Question

There are how many pairs of cranial nerves in humans?
A. 8
B. 12
C. 25
D. 31

Answer 1

Hint: Nerves emerging directly from the brain are called cranial nerves. They relay information between the brain and the body, mostly to and from the neck and head region.

Complete step by step answer:
Cranial nerves emerge from the brain directly. They are responsible for most of the motor and sensory functions of the head and the neck, like balance, hearing, swallowing, eye movement, smell and sight.
Some cranial nerves also have branches that control tasks like gastro intestinal peristalsis, heart rate, muscle movement in the mouth, speech, and sweating.
There are 12 cranial nerves in humans namely:
- Olfactory nerve (I), responsible for the sense of smell and has the capability to regenerate.
- Optic nerve (II) that carries information from the retina to the brain.
- Oculomotor nerve (III), controls the movement of the eye, opening of eyelids and constriction of pupils.
- Trochlear nerve (IV), a motor nerve, responsible for the rotational eye movement as it innervates the superior oblique muscle of the eye.
- Trigeminal nerve (V), responsible for the motor sensation of the face muscles.
- Abducens nerve (VI), supplies nerves to the lateral rectus muscle of the eye which regulates the lateral movement of the eye.
- Facial nerve (VII), controls the facial expression muscles and conveys taste sensation to two third of the anterior portion of tongue and oral cavity.
- Vestibulocochlear nerve (VIII), transmits sound and balance (equilibrium) information signals from the inner ear to the brain.
- Glossopharyngeal nerve (XI), receives sensory information from the pharynx, tonsils, middle ear and tongue.
- Vagus nerve (X), has branching and is responsible for multiple functions like heart rate, keeping the larynx open for breathing, gastro intestinal peristalsis, sweating, speech and mouth muscle movement.
- Spinal accessory nerve (XI), controls muscles of the neck and shoulders.
- Hypoglossal nerve (XII), controls peristalsis and swallowing, speech and tongue movements.
Hence the correct answer is option B.

Note: The spinal nerves are 34 in number with 8 being cervical, 13 thoracic, 6 lumbar, 4 sacral, and 3 caudal. They are attached to the cranial nerves for impulse transmission.