cranial nerve

Examples of cranial nerve in the following topics:

• 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.

• Brief Overview of Cranial Nerves

  • Cranial nerves are the nerves that emerge directly from the brain (including the brainstem).
  • The cranial nerves emerge from the central nervous system above this level.
  • Each cranial nerve is paired and is present on both sides.
  • The cranial nerves are considered components of the peripheral nervous system.
  • There are many mnemonic devices to remember the cranial nerves.

• 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).

• 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.

• 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.
  • The fibers that make up the accessory nerve enter the skull through the foramen magnum and proceed to exit the jugular foramen with cranial nerves IX and X.
  • However, more modern characterizations of the nerve regard the cranial component as separate and part of the vagus nerve.

• Sensory-Somatic Nervous System

  • Humans have 12 cranial nerves, nerves that emerge from or enter the skull (cranium), as opposed to the spinal nerves, which emerge from the vertebral column.
  • Each cranial nerve has a name .
  • Some cranial nerves transmit only sensory information.
  • Other cranial nerves transmit almost solely motor information.
  • Other cranial nerves contain a mix of sensory and motor fibers.

• 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.

• 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.

• 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.
  • Although it passes through the parotid gland, it does not innervate the gland (this is the responsibility of cranial nerve IX, the glossopharyngeal nerve).
  • Lower motor neuron lesions can result in a cranial nerve VII palsy (Bell's palsy is the idiopathic form of facial nerve palsy), manifested as both upper and lower facial weakness on the same side of the lesion.
  • Thus, the corneal reflex effectively tests the proper functioning of both cranial nerves V and VII.

• 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.