Your cranial nerves are pairs of nerves that connect your brain to various parts of your head, neck, and torso. There are 12 of them, each named according to their function or structure.
Their functions are usually categorized as sensory or motor. Sensory nerves are connected to your senses like smell, hearing, and touch. Motor nerves control the movement and function of muscles or glands.
Read on to learn more about each of the 12 cranial nerves and their function.
The cranial nerves are located in the skull, at the bottom of the brain. They start in the nuclei of the brain and travel various pathways to control your senses and movements.
Each nerve has a corresponding Roman numeral between I and XII. This is based on their front to back position. For example, your olfactory nerve is closest to the front of your head, so it's called the I.
Cranial nerve conditions and disorders can affect processes involving vision, smell, hearing, speech, and balance. They can also change the way you experience facial sensation and prevent or change the movement of your head, eyes, neck, shoulders, throat and tongue.
Cranial nerve palsy affects a motor nerve — one that controls movement.
When a sensory nerve is affected, it can cause pain or reduced sensation.
Conditions and disorders affecting the cranial nerves may include:
- Third nerve palsy.This disorder can cause a closed or partially closed eyelid, an enlarged pupil, and outward and downward movement of the eye.
- Trigeminusneuralgie. Trigeminusneuralgieis a disease of the fifth cranial nerve and typically causes pain on one side of the face.
- Fourth nerve palsy or superior oblique nerve palsy.This disorder can cause misalignment of the eyes and affect one or both eyes.
- Sixth nerve palsy or abductor palsy.This type of paralysis can cause the eye to wander inward toward the nose.
- Bell's palsy.Bell's palsy, a disorder of the seventh cranial nerve, can cause temporary weakness or paralysis on one side of the face.
- Hemifacial spasm.AHemifacial spasmoccurs when blood vessels narrow the seventh cranial nerve, causing a facial spasm or tic.
- Glossopharynxneuralgie.This condition affects the ninth cranial nerve and can cause pain at the base of the tongue that can travel to the ear and throat.
- skull base tumors.These are tumors that form in the skull and can affect various cranial nerves.
Injuries, trauma etcwhiplashcan also damage cranial nerves.
Disorders affecting the cranial nerve can cause different symptoms depending on which nerve is affected.
If you experience facial pain, a change in your ability to change the movements of your head or eyes, or changes in perception related to vision, hearing, smell, balance or speech, you may have a cranial nerve disorder.
Symptoms of cranial nerve damage can include:
- Pain in the face, tongue, head or neck
- inability to focus the eye
- an eye that drifts sideways or down
- weakness or paralysis in the face
- slurred speech
- vision or hearing loss
- changes in vision
Thatolfactory nervesends sensory information to your brain about smells you encounter.
When you inhale molecules with a scent, known as aromatic molecules, they dissolve into a moist lining at the roof of your nasal cavity.
This lining is called the olfactory epithelium. It stimulates receptors that create nerve impulses that travel to your olfactory bulb. Your olfactory bulb is an oval structure that contains specialized clusters of nerve cells.
From the olfactory bulb, nerves go into your olfactory tract, which is located under the olfactory tractfrontal lobes of your brain. Nerve signals are then sent to areas of your brain involved in memory and smell recognition.
II. optic nerve
Thatoptic nerveis the sensory nerve that affects vision.
When light enters your eye, it comes into contact with special receptors in your eyeRetinacalled rods and cones. Rods are plentiful and very sensitive to light. They are more specialized in black and white or night vision.
There are fewer cones. They are less sensitive to light than rods and are more involved in color vision.
The information received by your rods and cones is sent from your retina to your optic nerve. Once inside your skull, your two optic nerves meet to form something called theoptic chiasm. At the optic nerve cross, nerve fibers from half of each retina form two separate visual pathways.
Eventually, through each visual tract, nerve impulses reach your visual cortex, which then processes the information. Your visual cortex is located at the back of your brain.
III. Motor Nerv
Thatoculomotor nervehas two distinct motor functions: muscle function and pupillary response.
- Muscle function.Your oculomotor nerve supplies motor function to four of the six muscles around your eyes. These muscles help your eyes move and focus on objects.
- student response.It also helps control the size of your pupil as it responds to light.
This nerve originates in the front of your midbrain, which is part of your brainstem. It moves forward from this area until it reaches the area of your eye sockets.
IV. Full of nerve
Thatlearn nervescontrols yoursuperior oblique muscle. This is the muscle responsible for downward, outward, and inward eye movements.
