nerve
(nĕrv 
)
[L. nervus, sinew]
Parallel axons running together inside an epineurium (thick connective tissue sheath). In the nerve, axons are wrapped into small bundles by endoneuria (thin connective tissue sheaths); 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 central nervous system (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; illus.
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 gland ular 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 n.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. SYN: abducent nerve; sixth cranial nerve.
SEE: cranial nerve.
accelerator n.A sympathetic nerve to the heart that carries impulses that speed the heart rate.
accessory n.Spinal accessory nerve.
SEE: cranial nerve for illus.
SEE: illus.
adrenergic n.A nerve that uses a catecholamine as its main neurotransmitter.
afferent n.A nerve that conducts impulses toward the brain or spinal cord.
SEE: sensory nerve.
alveolar n.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 mand ibular canal, giving off branches to the lower teeth and gingivae as it passes. SYN: dental nerve.
antebrachial cutaneous n.A cutaneous nerve of the forearm.
SEE: lateral antebrachial cutaneous nerve; medial antebrachial cutaneous nerve; posterior antebrachial cutaneous nerve.
auditory n.The components of the eighth cranial nerve (CN VIII) carrying axons that convey information regarding sound and balance between the spiral ganglion in the inner ear and the cochlear nuclei in the brainstem. SYN: acoustic nerve; cochlear nerve; eighth cranial nerve; vestibulocochlear nerve.
auricular n.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 n.A sensory branch of the mand ibular 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 n.A visceral motor (visceral efferent) nerve, innervating smooth muscle, cardiac muscle, or gland s. Visceral motor nerves can contain pre- or postganglionic sympathetic or parasympathetic axons.
axillary n.A mixed nerve of the posterior aspect of the arm originating from the posterior cord of the brachial plexus and composed of axons from spinal cord segments C5–C6.
Innervates skin over the shoulder and inferior aspect of the deltoid.
Innervates the teres minor and deltoid muscles.
SEE: lateral brachial cutaneous nerve; medial brachial cutaneous nerve; posterior brachial cutaneous nerve.
buccal n.1A branch of the mand ibular nerve (CN V3).
It innervates skin over the lower cheek, mucous membranes inside the cheek, and the buccal gingivae along the second and third lower molars.
It innervates the lateral pterygoid muscle.
2A motor branch of the facial nerve (CN VII) that innervates the buccinator and neighboring facial muscles.calcaneal n.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 n.Any of the nerves traveling to the cardiac plexus that contain primarily autonomic fibers. The superior cardiac nerve, middle cardiac nerve, and inferior cardiac nerve originate in the superior, middle, and inferior cervical sympathetic ganglia and convey postganglionic sympathetic fibers. The preganglionic parasympathetic innervation of the cardiac plexus is from the vagus nerve (CN X).
carotid n.1Any 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.2Carotid sinus nerve.
carotid sinus n.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). SYN: carotid nerve.
cervical n.1Any 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.2A 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 n.A nerve that uses acetylcholine as its main neurotransmitter.
ciliary n.Either of two nerve types (long ciliary nerves, short ciliary nerves) that are indirect branches of the ophthalmic division of the trigeminal nerve. They carry sensory axons and postganglionic sympathetic fibers. The short ciliary nerves also convey postganglionic parasympathetic fibers originating in the ciliary ganglion.
coccygeal n.One of a pair of nerves arising from the coccygeal section of the spinal cord, and the inferiormost of the spinal nerves.
collateral n.An offshoot nerve composed of branches of some of the axons in the main nerve.
common fibular n.Common peroneal nerve.
common peroneal n.An older term for the common fibular nerve, one of the two divisions of the sciatic nerve in the lower limb. The sciatic nerve branches into the tibial and common fibular (peroneal) nerves in the apex of the popliteal fossa. The common fibular nerve winds around the proximal neck of the fibula to reach the anterior leg where it divides into the superficial and deep fibular nerves. The common fibular nerve innervates the knee joint and the skin of the lateral aspect of the leg. SYN: common fibular nerve.
ABBR: CN
Any of the 12 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: illus.
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): Chronic facial pain.
Pain or loss of sensation in the face.
