Function of the cranial nerves | Brain Nerves

Function of the cranial nerves

What exactly do the brain nerves actually do, why do we need them? In short: They conduct the sensations of our sense organs, i.e. what we see (II), hear (VIII), taste (VII, IX, X), smell (I), feel in the area of the head (V), information of our sense of balance (VIII), information about the blood pressure in large cervical arteries (IX and X from the glomus caroticum) etc. directly into our brain for further processing.

In addition, they transmit commands from the brain to a variety of muscles, including the eye muscles (III, IV, VI), the masticatory muscles (V), the facial mimic muscles (VII), the pharyngeal muscles (IX, X), the muscles of the larynx (X), some neck muscles (XI) and the tongue muscles (IX, XII). In addition to muscles, glands are also controlled, e.g. the lacrimal gland and salivary glands as well as numerous reflexes such as the swallowing reflex or eyelid closure reflex (corneal reflex). Only the X.

Only the X. cranial nerve, the vagus nerve, supplies areas of our body that extend far beyond the head and neck area, such as all organs of the chest and abdominal cavity. This shortened list already shows how important our 12 cranial nerves really are. Cranial nerve I: Olfactory nerve (also olfactory nerve) Cranial nerve II: Optic nerve (also optic nerve) Cranial nerve III: Oculomotor nerve Cranial nerve IV: Trochlear nerve Cranial nerve V: Trigeminal nerve (also triplet nerve) Cranial nerve VI: Cranial nerve IX: Glossopharyngeal nerve Cranial nerve X: Vagus nerve Cranial nerve XI: Accessorius nerve XII: Hypoglossal nerve

  • Main function: Mediates olfactory sensations to the brain (see nose)
  • Common diseases/failure: The inability to smell (anosmia) or an attenuation (hyposmia).

    Frequently with anterior skull base fractures.

  • Main function: conveys the images taken by the eye to the brain
  • Common diseases/failure: loss of visual field, dark spots, hemianopsia, quadrant anopia, blinker phenomenon, etc.Even with high pressure inside the skull: “congestion papilla” (see vision; visual path)
  • Main function: Controls eye movements as well as all internal eye muscles (e.g. ciliary muscle) and the width of the pupil
  • Frequent illness/failure: Unequal dilated pupils (anisocoria), narrow pupils (miosis), dilated pupils (mydriasis) Eye paralysis, the eye looks outwards and downwards, therefore double images possible. Problems with “focusing” of what you see (accommodation disorders). Drooping upper eyelid (ptosis).
  • Main function: Controls a specific eye muscle
  • Common diseases/failure: Eye looks towards the nose and upwards, also double images
  • Main function: Consists of 3 strong nerve branches, hence the name triplet nerve.

    It conducts sensitive information from the head area to the brain and innervates, among other things, the chewing muscles

  • Frequent diseases/failure: Rare failure of the entire nerve, rather individual branches fail. Then sensitivity disorders of the head (peripheral or central type). When opening the mouth, the lower jaw moves towards the “sick side”.

    Painful hypersensitivity of the nerve (trigeminal neuralgia) without an identifiable cause or also in the case of sinusitis. Loss of corneal reflex, rarely hearing difficulties (hypacusis)

  • Main function: Innervates a specific eye muscle
  • Frequent diseases/failure: Eye looks towards the nose, double images. Often in pathological processes at the sinus cavernosus first visible at VI
  • Main function: Controls among other things the musculature of the mimic, mediates the taste perception in the front parts of the tongue and innervates a multiplicity at glands in the head range
  • Common diseases/failure: Paralysis of the facial muscles (difference between central and peripheral facial paresis).

    Sounds are heard too loud (hyperacusis), loss of taste sensation on the front tongue, burning eyes due to drying of the conjunctiva/cornea (see conjunctivitis)

  • Main function: Mediates the sense of hearing and balance from the inner ear to the brain (see ear)
  • Common illnesses/failure: hearing loss, deafness, disturbance in spatial orientation, gaze stabilization and posture. Furthermore dizziness, nausea, falling tendency and twitching of the eye (nystagmus)
  • Main function: Directs the taste sensation of the back part of the tongue to the brain and innervates many muscles of the throat and parts of its sensitivity, also important for the movement of the tongue. Essential for the swallowing reflex.

    Also innervates the largest salivary gland on the head

  • Common illnesses/failure: loss of gag reflex, problems with swallowing and drinking, uvula deviates to the healthy side. Loss of taste in the back part of the tongue (especially for the sensation “bitter”). Nasal sounding speech
  • Main function: Conducts taste sensations from the throat area to the brain, completely supplies the larynx (sensitive and motoric).

    Is a significant part of the vegetative nervous system and embodies the “parasympathetic nervous system” far into the abdominal area. It also regulates the heart rate, the secretion of gastric acid, the movement of the intestines and numerous other functions of internal organs

  • Common Diseases/Failure: Hoarseness when a certain branch (laryngeal recurrens nerve) becomes pinched due to lung cancer (bronchial carcinoma) or aortic aneurysm or thyroid surgery Concerning the swallowing and the uvula, as in IX, everything is possible. Severe shortness of breath if a certain muscle of the larynx fails (posticus paralysis), change in heart rate (faster and slower possible), less stomach acid and intestinal movements etc.

    possible

  • Main function: Supplies proportionally 2 important muscles of the neck/neck. Actually the effective fibers of XI originate from the cervical spinal cord, the name cranial nerve is derived from other peculiarities
  • Frequent diseases/failure: Often damage after ENT surgery or lymph node removal from the neck. Then the head is tilted to the opposite side of the injury and the head is turned to the same side of the injury. Weakness when lifting the arm
  • Main function: Supplies a variety of muscles on the tongue
  • Frequent illnesses/failure: Tongue deviates when stretched out to the sick side. Speech disorders and difficulty swallowing

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All articles in this series:

  1. Brain Nerves
  2. Function of the cranial nerves
  3. Common diseases