Medicograspers | Neuroanatomy notes | Cranial Nerves Overview |

Cranial nerves overview:

In this article, we will look at the overview of cranial nerves.

• Cranial nerves arise from the brain.
• Except for the optic nerve, the other 11 cranial nerves divide and form the part of the PNS. The optic nerve doesn’t branch like the other cranial nerves. It's just the extension of the central nervous system.
• S- sensory and M – motor and B- both.
• Mneumonic for sensory and motor nerves are listed below.

Some Say Marry Money But My Brother Says Big Brain Matter More

 

1.     olfactory nerve: S

They pass through the cribriform plate of the ethmoid bone and they synapse with the olfactory bulb and connects to the olfactory tract and relays the olfactory sensation to the brain.

2.     Optic nerve: S

This nerve is responsible for vision. These nerves synapse at the junction named optic chiasm.

3.     Oculomotor nerve: M

This nerve originates from the interpeduncular fossa which is present in between the cerebral peduncles of the midbrain. This nerve is responsible for the motor movement of the extraocular muscles and the pupillary sphincter muscles. 

4.     Trochlear nerve: M

This nerve is responsible for the motor control of the Superior oblique muscle of the eye. This nerve originates on the dorsal midbrain below the corpora quadrigemina and twines around the cerebral peduncles and supplies the SO muscle. Pneumonic: (LR6SO4)

5.     Trigeminal nerve: B

This nerve is responsible for the sensation of the face and also responsible for the movement of muscles of mastication. This fatty nerve originates from the middle cerebellar peduncle which connects the pons and the cerebellum. This nerve has the ganglion (a group of cell bodies outside the CNS) named trigeminal ganglion and from there, this nerve divides into V1(ophthalmic division), V2(maxillary division), V3(mandibular division).

6.     Abducens nerve: M

This nerve originates from the border between the pons and the medulla oblongata and this nerve is responsible for the motor movement of the lateral rectus (LR6SO4). Therefore, the nerves supplying the extraocular muscles are,

Trochlear, abducens, and the oculomotor nerve.

7.     Facial nerve: B

This nerve originates from the cerebellopontine angle above the olivary or olive body of the medulla oblongata. This nerve is responsible for: motor function – muscles of facial expression; sensory function – perceives taste from the anterior 2/3 of the tongue; secretory motor function – salivary gland, lacrimal gland.

8.     Vestibulocochlear nerve: S

This nerve also arises from the cerebellopontine angle.

·       Vestibular portion – balance

·       Cochlear portion – hearing

9.     Glossopharyngeal nerve: B

This nerve arises from the dorsal side of the olivary part of the medulla oblongata.

·       Sensory – perceives taste from the posterior 1/3 of the tongue and sensation from various areas of the throat.

·       Motor – muscles of the throat, secretomotor function to the parotid gland.

10. Vagus nerve: B 

This nerve originates just below the glossopharyngeal nerve, behind the olive and on the postero-lateral side of the medulla oblongata. This nerve innervates the pharyngeal, laryngeal muscles abdominal, and thoracic viscera.

11. Accessory nerve: M

Origin: it has cranial and spinal roots. Innervates the sternocleidomastoid and the trapezius muscle.

12. Hypoglossal nerve: M

This nerve originates between the medullary pyramid and the olivary part of the medulla. This nerve innervates the muscles of the tongue.