Question

Distinguish between:

(a) Afferent neurons and efferent neurons

(b) Impulse conduction in a myelinated nerve fibre and unmyelinated nerve fibre

(c) Aqueous humor and vitreous humor

(d) Blind spot and yellow spot

(e) Cranial nerves and spinal nerves

Answer 1

(a) Afferent neuron conducts nerve impulses toward the brain or the spinal cord and are also called as sensory neurons. While efferent neuron conducts nerve impulses from the brain or spinal cord to the effector organs such as muscles or glands and are also called as motor neurons.

(b) In a myelinated nerve fibre, the action potential is conducted from one node to another and the conduction of impulses is faster. whereas in an unmyelinated nerve fibre, the action potential is not conducted from node to node. It is carried along the whole length of the nerve fibre and the conduction of impulses is slower.

(c) Aqueous humor is a clear liquid found between the cornea and the lens of eye, whereas vitreous humor is a clear gelatinous mass found in the rear part of the eyeball between the lens and retina. Aqueous humor is continuously generated and continuously drains from the front of the eye throughout the lifetime, whereas vitreous humor is produced only during the embryonic stage and stays for the entire lifetime. Vitreous humor does not replenish while aqueous humor does. The volume of vitreous humor is higher than that of aqueous humor in a single eye.

(d) Blind spot is a spot on the retina present at the point of origin of the optic nerve and are insensitive to light as both rods and cones are absent.

Whereas yellow spot is a small area on the retina present at the posterior pole of the eye, lateral to the blind spot and is sensitive to bright light as cones are present.

(e)There are 12 pairs of cranial nerves arises from the brain. While spinal nerves arise from the spinal cord and tThere are 31 pairs of spinal nerves.