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 n.A nerve that mainly provides sensory innervation to the skin.
deep fibularn.Deep peroneal nerve.
deep peroneal n.One of the two major branches of the common fibular (peroneal) nerve formed as the latter winds around the proximal neck of the fibula. The deep fibular (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. SYN: deep fibular nerve.
deep petrosal n.A bundle of postganglionic sympathetic axons from the superior cervical ganglion. These axons invest the internal carotid artery 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 pterygoid canal, en route to the pterygopalatine ganglion.
deep temporal n.Temporal nerve (1).
depressor n.Any nerve whose stimulation depresses the activity of an organ or nerve center.
digital n.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 n. 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 n. of the penis A branch of the pudendal nerve that transmits sensory information from the penis.
dorsal scapular n.A branch of spinal nerve C5, which runs in the posterior aspect of the shoulder and innervates the rhomboid muscles.
efferent n.A nerve conducting impulses away from the brain or spinal cord. SYN: motor nerve.
ABBR: CN VIII
Auditory nerve.ABBR: CN XI
Spinal accessory nerve.ethmoidal n.Either of two nerves, the anterior ethmoidal nerve or the posterior ethmoidal nerve, that are sensory branches of the nasociliary nerve.
excitatory n.A nerve that heightens, increases, or starts the activity of its target.
excitoreflex n.A visceral nerve whose stimulation causes reflex action.
facial n.A mixed nerve consisting of somatic motor fibers supplying the muscles of facial expression, visceral motor fibers supplying the submand ibular and sublingual gland s, the nasal and oral mucosae, and the lacrimal gland ; and of afferent fibers from taste buds of the anterior two thirds of the tongue and muscles.
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 into the pons where they synapse in the nucleus of the tractus solitarius. There is a small somatosensory component from the external ear.
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 submand ibular ganglion by following the lingual nerve. Other preganglionic parasympathetic axons follow the greater petrosal nerve and the nerve of the pterygoid canal to reach the pterygopalatine ganglion
SYN: seventh cranial nerve.SEE: illus.; cranial nerve.
femoral n.1A 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 following muscles: the adductor longus, adductor brevis, gracilis, pectineus, obturator externus, and adductor magnus.
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.
The femoral nerve and its branches innervate the pectineus, sartorius, and quadriceps muscles.
2A sensory branch of the genitofemoral nerve that runs in the femoral sheath and innervates skin over the femoral triangle. SYN: crural nerve.ABBR: CN V
Trigeminal nerve.ABBR: CN I
Olfactory nerve.ABBR: CN IV
Trochlear nerve.frontal n.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 n.A nerve that uses gamma-aminobutyric acid (GABA ) as its main neurotransmitter.
gangliated n.Any nerve of the sympathetic nervous system.
gastric n.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 n.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 n.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 n.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.
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.
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.
CN IX.
SYN: ninth cranial nerve.SEE: illus.
greater occipital n.A prominent sensory component of the dorsal (posterior) 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. SYN: occipital nerve.
greater petrosal n.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, passes through foramen lacerum, and merges with the deep petrosal nerve to form the vidian nerve of the pterygoid canal. SYN: greater superficial petrosal nerve; major superficial petrosal nerve.
greater superficial petrosal n.Greater petrosal nerve.
hepatic n.Any of the nerves forming the hepatic plexus that supply autonomic innervation to the liver and biliary system.
hypoglossal n.A nerve that carries somatic motor nerve fibers 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). SYN: twelfth cranial nerve.
iliohypogastric n.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 n.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 n.A mixed nerve of axons from spinal nerves L5–S2. It exits the pelvis via the greater sciatic foramen, inferior to the piriformis muscle and innervates the gluteus maximus muscle.
inferior rectal n.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 n.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 n.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 n.A nerve that dampens, decreases, or stops the activity of its target.
intercostal n.Any of the eleven pairs of parallel nerves originating in the anterior rami of thoracic spinal nerves T1–T11. Each intercostal nerve runs anteriorly in the intercostal space with a companion intercostal artery and vein along the inferior border of the rib in the costal groove. It innervates the intercostal muscles and overlying skin.
intermediate n.Nervus intermedius.
lacrimal n.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 n.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 n.A sensory nerve that innervates the skin along the entire lateral surface of the forearm. It is the terminal branch of the musculocutaneous nerve. SYN: lateral cutaneous nerve of the forearm.
lateral brachial cutaneous n.A sensory branch of the axillary nerve that innervates the skin over the lateral lower edge of the deltoid muscle. SYN: lateral cutaneous nerve of the arm.
lateral cutaneous n. of the arm Lateral brachial cutaneous nerve.
lateral cutaneous n. of the forearm Lateral antebrachial cutaneous nerve.
lateral femoral cutaneous n.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 n.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 n.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.
