve

Abbreviation: CN XII
Hypoglossal nerve.

tympanic nerve

Any of the small nerves from the tympanic plexus, which lies along the lower medial wall of the tympanic cavity. They innervate the mucosa of the tympanic cavity, Eustachian tube, and mastoid air cells.

ulnar nerve

A mixed nerve of the upper limb originating in the medial cord of the brachial plexus and composed of axons from spinal cord segments C7–T1.

Sensory

It innervates the skin of the last 1 1/2 digits and the palm proximal to them.

Motor

In the forearm, it innervates the flexor digitorum profundus, abductor digiti minimi, flexor carpi ulnaris, and flexor digiti minimi. In the hand, it innervates most of the intrinsic muscles (the hypothenar, interosseous, adductor pollicis, deep head of the flexor pollicis brevis, opponens digiti minimi, and palmaris brevis muscles and the medial lumbricals of digits 4 and 5).

Course

It runs along the medial side of the anterior forearm. It becomes superficial near the wrist and passes into the hand above (superficial to) the flexor retinaculum.

unmyelinated nerve

, nonmyelinated nervePeripheral axons that are surrounded by Schwann cells but are not enwrapped by rolls of Schwann cell membrane; extensions of the Schwann cells isolate unmyelinated axons from each other. Unmyelinated axons are small in diameter and transmit signals more slowly than myelinated axons.

uterine nerve

Any of the autonomic nerves innervating the uterus. They emerge from the inferior hypogastric plexus and follow the uterine arteries; in the uterus, the axons distribute throughout the myometrium and endometrium.

vagus nerve

A nerve that arises from the medulla and has branches to many organs

Sensory

Visceral sensory fibers from the lower pharynx, larynx, thoracic organs, and abdominal viscera join proprioceptive sensory fibers from the muscles of the soft palate, pharynx, and larynx and sensory taste fibers from the root of the tongue and the epiglottis. These axons enter the vagus nerve along its length and run to the superior and inferior (nodosal) ganglia of the vagus nerve; these ganglia lie within and just below the jugular foramen of the skull. The axons of cell bodies in the ganglia then take the vagus nerve to their various synaptic sites in the medulla.

Motor

Somatic motor axons from hindbrain motor nuclei run in the vagus nerve and innervate the soft palate, pharynx, and larynx. Preganglionic parasympathetic axons from the dorsal motor nucleus of the vagus take the vagus nerve to provide most of the parasympathetic innervation of the body below the neck and above the pelvis, including the lungs, heart, and abdominal viscera.

Course

The vagus forms from a line of small rootlets along the lower medulla; the rootlets collect into a single nerve, which emerges from the skull through the jugular foramen, along with the glossopharyngeal (CN IX) and spinal accessory (CN XI) nerves. The vagus nerve continues caudally in the carotid sheath between the internal jugular vein and the carotid artery, giving off branches along the way. It then joins the esophageal plexus and continues along the esophagus as it passes through the diaphragm; in the abdomen, the vagus nerve splits into branches that innervate all the abdominal viscera.

Synonym: tenth cranial nerveillustration

vasoconstrictor nerve

A sympathetic nerve that stimulates the constriction of smooth muscle cells in arterial walls.

vasodilator nerve

A nerve conducting impulses that bring about dilation of a blood vessel.

vasomotor nerve

A nerve that controls the caliber of a blood vessel; a vasoconstrictor or vasodilator nerve. Synonym: nervi vasorum.

vasosensory nerve

Any nerve providing sensory fibers for a vessel.

vestibular nerve

The component of the vestibulocochlear nerve (CN VIII) with axons carrying sensory information about equilibrium and spatial orientation; it connects the vestibular ganglion with the vestibular nuclei in the brainstem.

vestibulocochlear nerve

The eighth cranial nerve, a sensory nerve for hearing and equilibrium. Cell bodies of the vestibular neurons are located in the vestibular ganglion in the inner ear; their receptor terminals end in the saccule, utricle, and semicircular ducts. Cell bodies of the cochlear neurons are located in the spiral ganglion in the inner ear; their receptor terminals end in the spiral organ of Corti. Axons of the neuron cell bodies in the vestibular and spiral ganglia run to the CNS side-by-side in the petrous process of the temporal bone; they exit through the internal acoustic meatus and enter the brainstem at the junction of the pons and the medulla. See: illustration

vidian nerve

A short efferent nerve formed from the merger of the deep petrosal and greater petrosal nerves. The vidian nerve carries postganglionic sympathetic axons from the superior cervical ganglion and preganglionic parasympathetic axons from the superior salivatory nucleus (in the pons); it also carries taste axons from the palate. The vidian nerve exits the skull through the pterygoid (vidian) canal and connects to the pterygopalatine ganglion inside pterygopalatine fossa. Synonym: nerve of the pterygoid canal

visceral nerve

A peripheral nerve that contains axons of the autonomic nervous system, either transmitting afferent signals from mucous membranes, glands, and vessels (visceral sensory nerves) or transmitting efferent signals to smooth muscles and glands (visceral motor nerves). Visceral motor nerves always synapse in a ganglion between their origin in the central nervous system and their termination in a muscle or gland.

zygomatic nerve

1. A sensory branch of the maxillary nerve (CN V2). It divides into the zygomaticofacial and zygomaticotemporal nerves along the floor of the orbit; these nerves innervate the skin of the cheeks. 2. Any of the motor branches of the facial nerve (CN VII) that run roughly horizontally through the cheek and innervate the facial muscles between the mouth and the lower eyelid.

acoustic nerve

The short, eighth, cranial nerve connecting each inner ear to the brain and carrying nerve impulses subserving hearing and balance. Also known as the auditory nerve. The acoustic nerve is sometimes the seat of a non-cancerous but dangerous tumour, an ACOUSTIC SCHWANNOMA, which can cause much local damage by compression and which is not readily accessible for removal.