It exits from the back of your midbrain. Like your oculomotor nerve, it moves forward until it reaches your eye sockets, where it stimulates the superior oblique muscle.
V. Trigeminal nerve
Thattrigeminalis the largest of your cranial nerves and has both sensory and motor functions.
The trigeminal nerve has three divisions, which are:
- Ophthalmisch.The ophthalmology department sends sensory information from the top part of your face, including your forehead, scalp, and upper eyelids.
- Upper jaw.This department communicates sensory information from the middle part of your face, including your cheeks, upper lip, and nasal cavity.
- lower jaw.The lower jaw area has both a sensory and a motor function. It sends sensory information from your ears, lower lip, and chin. It also controls the movement of the muscles in your jaw and ear.
The trigeminal nerve originates from a group of nuclei — a collection of nerve cells — in the midbrain and medulla regions of your brainstem. Finally, these nuclei form a separate sensory root and motor root.
The sensory root of your trigeminal nerve branches into the ocular, maxillary, and mandibular departments.
The motor root of your trigeminal nerve runs below the sensory root and connects only to the mandibular division.
6. Kidnap nerves
Thatkidnap nervescontrols another muscle associated with eye movement, called theM. rectus lateralis. This muscle is involved in outward eye movement. For example you would use it to look to the side.
This nerve, also called the abducens nerve, begins in theponsregion of your brainstem. It eventually enters your eye socket, where it controls the lateral rectus muscle.
VII. facial nerve
Thatfacial nerveprovides both sensory and motor functions, including:
- movable muscles used for facial expressions, as well as some muscles in your jaw
- Providing a sense of taste for most of your tongue
- supplying glands in the head or neck area, such as salivary glands and lacrimal glands
- Sending sensations from the outer parts of your ear
Your facial nerve has a very complex pathway. It originates in the pons area of your brainstem, where it has both a motor and sensory root. Eventually, the two nerves fuse together and form the facial nerve.
Both inside and outside your skull, the facial nerve further branches into smaller nerve fibers that stimulate muscles and glands or provide sensory information.
VIII. Vestibulocochlear Nerv
YourVestibulocochlear nervehas sensory functions involving hearing and balance. It consists of two parts, the cochlear part and the vestibular part:
- Cochlea-Teil.Specialized cells in your ear detect vibrations from sound based on the volume and pitch of the sound. This creates nerve impulses that are sent to the cochlear nerve.
- vestibular part.Another set of special cells in this section can track both linear and rotational movements of your head. This information is relayed to the vestibular nerve and used to adjust your balance and balance.
The cochlear and vestibular parts of your vestibulocochlear nerve originate from separate areas of the brain.
The cochlear portion begins in an area of your brain called the lower cerebellar peduncle. The vestibular part starts in your pons and medulla. Both parts together form the vestibulocochlear nerve.
IX. Nervus glossopharyngeus
ThatNervus glossopharyngeushas both motor and sensory functions, including:
- Sending sensory information from your sinuses, the back of your throat, parts of your inner ear, and the back of your tongue
- Providing a sense of taste to the back of your tongue
- Stimulating voluntary movement of a muscle in the throat called the stylopharyngeus
The glossopharyngeal nerve originates in a part of your brainstem known as the Nelongated medulla. It eventually extends into your neck and throat region.
X. Vagus nerve
ThatVagus nerveis a very diverse nerve. It has both sensory and motor functions, including:
- Transmission of sensory information from your ear canal and parts of your throat
- Sending sensory information from organs in the chest and trunk, such as the heart and intestines
- allows motor control of the muscles in your neck
- Stimulate the muscles of the organs in your chest and trunk, including those that move food through your digestive tract
- Providing a sense of taste near the root of the tongue
Of all the cranial nerves, the vagus nerve has the longest pathway. It extends from the head to the abdomen. It originates in the part of your brainstem called the medulla.
XI. accessory nerve
Youraccessory nerveis a motor nerve that controls the muscles in your neck. These muscles allow you to rotate, flex, and straighten your neck and shoulders.
It is divided into two parts: spinal and cranial. The spinal portion originates in the upper part of your spinal cord. The cranial portion begins in your medulla oblongata.
These parts meet briefly before the spinal part of the nerve moves to supply the neck muscles. The cranial part follows the vagus nerve.
XII. Hypoglossal nerve
YourNervus hypoglossusis the 12th cranial nerve. It is responsible for the movement of most of the muscles in your tongue.
It begins in the medulla oblongata and moves down into the jaw where it reaches the tongue.