It innervates the skin on the lateral one-third of the sole and on the plantar side of the last 1 1/2 toes.
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 n.A sensory nerve composed of axons from spinal cord segments C2–C3. It innervates the skin over the back of the neck.
lingual n.lingual nerve A sensory branch of the mand ibular division of the trigeminal nerve (CN V3). lt is joined by the chorda tympani before entering the lateral aspect of the floor of the oral cavity. The lingual nerve then runs toward the front of the mand ible, between the hyoglossus and mylohyoid muscles, and ends near the front of the base of the tongue. It innervates the submand ibular ganglion, the mucosa along the base of the mouth, the anterior two thirds of the tongue, and the inner lower gingivae.
long thoracic n.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 n.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 n.Bundles of sympathetic axons from the lumbar ganglia of the sympathetic trunk that run to the inferior mesenteric and hypogastric plexuses.
major superficial petrosal n.Greater petrosal nerve.
ABBR: CN V3
1The inferior trunk of the trigeminal cranial nerve. The mand ibular nerve is both sensory and motor.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.
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), mylohyoid, anterior belly of the digastric, tensor tympani, and tensor palati.
The mand ibular 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 n.A motor branch of the mand ibular nerve (CN V3) that innervates the masseter muscle and the temporomand ibular joint.
ABBR: 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. The maxillary nerve leaves the skull and enters the pterygopalatine fossa via the foramen rotundum.medial antebrachial cutaneous n.A sensory nerve originating in the medial cord of the brachial plexus, composed of axons from spinal cord segments C8–T1, and innervating the skin on the medial side of the forearm. SYN: medial cutaneous nerve of the forearm.
medial brachial cutaneous n.A sensory nerve originating from the medial cord of the brachial plexus, composed of axons from spinal cord segments C8–T1, and innervating the skin on the medial side of the arm. SYN: medial cutaneous nerve of the arm.
medial cutaneous n. of the arm Medial brachial cutaneous nerve.
medial cutaneous n. of the forearm Medial antebrachial cutaneous nerve.
medial pectoral n.A nerve originating in the medial cord of the brachial plexus, composed of axons C8–T1, and innervating the pectoralis minormuscle and a portion of the pectoralis major muscle.
medial plantar n.A mixed nerve that is a terminal branch of the tibial nerve and that runs along the sole of the foot.
It innervates the skin on the medial two-thirds of the sole and the plantar side of the first 3 1/2 toes.
It innervates the abductor hallucis, flexor digitorum brevis, flexor hallucis brevis, and first lumbrical muscles.
median n.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.
It innervates the skin of the first 3 1/2 digits and the palm proximal to them.
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.
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 n.The terminal branch of the inferior alveolar nerve. It runs in the mand ibular canal, emerges through the mental foramen, and innervates the mucosa of the lower lip and the skin of the lower lip and chin.
mixed n.A nerve containing both afferent (sensory) and efferent (motor) axons.
motor n.A nerve conveying efferent information to an effector target, such as a muscle or a gland . SYN: efferent nerve.
musculocutaneous n.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.
Distal to the elbow, it becomes the lateral antebrachial cutaneous nerve, which innervates the skin and fascia of the lateral half of the forearm.
It innervates the coracobrachialis, biceps brachii, and brachialis muscles.
It runs between the biceps brachii and brachialis muscles.
myelinated n.A nerve containing axons wrapped in myelin. Myelinated axons transmit signals more rapidly than unmyelinated fibers.
mylohyoid n.A motor branch of the inferior alveolar nerve that arises just proximal to the mand ibular foramen. It innervates the mylohyoid muscle and the anterior belly of the digastric muscle.
nasal n.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 n.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 n.A branch of the maxillary nerve that carries both sensory and autonomic fibers from the pterygopalatine ganglion through the adjacent sphenopalatine foramen into the roof of the posterior aspect of the 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.
ABBR: CN IX
Glossopharyngeal nervenoradrenergic n.A nerve that uses norepinephrine as its main neurotransmitter.
obturator n.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 n.Greater occipital nerve.
oculomotor n.A nerve that carries somatic and visceral motor fibers that originate in the oculomotor nucleus of the midbrain and the adjacent accessory oculomotor 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 several muscles that move the eye: the superior, medial, and inferior recti, the inferior oblique, and the levator palpebrae superioris. 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. SYN: third cranial nerve.
olfactory n.Any nerve of the meshwork of sensory nerves that have neuronal cell bodies, are located in the olfactory epithelium, and supply the nasal olfactory mucosa. Axons from the receptor cells join into approximately 20 small nonmyelinated bundles. These bundles pass into the skull through holes in the cribriform plate of the ethmoid bone and terminate in the ipsilateral olfactory bulb in the olfactory glomeruli. SYN: first cranial nerve.
