abducens nerve

(noun)

A nerve that controls the lateral rectus muscle in the eye.

Related Terms

Examples of abducens nerve in the following topics:

  • 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.
    • Homologous abducens nerves are found in all vertebrates except lampreys and hagfishes.
    • The abducens nerve leaves the brainstem at the junction of the pons and the medulla, medial to the facial nerve.
    • Schematic of cranial nerves showing cranial nerve VI, the abducens nerve.

  • Brief Overview of Cranial Nerves

    • Cranial nerves are the nerves that emerge directly from the brain (including the brainstem).
    • The terminal nerves, olfactory nerves (I) and optic nerves (II) emerge from the cerebrum or forebrain, and the remaining ten pairs arise from the brainstem, which is the lower part of the brain.
    • The optic nerve (II): This nerve carries visual information from the retina of the eye to the brain.
    • The abducens nerve (VI): A motor nerve that innervates the lateral rectus muscle of the eye, which controls lateral movement.
    • The hypoglossal nerve (XII): This nerve controls the tongue movements of speech, food manipulation, and swallowing.

  • 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.

  • Strabismus

    • Strabismus can be caused when the cranial nerves III (oculomotor), IV (trochlear), or VI (abducens) have a lesion.
    • A strabismus caused by a lesion in either of these nerves results in the lack of innervation to eye muscles and results in a change of eye position.
    • Detailed view of nerves of lateral orbit showing the ciliary ganglion immediately behind the globe of the eye.

  • Trochlear (IV) Nerve

    • The trochlear nerve (cranial nerve IV) is a motor nerve that innervates a single muscle: the superior oblique muscle of the eye.
    • The trochlear nerve (cranial nerve IV) is a motor nerve that innervates a single muscle: the superior oblique muscle of the eye.
    • The trochlear nerve is unique among the cranial nerves in several respects.
    • Other than the optic nerve (cranial nerve II), it is the only cranial nerve that decussates (crosses to the other side) before innervating its target.
    • Lesions of all other cranial nuclei affect the ipsilateral side (except of course the optic nerve, cranial nerve II, which innervates both eyes).

  • Accessory (XI) Nerve

    • The accessory nerve (cranial nerve XI) controls the muscles of the shoulder and neck.
    • The accessory nerve (cranial nerve XI) controls the sternocleidomastoid and trapezius muscles of the shoulder and neck.
    • Unlike the other 11 cranial nerves, the accessory nerve begins outside the skull.
    • Due to its unusual course, the accessory nerve is the only nerve that enters and exits the skull.
    • However, more modern characterizations of the nerve regard the cranial component as separate and part of the vagus nerve.

  • Olfactory (I) Nerve

    • The olfactory nerve, or cranial nerve I, is the first of 12 cranial nerves and is responsible for the sense of smell.
    • The olfactory nerve, or cranial nerve I, is the first of the 12 cranial nerves.
    • The olfactory nerve is the shortest of the 12 cranial nerves and only one of two cranial nerves (the other being the optic nerve) that do not join with the brainstem.
    • The specialized olfactory receptor neurons of the olfactory nerve are located in the olfactory mucosa of the upper parts of the nasal cavity.
    • The olfactory nerves consist of a collection of many sensory nerve fibers that extend from the olfactory epithelium to the olfactory bulb, passing through the many openings of the cribriform plate of the ethmoid bone.

  • Oculomotor (III) Nerve

    • The oculomoter nerve (cranial nerve III) controls eye movement, such as constriction of the pupil and open eyelids.
    • The oculomotor nerve is the third paired cranial nerve.
    • Cranial nerves IV and VI also participate in control of eye movement.
    • Here the nerve is placed below the trochlear nerve and the frontal and lacrimal branches of the ophthalmic nerve, while the nasociliary nerve is placed between its two rami (the superior and inferior branch of oculomotor nerve).
    • Image of cranial nerves showing the position of the oculomotor 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.

  • Optic (II) Nerve

    • The optic nerve (cranial nerve II) receives visual information from photoreceptors in the retina and transmits it to the brain.
    • The optic nerve is also known as cranial nerve II.
    • Each human optic nerve contains between 770,000 and 1.7 million nerve fibers.
    • The optic nerve is the second of twelve paired cranial nerves.
    • As a consequence, optic nerve damage produces irreversible blindness.