Question

Question 12 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

(f) cranial nerves and spinal nerves.

Class - XI - Biology Chapter Neural Control and Coordination Page No. 329

Answer 1

a) Afferent neurons and Efferent neurons

Afferent neurons

Efferent neurons

They conduct impulses towards the central neural system.They conduct impulses away from the central neural systemIt provides stimulus and evoke senses.It results in the response by the effectors.They are sensory in nature.They are motor in nature.These take information from the receptors.These take information to effectors.
b) Impulse conduction in a myelinated nerve fibre and an unmyelinated nerve fibre

Impulse conduction in a myelinated nerve fibre

Impulse conduction in a unmyelinated nerve fibre

The depolarisation occurs only in the nodes of Ranvier where the myelin sheath is absent.The depolarisation occurs all along the length of the nerve fibre.Action potential jumps from one node of Ranvier to another.Action potential travels along the entire length of the fibre.Conduction is faster.Conduction is slower.Less amount of energy is required.More amount of energy is required.
c) Aqueous humour and Vitreous humour

Aqueous humour

Vitreous humour

It is a watery and transparent fluid.It is thick gelly-like transparent fluid It is present between lens and cornea.It is present between lens and retina.It is continuously secreted by ciliary processes and drained out of the eyes.It is not replaced.It provides nourishment to lens, cornea and other parts of anterior chamber.It does not have nutritive value.
d) Blind spot and Yellow spot

Blind spot

Yellow spot

Blind spot is a spot on the retina present at the point of origin of the optic nerve.Yellow spot is a small area on the retina present at the posterior pole of the eye, lateral to the blind spot.It does not have a shallow depression.It has a shallow depression called fovea centralis.Photoreceptor cells are absent from this region.Only cones are present in this region.It is insensitive to light.It is sensitive to bright light.Photoreceptor cells are absent from this region.Only cones are present in this region.No image is formed at the blind spot.An image is formed at the yellow spot.


e) Cranial nerves and Spinal nerves

Cranial nerves

Spinal nerves

They originate from the brain.They originate from the spinal cord.There are 12 pairs of cranial nerves.There are 31 pairs of spinal nerves.These are sensory, motor or mixed in nature.They are mixed in nature.They extend between the brain and body parts.They extend between the spinal cord and body parts.