efferent nerve

(noun)

Nerves that conduct signals from the central nervous system along motor neurons to their target muscles and glands.

Related Terms

Examples of efferent nerve in the following topics:

  • Classification of Nerves

    • Nerves are primarily classified based on their direction of travel to or from the CNS, but they are also subclassified by other nerve characteristics.
    • Mixed nerves contain both afferent and efferent axons, and thus conduct both incoming sensory information and outgoing muscle commands in the same nerve bundle.
    • Cranial nerves innervate parts of the head and connect directly to the brain.
    • Cranial nerves are typically assigned Roman numerals from 0 to 12.
    • Schematic of efferent and afferent nerve transmission to and from peripheral tissue and spinal cord.

  • Abducens (VI) Nerve

    • The abducens nerve (cranial nerve VI) controls the lateral movement of the eye through innervation of the lateral rectus muscle.
    • The abducens nerve (cranial nerve VI) is a somatic efferent nerve that, in humans, controls the movement of a single muscle: the lateral rectus muscle of the eye that moves the eye horizontally.
    • The abducens nerve leaves the brainstem at the junction of the pons and the medulla, medial to the facial nerve.
    • The nerve enters the subarachnoid space when it emerges from the brainstem.
    • Schematic of cranial nerves showing cranial nerve VI, the abducens nerve.

  • Structure of a Nerve

    • A nerve provides a structured pathway that supports the electrochemical nerve impulses transmitted along each of the axons.
    • Neurons are sometimes referred to as nerve cells, although this term is misleading since many neurons do not occupy nerves, and nerves also include non-neuronal support cells (glial cells) that contribute to the health of enclosed neurons.
    • A nerve conveys information in the form of electrochemical impulses (known as nerve impulses or action potentials) carried by the individual neurons that make up the nerve.
    • Thus they are synonymous with afferent nerves.
    • Thus they are synonymous with efferent nerves.

  • Function and Physiology of the Spinal Nerves

    • The phrenic nerve arises from nerve roots C3, C4, and C5.
    • PNS nerves are involved in the erection of genital tissues via the pelvic splanchnic nerves 2–4.
    • The somatic nervous system consists of afferent and efferent nerves and is associated with the voluntary control of skeletal muscle movements.
    • The afferent nerves are responsible for relaying sensations from the body to the central nervous system (CNS), while the efferent nerves are responsible for sending out commands from the CNS to the body to stimulate muscle contraction. 
    • Numbers indicate the types of nerve fibers: 1 somatic efferent, 2 somatic afferent, 3–5 sympathetic efferent, 6–7 sympathetic afferent.

  • Glossopharyngeal (IX) Nerve

    • The glossopharyngeal nerve (cranial nerve IX) serves many distinct functions, including providing sensory innervation to various  head and neck structures.
    • The glossopharyngeal nerve is the ninth of 12 pairs of cranial nerves.
    • There are a number of functions of the glossopharyngeal nerve.
    • The various functions of the glossopharyngeal nerve are that:
    • Visceral motor (general visceral efferent): Provides parasympathetic innervation of the parotid gland.

  • Facial (VII) Nerve

    • The facial nerve (cranial nerve VII) determines facial expressions and the taste sensations of the tongue.
    • The facial nerve is the seventh (cranial nerve VII) of the 12, paired cranial nerves.
    • The motor part of the facial nerve arises from the facial nerve nucleus in the pons, while the sensory part of the facial nerve arises from the nervus intermedius.
    • Although it passes through the parotid gland, it does not innervate the gland (this is the responsibility of cranial nerve IX, the glossopharyngeal nerve).
    • The efferent arc occurs via the facial nerve.

  • Overview of the Spinal Nerves

    • The dorsal roots carry afferent sensory axons, while the ventral roots carry efferent motor axons.
    • The posterior distribution of the cervical nerves includes the suboccipital nerve (C1), the greater occipital nerve (C2), and the third occipital nerve (C3).
    • The subcostal nerve comes from nerve T12, and runs below the twelfth rib.
    • The sacral nerves have both afferent and efferent fibers, thus they are responsible for part of the sensory perception and the movements of the lower extremities of the human body.
    • These pathways have both afferent and efferent fibers.

  • Parasympathetic (Craniosacral) Division

    • Example nerves supplying parasympathetic fibers to the parasympathetic ganglia of the head include the oculomotor nerve (ciliary ganglion); the facial nerve (pterygopalatine ganglion, submandibular ganglion); the glossopharyngeal nerve (otic ganglion); the vagus nerve (no named ganglion); and the pelvic splanchnic nerves (no named ganglion).
    • The motor root carries presynaptic parasympathetic nerve fibers (general visceral efferent fibers) that terminate in the ganglion by synapsing the postsynaptic fibers traveling to target organs.
    • The sympathetic root carries postsynaptic sympathetic fibers (general visceral efferent fibers) that traverse the ganglion without synapsing.
    • Nerves supplying parasympathetic fibers to the parasympathetic ganglia of the head include the oculomotor nerve (ciliary ganglion), the facial nerve (pterygopalatine ganglion, submandibular ganglion), the glossopharyngeal nerve (otic ganglion), the vagus nerve, and the pelvic splanchnic nerves.
    • The parasympathetic division has craniosacral "outflow," meaning that the neurons begin at the cranial nerves (CN3, CN7, CN9, CN10) and sacral (S2-S4) spinal cord.

  • Pons

    • The alar plate produces sensory neuroblasts, which will give rise to the solitary nucleus and its special visceral afferent column, the cochlear and vestibular nuclei (which form the special somatic afferent fibers of the vestibulocochlear nerve), the spinal and principal trigeminal nerve nuclei (which form the general somatic afferent column of the trigeminal nerve), and the pontine nuclei, which is involved in motor activity.
    • Basal plate neuroblasts give rise to the abducens nucleus (forms the general somatic efferent fibers), the facial and motor trigeminal nuclei (form the special visceral efferent column), and the superior salivatory nucleus, which forms the general visceral efferent fibers of the facial nerve.
    • A number of cranial nerve nuclei are present in the pons:
    • The chief or pontine nucleus of the trigeminal nerve sensory nucleus (V)- mid-pons
    • The functions of the four nerves of the pons include sensory roles in hearing, equilibrium, taste, and facial sensations such as touch and pain.

  • Plexuses

    • A nerve plexus is a network of intersecting nerves  that serve the same part of the body.
    • A nerve plexus is a network of intersecting nerves; multiple nerve plexuses exist in the body.
    • Nerve plexuses are composed of afferent and efferent fibers that arise from the merging of the anterior rami of spinal nerves and blood vessels.
    • The brachial plexus is formed by the ventral rami of C5–C8 and the T1 spinal nerves, and lower and upper halves of the C4 and T2 spinal nerves.
    • The lumbar plexus is comprised of the ventral rami of the lumbar spinal nerves (L1–L5) and a contribution from thoracic nerve (T12).