SEE: cranial nerve; olfactory epithelium; olfactory glomerulus.
ABBR: 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 n.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. SYN: second cranial nerve.
palatine n.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 n.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 n.A nerve that contains axons of the parasympathetic division of the autonomic nervous system in addition to other fiber types. 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 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. Both preganglionic and postganglionic parasympathetic axons use acetylcholine as the neurotransmitter.
SEE: lateral pectoral nerve; medial pectoral nerve.
pelvic splanchnic n.A bundle of nerves from spinal cord segments S2–S4 that are en route to the inferior hypogastric plexus. They contain preganglionic parasympathetic and visceral afferent fibers. SYN: nervus erigens.
peptidergic n.A nerve that uses a peptide, e.g., substance P, as its main neurotransmitter.
perineal n.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 n.A nerve outside the central nervous system, wrapped in a connective tissue sheath.
perivascular n.Any of the sympathetic fibers surrounding and innervating blood vessels. SYN: perivascular nerve plexus.
pharyngeal n.1A nerve from the pterygopalatine ganglion that conveys postganglionic parasympathetic fibers to the mucosa of the nasopharynx.2A nerve from the superior cervical ganglia that conveys postganglionic sympathetic fibers to the pharynx and its surrounding pharyngeal plexus.
phrenic n.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 n.A motor nerve that innervates the erector pili muscles of hair follicles.
posterior antebrachial cutaneous n.A sensory branch of the radial nerve that innervates a strip of skin along the posterior surface (back) of the forearm. SYN: posterior cutaneous nerve of the forearm.
posterior brachial cutaneous n.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. SYN: posterior cutaneous nerve of the arm.
posterior cutaneous n. of the arm Posterior brachial cutaneous nerve.
posterior cutaneous n. of the forearm Posterior antebrachial cutaneous nerve.
posterior cutaneous n. of the thigh Posterior femoral cutaneous nerve.
posterior femoral cutaneous n.A nerve containing sensory fibers that originates in the sacral plexus and is 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. SYN: posterior cutaneous nerve of the thigh.
presacral n.Superior hypogastric plexus.
n. of the pterygoid canal Vidian nerve.
pressor n.An afferent nerve whose stimulation excites the vasoconstrictor center, thus increasing the blood pressure.
pudendal n.A mixed nerve composed of axons from spinal nerves S2–S4. It follows the sciatic nerve out of the pelvis but immediately enters the perineum through the lesser sciatic foramen by wrapping around the sacrospinous ligament. It innervates most of the structures of the perineum; its branches include the inferior rectal, perineal, dorsal nerves of the penis or clitoris and posterior scrotal or labial nerves.
pulmonary n.Any of the sympathetic and parasympathetic nerves from the pulmonary plexus that innervate the bronchial muscles, gland s, mucous membranes, and alveoli.
purinergic n.A nerve with axons that secrete adenosine triphosphate (ATP) or other purine nucleotides as a neurotransmitter or as a local chemical modulator.
radial n.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.
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.
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 minimi, and abductor digiti minimi muscles.
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.
SYN: musculospiral nerve.recurrent laryngeal n.A branch of the vagus nerve (CN X). On the right, it branches from the vagus and loops under the subclavian artery; 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. It is also sensory to the mucosa below the vocal folds. Injuries of the recurrent laryngeal nerve cause hoarseness, dysphagia, and dyspnea.
recurrent meningeal n.Sinuvertebral nerve.
renal n.A nerve that carries preganglionic sympathetic axons to the renal plexus.
sacral n.One of five pairs of dorsal or five pairs of ventral spinal nerves originating in the sacral segments of the spinal cord.
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.
The dorsal sacral spinal nerves innervate the lower multifidius muscles. The ventral sacral spinal nerves innervate the coccygeus and levator ani muscles.
sacral splanchnic n.A bundle of autonomic axons from the sympathetic trunk (ganglia S2–S3) that is en route to the inferior hypogastric plexus.
saphenous n.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 n.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.
ABBR: CN II
Optic nerve.secretory n.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 n.A nerve that conveys afferent information, e.g., visual information from the eye or proprioceptive information from a joint.
