mixed nerve

(noun)

Nerves that contain both afferent and efferent axons, and thus conduct both incoming sensory information and outgoing muscle commands in the same bundle.

Related Terms

Examples of mixed nerve in the following topics:

  • Overview of the Spinal Nerves

    • Spinal nerves, a part of the peripheral nervous system (PNS), are mixed nerves that send motor, sensory, and autonomic signals between the CNS and the body.
    • The term spinal nerve generally refers to a mixed spinal nerve that carries motor, sensory, and autonomic signals between the spinal cord and the body.
    • The posterior distribution of the cervical nerves includes the suboccipital nerve (C1), the greater occipital nerve (C2), and the third occipital nerve (C3).
    • The intercostal nerves come from thoracic nerves T1–T11, and run between the ribs.
    • The subcostal nerve comes from nerve T12, and runs below the twelfth rib.

  • 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.
    • Nerves can be further categorized based on where they connect to the central nervous system.
    • Cranial nerves innervate parts of the head and connect directly to the brain.
    • Cranial nerves are typically assigned Roman numerals from 0 to 12.

  • Function and Physiology of the Spinal Nerves

    • The term spinal nerve generally refers to a mixed spinal nerve, which carries motor, sensory, and autonomic signals between the spinal cord and the body.
    • The spinal nerve C1 (suboccipital nerve) provides motor innervation to muscles at the base of the skull.
    • These include the greater occipital nerve that provides sensation to the back of the head, the lesser occipital nerve that provides sensation to the area behind the ears, the greater auricular nerve, and the lesser auricular nerve.
    • 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.

  • 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.

  • 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.

  • 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.

  • Hypoglossal (XII) Nerve

    • The hypoglossal nerve (cranial nerve XII) controls the muscles of the tongue.
    • The hypoglossal nerve is the twelfth cranial nerve (XII) and innervates all extrinsic and intrinsic muscles of the tongue, except for the palatoglossus.
    • The hypoglossal nerve controls tongue movements of speech, food manipulation, and swallowing.
    • It supplies motor fibers to all of the muscles of the tongue, with the exception of the palatoglossus muscle, which is innervated by the vagus nerve (cranial nerve X) or, according to some classifications, by fibers from the glossopharyngeal nerve (cranial nerve IX) that hitchhike within the vagus.
    • Schematic image of the hypoglossal nerve and the structures it innervates.