Cranial Nerves: Cranial nerves are pair of nerves that are arise from brain and have a sensory or motor function to different parts of head, neck and trunk.
There are 12 pairs of Cranial Nerves.
Each nerve are numbered according to Roman numeral between I to XII based on the location for from front to back of the brain.
Their functions are usually categorised as being either sensory or motor or both.
Sensory nerves are involved with transmission of impulse from body parts to the brain, such as smell, hearing and touch.
Motor nerves are involved with the transmission of impulse from the brain to different parts of the body such as control the movement and function of muscles and glands.
Cranial Nerves :
I. Olfactory Nerve II. Optic Nerve III. Occulomotor Nerve IV. Trochlear Nerve V. Trigeminal Nerve VI. Abducens Nerve VII. Facial Nerve VIII. Vestibulocochlear Nerve IX. Glossopharyngeal Nerve X. Vegus Nerve XI. Accessory Nerve XII. Hypoglossal Nerve
I. Olfactory Nerve
The olfactory nerve transmits sensory information to your brain regarding smells, which is located below the frontal lobe of the brain.
Nerve signals are then sent to areas of the brain concerned with memory and recognition of smells.
II. Optic Nerve :
The optic nerve, is the sensory nerve that involves in vision. When light enters in eye, it comes into contact with special receptors in the retina, called rods and cones.
Rods are found in large numbers and are highly sensitive to light. They’re more specialized for black and white or night vision.
Cones are present in smaller numbers. They have a lower light sensitivity than rods and are more involved with colour vision.
The information transmitted from retina to optic nerve and then both optic nerve). optic chiasm (meeting point of
III. Occulomotor Nerve :
The occulomotor has two different motor functions. – muscle function and pupil response.
Muscle function – Provides motor function to four out of six muscles around the eyes. These muscle helps the eyes to move and focus on objects.
Pupil response – It also helps to control the size of the pupil as it responds to light.
IV. Trochlear Nerve :
Controls the superior oblique muscle of the eyeball. This is the muscle, responsible for downward, outward and inward eye movements.
It emerges from the back part of midbrain.
V. Trigeminal Nerve :
The trigeminal nerve is the largest of all Cranial nerves and has both sensory and motor functions.
Trigeminal nerve has three divisions.
(i)Ophthalmic: Sends sensory information from the upper part of your face (forehead, scalp & upper eyelids).
(ii) Maxillary: Sends sensory information from the middle part of your face. (cheek, upper lip, nasal cavity).
(iii) Mandibular: Has both sensory & motor function. It sends sensory information from ears, lower lip & chin. And controls the movement of muscles within the jaw & ear.
VI. Abducens Nerve :
Controls the lateral rectus muscle of eye associated with eye movement. This muscle is involved in outward eye movement.
This nerve, also called the abducent nerve, starts in the pons region of the brainstem.
VII. Facial Nerve :
The facial nerve provides both sensory and motor function including-
(i) moving muscle, used for facial expressions.
(ii) Provide sense of taste for most part of tongue.
(iii) Supplying salivary glands and tear glands.
(iv) Sensation from the outer part of ear
It originates from the pons area of the brain stem.
VIII. Auditory / Vestibulocochlear Nerve :
Has sensory function involving hearing & balance
Consists of two parts – cochlear & vestibular portions
Cochlear portion – Specialized cells within your ear detect vibrations from sound based off of the sound’s loudness and pitch. This generates nerve impulse that are transmitted to the cochlear nerve.
Vestibular portion – Special cells track linear and rotational movements of the head. This information is transmitted to the vestibular nerve and used to adjust your balance and equilibrium.
The cochlear & vestibular portion of Vestibulo cochlear nerve originates in separate areas of the brain. The cochlear portion starts in cerebellar peduncle. The vestibular portion begins in pons and medulla.
IX. Glossopharyngeal Nerve :
Has both motor and sensory functions- Sending sensory information from sinuses, the back of throat, parts of inner ear, and the back part of the tongue.
Providing a sense of taste for the back part of tongue.
Stimulating voluntary movement of a muscle in the back of the throat called the stylopharyngeus.
The glossopharyngeal nerve originates in a part of your brainstem called the medulla oblongata.
X. Vegus Nerve :
The vagus nerve is a very diverse nerve. It has both sensory and motor functions, including
– Communicating sensation information from ear canal and parts of throat.
– Sending sensory information from organs in chest and trunk, such as heart and intestines.
– Allowing motor control of muscles in your throat.
– Stimulating the muscle of organs in chest and trunk, including those that move food through your digestive tract (peristalsis).
– Providing a sense of taste near the root of the tongue.
Out of all nerves, the Vagus nerve has the longest pathway. It originates in the medulla.
XI. Accessory Nerve :
Accessory nerve is a motor nerve that controls the muscle of the neck. These muscle allow to rotate flex, and extend the neck and shoulder.
lt’s divided into two parts – Spinal and Cranial. Spinal portion originates in the upper part of spinal cord and cranial portion starts is medulla oblongata.
XII. Hypoglossal Nerve :
Hypoglossal nerve is a motor nerve responsible for the movement of most of the muscle in tongue.
It starts in the medulla oblongata and moves down into the jaw, where it reaches the tongue.