ABBR: CN VII
Facial nerve.sinuvertebral n.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. SYN: recurrent meningeal nerve.
ABBR: CN VI
Abducens nerve.small sciatic n.The posterior femoral cutaneous nerve, supplying the skin of the buttocks, perineum, popliteal region, and the back of the thigh and the leg.
somatic n.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 n.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 [posterior] root) and motor axons (the ventral [anterior] root).
SEE: illus.
spinal accessory n.A purely motor nerve that supplies the trapezius and sternocleidomastoid. The cell bodies of origin are found in the spinal cord (C1–C4). Efferent fibers pass superiorly through the foramen magnum into the cranial vault and exit via the jugular foramen. SYN: accessory nerve; eleventh cranial nerve.
SEE: spinal accessory nucleus.
splanchnic n.Any of the paired branches from the sympathetic chain that convey sympathetic fibers and visceral afferents or from S2–S4 spinal nerves that convey parasympathetic fibers and visceral afferents. 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 n.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 n.The posterior ramus of C1 spinal nerve, containing motor fibers. It leaves the spinal canal between the skull and the first cervical vertebra; it innervates the four small muscles of the suboccipital triangle, deep in the back of the neck at the base of the skull.
subscapular n.Either of the upper and lower nerves from the posterior cord of the brachial plexus. They are composed of axons from spinal cord segments C5–C6 and innervate the subscapularis and teres major muscles.
sudomotor n.A nerve that contains postganglionic sympathetic fibers that stimulate sweat gland s.
superficial fibular n.Superficial peroneal nerve.
superficial peroneal n.One of the two major branches of the common peroneal nerve formed as the common nerve 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 (fibularis) longus and braves muscles. SYN: superficial fibular nerve.
superior gluteal n.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 n.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 n.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.
It innervates the glenohumeral joint.
It innervates the supraspinatus and infraspinatus muscles.
supratrochlear n.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 n.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 n.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–L2; the first axon leaves the spinal cord through a ventral (anterior) root and synapses in a peripheral sympathetic ganglion, either in the sympathetic trunk (the paravertebral 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 n.1Any of the two or three branches of the anterior division of the mand ibular nerve (CN V3) that innervates the temporalis muscle. SYN: deep temporal nerve.2Any of the branches of the facial nerve (CN VII) that run over the zygomatic arch to innervate facial muscles of the upper eyelid and forehead.
ABBR: CN X
Vagus nerve.ABBR: CN III
Oculomotor nerve.thoracic n.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 n.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 n.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 along the tibial artery in the posterior leg; for most of its course, it is deep to 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 n.A mixed nerve arising from the pons in a large sensory root and a smaller motor root.
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 mand ibular, 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.
Somatic motor axons originate in motor nuclei in the pons and , running only in the mand ibular trunk of the trigeminal nerve, innervate the muscles used in chewing.
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 mand ibular trunk (mand ibular nerve, CN V3) leaves through the foramen ovale.
SYN: fifth cranial nerve.trochlear n.A somatic motor nerve originating in the trochlear nucleus in the midbrain. The nerve leaves the midbrain just behind the inferior colliculus; it 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 contralaterally as its fibers cross the midline before exiting the brainstem. SYN: fourth cranial nerve.
ABBR: CN XII
Hypoglossal nerve.tympanic n.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 (auditory) tube, and mastoid air cells. SYN: Jacobson nerve.
ulnar n.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.
It innervates the skin of the last 1 1/2 digits and the palm proximal to them.
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).
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.
Variant: nonmyelinated nerve
Peripheral 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 n.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 n.A nerve that arises from the medulla and has branches to many organs.
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 (nodose) 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.
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.
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.
SYN: tenth cranial nerve.vasoconstrictor n.A sympathetic nerve that stimulates the constriction of smooth muscle cells in arterial walls.
vasodilator n.A nerve conducting impulses that bring about dilation of a blood vessel.
vasomotor n.A nerve that controls the caliber of a blood vessel; a vasoconstrictor or vasodilator nerve. SYN: vasomotor nerve.
vasosensory n.Any nerve providing sensory fibers for a vessel.
vestibularn.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 n.Auditory nerve.
vidian n.A short 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. SYN: nerve of the pterygoid canal.
visceral n.A peripheral nerve that contains axons transmitting either afferent signals from mucous membranes, gland s, and vessels (visceral sensory nerves) or efferent (autonomic) signals to smooth muscles and gland s. 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 n.1A 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.2Any 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.