Question

The number of cranial nerves in a mammal including man is
A. 10 (5 pairs)
B. 12 (6 pairs)
C. 24 (12 pairs)
D. 36 (18 pairs)

Answer 1

Hint: In mammals, the first two pairs of cranial nerves arise from the cerebrum, while the other ten pairs originate from the brain stem.

Complete answer:
- Cranial nerves are nerves that originate immediately from the brain and are conventionally considered to be twelve pairs. Cranial nerves send information from the brain and areas of the body, mainly to and from the areas of the head and spine, including special senses of taste, vision, scent, and hearing.

- Cranial nerves originate from the central nervous system above the position of the first vertebrae. Each paired cranial nerve is present on both sides. Cranial nerves are called components of the peripheral nervous system, while olfactory, optic, and trigeminal nerves are called more specifically to be members of the central nervous system at the structural level. Cranial nerves are in contrast to spinal nerves that originate from the branches of the spinal cord.

- Cranial nerves provide routes inside and outside the brain. The paths inside the skull are called "intracranial" and the paths beyond the skull are termed as "extracranial." There are also gaps in the skull known as "foramina" via which the nerves can come out of the skull. Both cranial nerves are paired, which means that they appear on both the right and left sides of the body.

- The muscle, tissue, or alternate role of the nerve on the same side of the body as the side from which it originates is an ipsilateral role. If the function is on the opposite side of the root of the nerve, it is known as a contralateral function.
There are 12 pairs of cranial nerves and these pairs of nerves travel into the foramina in the skull, either individually or in groups.

Thus, the correct answer is option C. i.e., 24 (12 pairs).

Note: Cranial nerves are a group of 12 paired nerves that derive directly from the brain. The first two nerves originate from the cerebrum, while the other ten originate from the brain stem.