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.  Cranial nerves and spinal nerves. 

(a) Differences between Afferent neuron and Efferent neuron.

Afferent neuron	Efferent neuron
It conducts impulses from peripheral receptors and tissue to central nervous system	It conducts impulses from central nervous system to effectors
It provides stimulus and evokes sense.	It results in the response by the effectors (muscles and glands)
They are sensory in nature.	They are motor in nature.

(b) Conduction of nerve impulse in myelinated and non- myelinated nerve fibre.

Conduction of nerve impulse in myelinated nerve fibre.	Conduction of nerve impulse in on- myelinated nerve fibre
Complete electrical insulation is provided to axon.	No perfect insulation.
Flow of ions associated with passage of nerve impulse is restricted to nodes of Ranvier and only small amount of ions pass.	Flow of ions occurs all along the fibre and large amount of ions pass along its length.
Impulse is conducted by saltatory conduction.	Impulse is conducted by steadily progressing ionic charge along the length.
Velocity of conduction increases.	Velocity of conduction is slow.
Less amount of energy is required.	More amount of energy is required.

(c) Differences between vitreous humor and aqueous humor.

Vitreous humor	Aqueous humor
It is thick jelly- like fluid present between retina and lens.	It is watery fluid present between lens and cornea.
It is of permanent nature and not replaced.	It is continuously secreted and drained out of eyes.
It does not have nutritive value.	It provides nourishment to lens, cornea and other parts of anterior chamber.

(d) Difference between yellow spot and blind spot

Yellow spot	Blind spot
1. It has only cone cells and sharp image is formed at this spot.	1. It has neither cone nor rod cells and no image is formed.

Difference between cranial nerves and spinal nerves.

Cranial Nerves	Spinal Nerves
They originate from the brain.	They originate from the spinal cord.
They may be sensory, motor or mixed.	They are all mixed in nature.