Question

Fifth cranial nerve of frog is called as
A. Optic nerve
B. Vagus nerve
C. Trigeminal nerve
D. Ophthalmic nerve

Answer 1

Hint: Frogs are the amphibians that can live in water as well as on land. They have 20 cranial nerves in total. However, these cranial nerves exist in a pair and thus, frogs normally have ten pairs of cranial nerves.

Complete answer:
The 10 pairs of cranial nerves in frogs are olfactory (first pair), optic (second pair), oculomotor (third pair), trochlear (fourth pair), trigeminal (fifth pair), abducens (sixth pair), facial (seventh pair), auditory (eight pair), glossopharyngeal (ninth pair), and vagus (tenth pair) nerves. Therefore, in frogs, the fifth cranial nerve arises from the lateral side of medulla oblongata and is commonly known as trigeminal nerve.
The main function of the trigeminal nerve is to supply sensations to mucous membranes, face and other structures associated with the head of the animal. This fifth cranial nerve is considered as the most important cranial nerve being the largest one, and having sensory as well as motor functions to perform. Trigeminal nerve is also divided further into three divisions or branches.
Optic nerve is the second cranial nerve in frogs, whereas the vagus nerve is located at tenth position. However, opthalmic nerve is one of the three branches of the trigeminal cranial nerve. Other two divisions of this fifth cranial nerve are mandibular and maxillary divisions/nerves.

Hence, the correct answer is (C).

Note:
Cranial nerves are referred to the nerves arising from the brain. These are significantly important for various functions including smell, movement of eyes, sight, chewing, and other sensory or motor functions. Hence, cranial nerves are mainly involved in neck and head functions during their location in those respective areas.