About Cranial Nerves:
Cranial Nerves are an important part of the human body as these nerves take part in many of the things that we are able to do on our own such as seeing, eating, and the like. These nerves arise from the brain or brainstem and exist in pairs.
They supply blood and nourishment to various organs in the head and the neck areas except the vagus nerve which has a different function. There are 12 cranial nerves and majority of them carry sensory fibers but some cranial nerves carry motor fibers as well and some carry both sensory and motor fibers.
From the 12 cranial nerves, there are two nerves that arise from the cerebellum whereas the rest arise from the brainstem. These cranial nerves have been named based on their functions and structure. Delineated below are the list of the cranial nerves and their functions in detail.
List Of 12 Cranial Nerves & Their Functions
As stated above, there are 12 cranial nerves. These cranial nerves are:
As the name itself suggests that this nerve deals with the sense of smell. The receptors of these nerves are located in the nasal mucosa. This is the shortest nerve among all of the cranial nerves and it does not enter the brainstem.
Again as the name suggests, this nerve deals with vision and what we are able to see and not see. This nerve arises from the retina of the eye and sends visual signals to the brain which forms a picture of the object that we are seeing. This nerve is considered to be a part of the peripheral nervous system. Any damage or injury to this nerve can lead to complete loss of vision either temporarily or permanently depending on the injury caused to the nerve.
The Oculomotor Nerve comes third in the list of the 12 cranial nerves followed by the olfactory and the optic nerve. The function of this cranial nerve is to control eyeball and eyelid movement. This nerve has two motor component which have their own distinct functions and are somatic motor component and visceral motor component.
This is also known as Cranial Nerve IV and is the fourth in the list of cranial nerves. This is the only cranial nerve that arises dorsally from the brain. This nerve also provides its service to the eye. The main function of this nerve is to provide the ability to roll the eyes up and down and also outwards.
The trigeminal nerve is one of most important cranial nerves. It has three branches namely ophthalmic, maxillary, and mandibular. Each branch connects nerves from the brain to the different parts of the face. The main function of the trigeminal nerve is to provide sensations to mouth, teeth, face and the nasal cavity. This nerve also controls the nerve that allows us to chew food.
This nerve is also called as Cranial Nerve VI. The main function of this cranial nerve is to allow movement of the eyes sideways meaning away from the nose. Any injury to this nerve can result in an individual having blurred or double vision.
The facial nerve is also called as Cranial Nerve VII. It has namely two functions of which one is to carry sensory signals from the tongue to the interior portion of the mouth and secondly this nerve helps an individual produce facial expression.
As the name suggests, this cranial nerve has functions which include two parts of which first is the sense of hearing which is the cochlear part and the second is the ability of an individual to balance himself which forms the vestibular part. Any damage or injury to this cranial nerve may result in loss of hearing or balance issues with the affected individual.
The Glossopharyngeal Nerve is the ninth nerve of the 12 cranial nerves that are present in the body. This nerve starts from the brainstem and traverses through the base of the skull and terminates at the mouth in the mucous glands and base of the tongue.
This nerve has various branches which are the tonsillar branch, tympanic branch, stylopharyngeal branch, carotid sinus nerve branch, and lingual branch. Since it divides into many branches it has various functions.
It receives sensory fibers from the parts of the tongue, carotids, tonsils, and the middle ear. It also innervates the parasympathetic fibers which aid in digestion and resting the body. It also innervates the motor fibers of the stylopharyngeus muscle which aids in swallowing.
This cranial nerve forms a part of the involuntary nervous system and controls the body procedures which are not in the control of an individual like controlling the heart rate and aiding in food digestion. Stimulation of the vagus nerve is a preferred treatment for patients with epilepsy and depression.
Stimulation of the vagus nerve due to overreaction of the body to certain stimuli leads to a condition called vasovagal syncope or fainting episodes, as this stimulation causes a drop in blood pressure and heart rate.
This is the 11th cranial nerve of the 12 that exist in the human body. This nerve controls movement of the muscles of the neck. There are actually two parts of the Accessory Nerve which are the spinal and cranial divisions of which the cranial subdivision is disregarded. The spinal accessory nerve provides function to the sternocleidomastoid muscle, the upper back and the shoulder. Any dysfunction of this cranial nerve may lead to the shoulders and neck not performing to the desired level.
The Hypoglossal Nerve is the last of the cranial nerves. The main function of this cranial nerve is to control movements of the tongue. This nerve starts in the brainstem and traverses through the carotid artery and jugular vein and ends up beneath the tongue. Any damage or injury to the hypoglossal nerve may make the tongue completely paralyzed resulting in the individual not able to eat or speak properly. There are many numerous causes which can damage the hypoglossal nerve such as an infection or an injury to the nerve resulting in the tongue getting paralyzed.