Cranial Nerves
The brainstem can be divided into three levels, the midbrain, the pons and the medulla. There are total 12 pairs of cranial nerves that originate from our brain and brain stem, see image.
Each cranial nerve carries different functions related to different senses of the body. Apart from sensory functions there are also some that work as motor nerves or mixed nerves.
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Locations of the Cranial Nerves
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| LOCATION |
NERVES |
Anterior of Brain
(Front of Brain) |
1, 2 |
| Midbrain |
3, 4 |
| Pons |
5, 6, 7, 8 |
| Medulla |
9, 10, 11, 12 |
Here is a brief description of the 12 cranial nerves.
1. Olfactory
This is a type of sensory nerve that contributes in the sense of smell in human beings. These basically provide the specific cells that are termed as olfactory epithelium. It carries the information from the nasal epithelium to the olfactory center in brain.
2. Optic
This is a type of sensory nerve that transforms information about vision to the brain. To be specific this supplies information to the retina in the form of ganglion cells.
3. Oculomoter
This is a form of motor nerve that supplies to different centers along the midbrain. Its functions include superiorly uplifting the eyelid, superiorly rotating the eyeball, construction of the pupil on the exposure to light and operating several eye muscles.
4. Trochlear
This motor nerve also supplies to the midbrain and performs the function of handling the eye muscles and turning the eye.
5. Trigeminal
This is a type of the largest cranial nerve in all and performs many sensory functions related to the nose, eyes, tongue and teeth. It basically is further divided in three branches that are ophthalmic, maxillary and mandibular nerve. This is a type of mixed nerve that performs sensory and motor functions in the brain.
6. Abducent
This is a type of motor nerve that supplies to the pons and performs the function of turning the eye laterally.
7. Facial
This motor nerve is responsible for different types of facial expressions. This also performs some functions of sensory nerve by supplying information about touch on the face and senses of tongue in mouth. It is basically present over the brain stem.
8. Vestibulocochlear
This motor nerve is basically functional in providing information related to balance of head and sense of sound or hearing. It carries vestibular as well as cochlear information to the brain and is placed near the inner ear.
9. Glossopharyngeal
This is a sensory nerve which carries sensory information from the pharynx (initial portion of throat) and some portion of tongue and palate. The information sent is about temperature, pressure and other related facts.
It also covers some portion of taste buds and salivary glands. The nerve also carries some motor functions such as helping in swallowing food.
10. Vagus
This is also a type of mixed nerve that carries both motor and sensory functions. This basically deals with the area of the pharynx, larynx, esophagus, trachea, bronchi, some portion of heart and palate. It works by constricting muscles of the above areas. In sensory part, it contributes in the tasting ability of the human being.
11. Spinal accessory
As the name intimates this motor nerve supplies information about the spinal cord, trapezius and other surrounding muscles. It also provides muscle movement of the shoulders and surrounding neck.
12. Hypoglossal
This is a typical motor nerve that deals with the muscles of tongue.
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