Chapter 8, Problem 1CRQ

Summary Introduction

To list: The twelve pairs of cranial nerves in the numerical order.

Introduction: The nerves that emerge directly from the brain, in contrast to the spinal nerve, is said to be the cranial nerves. Cranial nerves serve an important role in conveying information between the brain and the bodily parts. There are 12 cranial nerves in humans and it is assigned as Roman numerals from I-XII. The cranial nerves are numbered based on the order in which they usually originate from the brain.

Explanation of Solution

The Roman numeral for the cranial nerve olfactory is I. The olfactory nerve includes only a special sensory constituent (special sense of olfaction) that is responsible for the sense of smell.

The second cranial nerve is the optic nerve (II). The optic nerve is found in the back of the eye. The major responsibility of the cranial nerve is to convey the visual information from the retinal region to the brain exactly in the vision center through electrical impulses.

The third cranial nerve is the oculomotor nerve (III), which is responsible for the movement of the eyeball and eyelid, lens accommodation, and pupillary contraction.

The fourth cranial nerve is the trochlear nerve (CN IV), which is a motor nerve. The trochlear nerve supplies only one muscle known as the superior oblique. The cell bodies that emerge the IV cranial nerve are sited in the ventral portion of the brain (trochlear nucleus).

The fifth cranial nerve is the trigeminal nerve (V) that includes both the sensory as well as motor function. The major responsibility of the trigeminal nerve is to convey sensory information to the sinuses, skin, and the mucous membrane that are present in the face.

The sixth paired cranial nerve is the abducens (VI). The abducens nerve, also known as abducent nerve, originates from the abducens nucleus in the pons of the brain stem. The abducens nerve is a somatic efferent nerve. It controls the lateral rectus muscle of the eye.

Facial nerves (VII) are nerves that are present on the face, scalp, and side of the neck. It is the seventh cranial nerve.

The eighth cranial nerve is the vestibulocochlear nerve (CN VIII). The vestibulocochlear nerve is responsible for carrying the somatic afferent fibers from the inner ear.

The ninth cranial nerve is the glossopharyngeal nerve (IX), which is a mixed nerve. It transmits efferent motor as well as the afferent sensory information.

The tenth cranial nerve that connects the brain to the body is the vagus nerve (X). It is the longest of all the cranial nerves. The vagus nerve controls the inner nerve center and communicates motor as well as the sensory impulse to all the bodily parts.

The accessory nerve (XI) is a motor nerve and its roots originate from the medulla and the cervical column. It is the XI paired cranial nerve. It possesses a somatic motor function. The accessory nerve controls the neck muscle movement and it is coiled in appearance.

The twelfth cranial nerve is the hypoglossal nerve (XII). It innervates all the intrinsic and extrinsic muscles of the tongue. However, the palatoglossus is innervated by a nerve called the vagus nerve.