Cranial nerves are those nerves that emerge from the brain stem. There are thirteen nerves in the human body that originate from the brain but only twelve of them are classified as cranial nerves. These nerves starting from the third one begin from the brain stem but the tenth and eleventh nerves are not included in this category as they are predominantly involved in the motor and sensory system for the head and the neck region.

Cranial nerves are different from peripheral nerves and are divided in such as way that they are capable of performing specific functions in the extensive anatomical regions, whereas the peripheral nerves are divided in such a way that segmental innervations can be achieved.

Names of Nerves:

The twelve pairs of the cranial nerves have been conventionally abbreviated using Roman numerals; the nerves are given a specific number depending on the location of their nuclei in the brain stem.

0. Cranial nerve zero is a non recognized cranial nerve which is sensory in nature and the functioning of this nerve is still in question. However, contemporary research shows that CN0 might play an important role in the detection of pheromones.

I. Olfactory nerve is sensory in nature and is located in the olfactory foramina of ethmoid. The main function of this nerve is to send the sense of smell to the brain.

II. Optic nerve is a cranial nerve located in the optical canal and this is sensory in nature. The primary function of this nerve is to send out visual information to the brain.

III. Oculomotor is a cranial nerve located in the superior orbital fissure. This nerve is motor in nature .The functions of this nerve include stimulating levator palpebrae superioris, medial rectus, superior rectus, inferior rectus and inferior oblique to jointly perform most of the eye functions.

IV. Trochlear nerve is a type of cranial nerve and located in the superior orbital fissure. This nerve is motor in nature and its primary function is to stimulate the superior oblique muscle whose function is to depress, pull laterally and intort the eyeball.

V. Trigeminal nerve is a cranial nerve located in the superior orbital fissure, foramen rotundum, and foramen ovale. This nerve is both sensory and motor in nature. The primary functions of this nerve include receiving sensations from the face and stimulating the muscles of mastication.

VI. Abducens nerve is a cranial nerve located in the superior orbital fissure. This nerve is motor in nature. The primary function of this nerve is to stimulate the lateral rectus which seizes the eye.

VII.Facial nerves are the cranial nerves which are located and run through the internal acoustic canal to the facial canal and come out from the stylomastoid foramen. This nerve is both sensory and motor in nature. The primary functions of the nerve include providing motor stimulation to the muscles controlling the facial expressions and the stapedius muscle. This nerve also receives the unique sense of taste from the tongue and provides stimulation to the salivary and lacrimal glands.

VIII.Vestiibulocochlear nerve is also known as auditory- vestibular nerve or statoaoustic nerve and is located in the internal acoustic canal. It is sensory in nature .The primary function of this nerve includes sensing sounds, rotation and gravity which is very essential for balance and movement.

IX Glossopharyngeal nerve is a Cranial nerve located in the jugular foramen. The nerve is both sensory and motor in nature and its main functions include receiving taste from the tongue, providing motor stimulation to the stylopharyngeus and providing secretomotor stimulation to the parotid gland.

X Vagus nerve is a cranial nerve located in the jugular foramen and is both sensory and motor in nature. The main function of this nerve is to control the muscle for voice and tone and the soft palate. Other functions include supplying branchiomotor stimulation to most of the laryngeal and pharyngeal muscles. It also provides parasympathetic fibers to most of the thoracic and abdominal viscera and it also receives the special sense of taste from the epiglottis.

XI Accessory nerve also known as cranial accessory or spinal accessory nerve is located in the jugular foramen and is motor in nature. The main function of the nerve is to control the muscles of the neck.

XII Hypoglossal nerve is located in the hypoglossal canal and is motor in nature is extremely important for swallowing and formation of speech. It also provides motor stimulation to the muscles of the tongue and other glossal muscles