What are cranial nerves?
cranial nerves are pairs of nerves that connect your brain to several parts of your head, neck, and trunk. There are 12 of them, each named according to their function or structure.
Each nerve as well has a corresponding Roman numeral between I and XII. This is based on their location from front to back. Example , the olfactory nerve is nearest to the front of the head, so it’s designated as I.
Their functions are usually characterized as being either sensory or motor. Sensory nerves are involved with sensory perception , such as smell, hearing, and touch. Motor nerves cordinates the movement and funsubsceptibilityes or glands.
Below are the cranial nerves and their functions
I. Olfactory nerve
The olfactory nervet ransmits sensory details to your brain regarding smells that you encounter.
When you inhale or breath in aromatic molecules, they dissolve in a moist lining at the roof of your nasal cavity, called the olfactory epithelium. This activates receptors that produces nerve impulses that go to your olfactory bulb. Your olfactory bulb is an oval-shaped structure that houses specialized groups of nerve cells.
From the olfactory bulb, nerves passes into your olfactory tract, which is placed below the frontal lobe of your brain. Nerve signals are then transmitted to areas of your brain concerned with memory and recognition of smells.
II. Optic nerve
The optic nerve is the sensory nerve that involves vision.
When light enters into your eye, it comes into contact with special receptors in your retina called rods and cones. Rods are found in large numbers and are highly susceptible to light. They’re more specialized for black and white or night vision.
Cones are present in smaller numbers. They have a lower light susceptibility than that of rods and are more involved with color vision.
The information received by your rods and cones is transferred from your retina to your optic nerve. Once inside your skull, both of your optic nerves come to together to form the optic chiasm. At the optic chiasm, nerve fibers from half of each retina form two separate optic tracts.
Through each of the optic tract, the nerve impulses inevitably reach your visual cortex, which then processes the information. Your visual cortex is placed in the back part of your brain.
III. Oculomotor nerve
The oculomotor nerve has two separate motor functions: muscle function and pupil response.
In Muscle function. Your oculomotor nerve gives motor function to the four of the six muscles around your eyes. These muscles help your eyes move and focus on an objects.
In Pupil response. It helps to control the size of your pupil as it responds to light.
This nerve initiates in the front part of your midbrain, which is a part of your brainstem. It moves forward from that point until it reaches the area of your eye sockets.
IV. Trochlear nerve
The trochlear nerve controls your superior oblique muscle. This is the muscle that’s responsible for downward, outward, and inward eye movements.
It stems from the back part of your midbrain. Like your oculomotor nerve, it moves forward until it gets to your eye sockets, where it activates the superior oblique muscle.
V. Trigeminal nerve
The trigeminal nerve is the largest of your cranial nerves and has both sensory and motor functions.
The trigeminal nerve has three divisions, which are:
Ophthalmic. The ophthalmic division transmits sensory information from the upper part of your face, including your forehead, scalp, and upper eyelids.
Maxillary. This division impart sensory information from the middle part of your face, including your cheeks, upper lip, and nasal cavity.
Mandibular. The mandibular division has both a sensory and a motor function. It sends sensory information from your ears, lower lip, and chin. It also takes care of the movement of muscles within your jaw and ear.
The trigeminal nerve initiates from a group of nuclei — which is a collection of nerve cells — in the midbrain and medulla regions of your brainstem. Eventually, these nuclei form a different sensory root and motor root.
The sensory root of your trigeminal nerve branches into the ophthalmic, maxillary, and mandibular divisions. The motor root of your trigeminal nerve goes below the sensory root and is only distributed into the mandibular division.
VI. Abducens nerve
The abducens nerve controls another muscle that’s associated with eye movement, called the lateral rectus muscle. This muscle is involved in outward eye movement. For instance, you will use it to look to the side.
This nerve, also called the abducent nerve, begins in the pons region of your brainstem. It eventually enters your eye socket, where it controls the lateral rectus muscle.
VII. Facial nerve
The facial nerve provides both sensory and motor functions, including:
moving muscles used for facial expressions as well as some muscles in your jaw
providing a sense of taste for most of your tongue
supplying a glands in your head or neck area, such as salivary glands and tear-producing glands
Imparting sensations from the outer parts of your ear
Your facial nerve has a very complex path. It place in the pons area of your brainstem, where it has both the motor and the sensory root. Eventually, the two nerves converge together to form the facial nerve.
Both within and outside of your skull, the facial nerve branches grows into smaller nerve fibers that stimulate muscles and glands or provide sensory information.
VIII. Vestibulocochlear nerve
Your vestibulocochlear nerve has sensory work involving hearing and balance. It consists of two parts, the cochlear portion and vestibular portion:
Cochlear portion. Specialized cells within your ear detect vibrations from sound based on sound loudness and pitch. This produces nerve impulses that are tranferred to the cochlear nerve.
Vestibular portion. Another set of special cells in this portion can track both the linear and the rotational movements of your head. This information is transferred to the vestibular nerve and used to improve your balance and equilibrium.
The cochlear and the vestibular portions of your vestibulocochlear nerve place in separate areas of the brain.
The cochlear portion begins in an area of your brain called the inferior cerebellar peduncle. The vestibular portion begins in your pons and medulla. Both areas combine to form the vestibulocochlear nerve.
IX. Glossopharyngeal nerve
The glossopharyngeal nerve has both the motor and the sensory functions, including:
Sending sensory knowledge from your sinuses, the back of your throat, parts of your inner ear, and the back part of your tongue
Preparing a sense of taste for the back part of your tongue