Cranial nerves
Cranial Nerves

12 Cranial Nerves: Definition and Functions

Behind our ability to recognize a person’s face or smell food, there are nerves that play a role.

Cranial Nerves Definition

Cranial nerve is a retirement that serves to initiate motorists or receive stimuli from sensory in the face. As is well known, there are 12 cranial nerves, commonly written in Roman numerals.

The cranial nerve is part of the conscious nervous system, located near the central nervous system of the cranium/skull. These nerves are connected to the structures present in the human head and neck. There are 12 pairs of cranial nerves coming from our brains and brainstems. Each has different functions related to a different understanding of the body.

The twelve pairs of cranial nerves are always numbered using Roman numerals. Some cranial nerves I, II, and VIII contain only sensory fibers; while almost of them contains motor fibers; The rest of V, VII, IX, X contains both sensory and motor fibers known as mixed nerves.

Cranial Nerves Functions

The head is the control center of our body. In addition to the brain, the head is also the center of the nervous system in addition to the spine. The group of nerves sourced from the head, referred to as the cranial nerve.

I. Olfactory nerve.

It is the olfactory nerve that plays a role in smell. These nerves send information from the nose to the brain about the smells that are around us. So, if you accidentally smell instant noodles, then your olfactory nerves are at work.

II. Optic nerve

These second-order nerves play a role in sending vision information from the retina to the eye.

III. Oculomotor nerve

  • Nerves that serve to supply nerves to the muscles around the eye, including the upper eyelid muscles (making the eyelids move), extraocular muscles, and pupil muscles (making the pupils shrink).
  • How to Check: Eyeball rotation test, moving conjunctiva, pupil reflex and eyelid inspection.

IV. Trochlear nerve

The nerve that controls the superior auditory muscle of the eye, which is one of the muscles that moves the eye and is the muscle outside the eyeball (extraocular muscle). Paralyzed trochlear nerves can cause the eyeball to rotate upwards and outwards, resulting in a double view.

V. Trigeminal Nerve.

  • Functions: motor nerve, motion, facial sensation, tongue and teeth, corneal reflex and blink reflex
  • How to Test: move the jaws all sides, the patient closes the eyes, touches with a cotton swab on the forehead or cheeks, touch the surface of the cornea with a cotton swab.

VI. Abducens nerve.

  • Function: motor nerve, lateral eye deviation
  • How to check: same as nerve III.

VII. Facial Nerve.

  • Function: motor nerve, for facial expressions
  • How to check: smile, whistle, raise eyebrows, close eyelids with resistance, stick out tongue to distinguish sugar and salt.

VIII. Vestibulocochlear nerve

This nerve consists of sensory nerves and has two branches, namely:

  • The cochlear or auditory branch serves to convey information from the receptors for the auditory senses in the inner ear cortiary organ to the cochlear nuclei in the medulla, to the inferior colliculus, to the medial geniculate nucleus of the thalamus and then to the auditory area of the temporal lobe.
  • The vestibular branch carries information relating to equilibrium and the orientation of the head to the space received from sensory receptors in the inner ear.

The functions of these nerves are:

  • A sensory vestibular system to control the balance of the body.
  • Sensory cochlear to receive stimuli from the ear to be processed in the brain as sound.

IX. Glossopharyngeal nerve

The next 12 cranial nerves are glossopharyngeal nerves having a role in motor as well as sensory functions. In this nerve is related to the tongue, throat, as well as one of the salivary glands that is the parotid gland.

X. Vagus nerve

The type of nerve combined with the sensory part plays a role in feeling the sensation of the outer ear, throat, heart, and abdominal organs. The inner muscles support the movement of the throat and soft palate. 

XI. Accessory nerve

These nerves function in supporting the motor of the movement of the neck muscles. Which controls the neck muscles so that humans are able to move the neck muscles as desired.

XII. Hypoglossal nerve

The main function of these hypoglossal nerve is to move the tongue muscles or motor functions.

This nerve examination method: the doctor will ask you to stick out your tongue and move it from one side to the other.


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Last Updated on March 29, 2021 Reviewed by Market Health Beauty Team


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