Question

Which of the following is the smallest cranial nerve?
A. Optic
B. Trochlear
C. Facial
D. Abducence

Answer 1

Hint: Human neural consists of two branches. They are the central nervous system and peripheral nervous system. The central nervous system is made up of the brain and spinal cord. The peripheral nervous system consists of sensory and motor neural pathways. Twelve pairs of cranial nerves and thirty-one pairs of spinal nerves are present in humans.

Complete Answer:
- The functional or cellular units of the nervous system is called the neuron. Bundles of nerve fibres in CNS are called nerve tracts and in PNS, they are referred to as Nerves.
- The olfactory nerve is the first cranial nerve. It helps with the perception of a smell. The optic nerve is the second one and it is responsible for vision. Oculomotor, Trochlear, Abducent are the third, fourth, and sixth cranial nerves respectively. These nerves help in regulating the size and shape of the pupil, ocular movements, Light reflex, etc.
- The fifth cranial nerve is the trigeminal nerve. This nerve is responsible for the sensations over the face, corneal reflexes, conjunctival reflexes, etc. The seventh cranial nerve is the facial nerve. Facial nerve helps for the taste perception over the anterior part of the tongue, controlling facial muscles, etc.
- The vestibulocochlear nerve is the eighth cranial nerve and the glossopharyngeal nerve is the ninth one. Vagus nerve, Accessory nerve, and Hypoglossal nerve are the tenth, eleventh, and twelfth cranial nerves respectively.
- The trochlear nerve is the smallest cranial nerve. It is the fourth cranial nerve. Emerging from the brain, it has the shortest course as it terminates by innervating a muscle present in the eye.

Hence the correct option is B.

Note: Trigeminal nerve is the largest nerve among the cranial nerves. It is the fifth cranial nerve. Vagus nerve is the longest cranial nerve. It is responsible for nasal twang, nasal regurgitation, palatal reflex, pharyngeal reflex, etc.