hypoglossal nerve

Examples of hypoglossal nerve in the following topics:

• 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.
  • Proper function of the hypoglossal nerve is important for executing the tongue movements associated with speech.
  • Schematic image of the hypoglossal nerve and the structures it innervates.

• 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.

• Cervical Plexus

  • There is anastomosis with the accessory nerve, hypoglossal nerve, and sympathetic trunk.
  • The lesser occipital nerve, or small occipital nerve, is a cutaneous spinal nerve that arises between the second and third cervical vertebrae, along with the greater occipital nerve.
  • The great auricular nerve originates from the cervical plexus and is composed of branches from spinal nerves C2 and C3.
  • The supraclavicular nerves (descending branches) arise from the third and fourth cervical nerves.
  • The phrenic nerve (C3–C5, but primarily C4) is a nerve that originates in the neck and passes down between the lung and heart to reach the diaphragm.

• Medulla Oblongata

  • A stroke can injure the pyramidal tract, medial lemniscus, and the hypoglossal nucleus.
  • It is caused by an underlying collection of gray matter known as the spinal nucleus of the trigeminal nerve.
  • The gray matter of this nucleus is covered by a layer of nerve fibers that form the spinal tract of the trigeminal nerve.

• 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.