15 Facts About Cranial nerves

Cranial nerves are the nerves that emerge directly from the brain, of which there are conventionally considered twelve pairs.

Cranial nerves emerge from the central nervous system above the level of the first vertebrae of the vertebral column.

The numbering of the cranial nerves is based on the order in which they emerge from the brain and brainstem, from front to back.

Cranial nerves are considered components of the peripheral nervous system, although on a structural level the olfactory, optic, and trigeminal nerves are more accurately considered part of the central nervous system .

Cranial nerves are in contrast to spinal nerves, which emerge from segments of the spinal cord.

The Cranial nerves are: the olfactory nerve, the optic nerve, oculomotor nerve, trochlear nerve, trigeminal nerve, abducens nerve, facial nerve, vestibulocochlear nerve, glossopharyngeal nerve, vagus nerve, accessory nerve, and the hypoglossal nerve .

Cranial nerves are generally named according to their structure or function.

Cranial nerves are numbered based on their position from front to back of their position on the brain, as, when viewing the forebrain and brainstem from below, they are often visible in their numeric order.

All cranial nerves are paired, which means they occur on both the right and left sides of the body.

The olfactory Cranial nerves emerge from the olfactory bulbs on either side of the crista galli, a bony projection below the frontal lobe, and the optic Cranial nerves emerge from the lateral colliculus, swellings on either side of the temporal lobes of the brain.

Cranial nerves give rise to a number of ganglia, collections of the cell bodies of neurons in the nerves that are outside of the brain.

Ganglion of the sensory Cranial nerves, which are similar in structure to the dorsal root ganglion of the spinal cord, include:.

Cranial nerves are formed from the contribution of two specialized embryonic cell populations, cranial neural crest and ectodermal placodes.

Cranial nerves provide motor and sensory supply mainly to the structures within the head and neck.

However, because many of the Cranial nerves emerge from the brain stem as rootlets, there is continual debate as to how many Cranial nerves there actually are, and how they should be grouped.