What are Cranial Nerves?
“Nerves that extend throughout the body on both sides emerging directly from brain and brain stem are called cranial nerves.”
Cranial nerves carry information from the brain to all parts of the body, primarily to the head and neck. These nerves are paired and present on both sides of the body. They are mainly responsible for facilitating smell, vision, hearing, and movement of muscles.
Cranial nerves are concerned with the head, neck, and other facial regions of the body. Cranial nerves arise directly from the brain in contrast to spinal nerves and exit through its foramina. Most of the cranial nerves originate in the brainstem and pass through the muscles and sense organs of head and neck.
Traditionally, there are twelve cranial nerves which are numbered using roman numerals according to the order in which they emerge from the brain (from front to back).
Cranial nerves are considered as a part of the peripheral nervous system, although olfactory and optic nerves are considered to be part of the Central nervous system. Most of the cranial nerves belong to the somatic system. Some of the cranial nerves are responsible for sensory and motor functions as they contain only sensory fibres and motor fibres. Others are mixed nerves because they include both sensory and motor fibres.
Only cranial nerves I and II are purely sensory and are responsible for the sense of smell and vision (optic nerve II). The rest of the cranial nerves contain both afferent and efferent fibres and are therefore referred to as the mixed cranial nerves. However, the vagus nerve has branches to most of the internal organs and is the part of the autonomic nervous system.
Also Read: Nerves
Learn about different cranial nerves and their functions by referring to the cranial nerves list given in this article.
Cranial Nerves List
Cranial nerves are basically named according to their structure and functions. Olfactory and optic nerves emerge from the cerebrum and all other 10 nerves emerge from the brain stem. Cranial nerve functions include all five senses and muscle movements.
The below table provides the list of cranial nerves along with their location and functions.
|Cranial Nerves List||Location||Type||Function|
|Olfactory (I)||Cribriform plate||Sensory||Smell|
|Optic (II)||Optic foramen||Sensory||Vision|
|Oculomotor (III)||Superior orbital fissure||Motor||Eye movement|
|Trochlear (IV)||Superior orbital fissure||Motor||Eye movement|
|Trigeminal (V)||Superior orbital fissure||Mixed||Facial sensation|
|Abducens (VI)||Superior orbital fissure||Motor||Eye movement|
|Facial (VII)||Internal auditory canal||Mixed||Facial expression|
|Vestibulocochlear nerve (VIII) (auditory vestibular nerve)||Internal auditory canal||Sensory||Hearing and balance|
|Glossopharyngeal (XI)||Jugular foramen||Mixed||Oral sensation and taste|
|Vagus (X)||Jugular foramen||Sensory||Vagus nerve|
|Accessory (XI)||Jugular foramen||Motor||Shoulder elevation and head-turning|
|Hypoglossal (XII)||Hypoglossal||Motor||Tongue movement|
Functions of Cranial Nerves
Following is the cranial nerves list along with the important functions they perform:
Olfactory nerve: This nerve helps to feel the sense of smell. This is the primary nerve that is responsible for the smell. Damage to this nerve may result in distortion of smell and taste.
Optic nerve: The optic nerve II is the agent of vision. This transmits visual information from eyes to the brain and vice versa. Any damage to this nerve results in problems related to sight and vision.
Oculomotor nerve: Oculomotor nerve helps in the movement of the eye. Damage to this nerve leads to distortion in vision or double vision and even problem in the coordination of eyes.
Trochlear and Abducens nerves: These nerves also help in eye movement. Damage to the Trochlear nerve might cause inability to move eyeball downwards and damage to abducens nerve might result in diplopia.
Trigeminal nerve: This nerve helps you to have facial sensation. This nerve comprises of three parts namely ophthalmic, maxillary and mandibular.
Facial nerve: This nerve is responsible for facial expression. Due to the damage to this nerve, it might cause the inability to move face parts on one or more sides.
Vestibulocochlear nerve (auditory vestibular nerve): Vestibulocochlear (auditory vestibular nerve) is responsible for hearing and balance. This helps eyes to keep track of moving objects while your head is stable. The sensation of spinning and dizziness are the symptoms of damage to this nerve. This nerve branches into the vestibular nerve and cochlear nerve.
Glossopharyngeal: Oral sensation and sense of taste are stimulated by this nerve. Damage to this nerve disables the sense of taste.
Vagus nerve: This nerve monitors the level of oxygen and helps us to feel the sensation of heat or cold near the throat area. Damage to this nerve leads to the inability to swallow. Major damage to the vagus nerve might result in hypertension or high blood pressure and heart attack.
Accessory nerve: This nerve is also known as nerve XI and arises from two roots namely the cranial and spinal bones. This nerve controls swallowing movements and helps in the movement of head and shoulders.
Hypoglossal nerve: This nerve facilitates the movement of the tongue and helps to talk, swallowing etc.
Read more about Nervous System Diseases
The cranial nerves list gives a brief insight into the functions of cranial nerves. To know more about cranial nerves and other Biology topics, keep visiting BYJU’S website.
Frequently Asked Questions
How many cranial nerves are there in human body?
There are 12 cranial nerves in the human body. Olfactory nerve, optic nerve, facial nerve, oculomotor nerve, vagus nerve, hypoglossal, nerve, vestibulocochlear nerve, accessory nerve, trochlear nerve, glossopharyngeal nerve, trigeminal nerve and abducens nerve.
What is the purpose of cranial nerves in human body?
The cranial nerves carry information from brain to all parts of the body and facilitate the sense of vision, smell, muscle movement and hearing.
How are cranial nerves different from spinal nerves?
The cranial nerves emerge directly from the brain and brain stem. On the contrary, the spinal nerves emerge from the segments in the spinal cord. The cranial nerves transmit information between brain and human body. Whereas, the spinal nerves carry signals from the spinal cord to the body.
What is a spinal nerve?
A spinal nerve is a mixed nerve that transmits sensory, motor or autonomic signals between the spinal cord to the body. There are 31 pairs of spinal nerves in the human body.
What is the function of the optic nerve?
The optic nerve relays signals between the brain and the eyes and acts as the agent of vision.
What happens if the vestibulocochlear nerve gets damaged?
If the vestibulocochlear nerve gets damaged it results in dizziness and spinning.
What is an accessory nerve?
The accessory nerve is the cranial nerve that arises from the cranial and the spinal bones and is responsible for controlling the swallowing and the movement of head and shoulders.