Question

How many pairs of cranial nerves are purely sensory?
a. 2
b. 3
c. 4
d. 5

Answer 1

Cranial nerves are the specialized nerves that connect the brain to a different part of the body such as the head, neck, limbs, etc. All the nerves are interconnected and reach the brain nerve switch from where synapses are electrocuted and produced. There are twelve pairs of cranial nerves. Each never has a specific name and a unique function to perform.

Complete answer:
- Within 12 pairs of nerves, they are divided into 3 categories.
- Cranial nerves 1,2,8 are the pure sensory nerves.
- Cranial nerves 3,4,6,11,12 are pure motor nerves.
- Another left like 5,7,9,10 are mixed nerves, they are motor and sensory mixed nerves.
- These have some specific names and particular functions, no nerve can perform a different function.
- Such as for the smell olfactory nerve is assigned which is nerve 1.
- For vision, the optic nerve which is nerve 2.
- The facial nerve is nerve 7 which is a motor nerve that provides innervation to the muscle of facial expression, sublingual gland or submaxillary gland.
- All the nerves like terminal nerves, optic, and olfactory nerves emerge from the cerebrum and the remaining ten pairs arise from the brainstem which is the lower part of the brain.
- Spinal cord segments produce or emerge spinal nerves which are in contrast to cranial nerves.

Hence, the correct answer is option (B).

Note: Cranial nerves supply various functions such as smell, vision, movements. Anatomy of the cranial nerves gives rise to several ganglia, which is a collection of cell bodies of neurons in the nerves which are usually outside the brain. Ganglia can be parasympathetic and sensory ganglia. Their development is the cranial neural crest and ectodermal placodes.