You can help keep your cranial nerves healthy by following practices that keep your body, cardiovascular system, and central nervous system healthy.
According to that
- get around
7 to 9 hourssleep quality every night
- do not smoke, or if you smoke,stop smokingif possible
- treatDiabetes, if you have it
- treathigh blood pressure, if you have it
- food aheart healthy dietand aim to keep your low-density lipoprotein (LDL) cholesterol in a healthy range
- to getregular training
Explore this interactive 3D diagram below to learn more about the 12 cranial nerves.
Your brain has 12 cranial nerves involved in your sensory, motor, and autonomic functions. They are in your skull at the bottom of your brain. They are numbered according to their location.
Olfactory nerve (CN I), optic nerve (CN II), oculomotor nerve (CN III), trochlear nerve (CN IV), trigeminal nerve (CN V), abducens nerve (CN VI), facial nerve (CN VII), vestibulocochlear nerve (CN VIII), glossopharyngeal nerve (CN IX), vagus nerve (CN X), accessory nerve (CN XI), and hypoglossal nerve (CN XII).What are the 12 cranial nerves names? ›
There are 12 pairs of cranial nerves in the human body. The 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.Where are the 12 cranial nerves located in the brain? ›
The cranial nerves are located within the skull, on the underside of the brain. They begin in the nuclei of the brain and travel different paths to help control your senses and movement. Each nerve has a corresponding Roman numeral between I and XII.What are the 12 pairs of cranial nerves and their functions quizlet? ›
- Olfactory. Sense of smell.
- Optic. Sense of Sight.
- Oculomotor. Eye movement (including constriction of pupil)
- Trochlear Nerve. Eye movement (up, down, side to side)
- Trigeminal Nerve. Facial Sensations/Chewing muscles.
- Abducens. Eye movement.
- Facial Nerve. Facial Expressions/Sense of Taste.
The nerves can be either be sensory (S), motor(M) or both(B). So we use S, M and B for our mnemonics. Depending on their type, the initial letters that we get are 'SSMMBMBSBBMM'. Another commonly used Mnemonic is 'Some Say Money Matters, But My Brother Says Bakes Brownies Matter Most'.What is a 12 cranial nerve assessment? ›
The 12th (hypoglossal) cranial nerve is evaluated by asking the patient to extend the tongue and inspecting it for atrophy, fasciculations, and weakness (deviation is toward the side of a lesion).What are the 12 cranial nerves by Roman numerals? ›
Cranial nerves are designated by Roman numerals, as follows: I, olfactory nerve; II, optic nerve; III, oculomotor nerve; IV, trochlear nerve; V, trigeminal nerve; VI, abducens nerve; VII, facial nerve; VIII, vestibulocochlear nerve; IX, glossopharyngeal nerve; X, vagus nerve; XI, accessory nerve; and XII, hypoglossal ...What is the best assessing cranial nerve 12? ›
The 12th (hypoglossal) cranial nerve is evaluated by asking the patient to extend the tongue and inspecting it for atrophy, fasciculations, and weakness (deviation is toward the side of a lesion).What happens if cranial nerve 12 is damaged? ›
Disorders of the 12th cranial nerve (hypoglossal nerve) cause weakness or wasting (atrophy) of the tongue on the affected side. This nerve moves the tongue. Hypoglossal nerve disorders may be caused by tumors, strokes, infections, injuries, or amyotrophic lateral sclerosis.Are the 12 cranial nerves motor or sensory? ›
Cranial nerves I, II, and VIII are pure sensory nerves. Cranial nerves III, IV, VI, XI, and XII are pure motor nerves.
- Old: Olfactory.
- Operators: Optic.
- Occasionally: Oculomotor.
- Troubleshoot: Trochlear.
- Tricky: Trigeminal.
- Abducted: Abducens.
- Family: Facial.
- Veterans: Vestibulocochlear.
Hypoglossal nerve This nerve controls the movement of the tongue which is important for speech and swallowing.Which cranial nerve is the vagus nerve? ›
These fibers send information between your brain, heart and digestive system. The vagus nerves are the 10th of 12 cranial nerves. The vagus is known as cranial nerve X, the Roman numeral for 10.Why are cranial nerves named and numbered? ›
The numbering of the cranial nerves is based on the order in which they emerge from the brain and brainstem, from front to back. The terminal nerves (0), olfactory nerves (I) and optic nerves (II) emerge from the cerebrum, and the remaining ten pairs arise from the brainstem, which is the lower part of the brain.