Question

On touching a hot plate u suddenly withdraw your hand which category of neurons become active first and which next

Answer 1

The first neurons to be involved here are the sensory neurons followed by the interneurons. 

The action of withdrawing the hand is termed as a reflex action. Reflex actions are not under control of the conscious mind. Reflexes are involuntary responses to stimulus.

In this case here the reflex is the withdrawal of the hand while the stimulus is the hot plate. 

Reflex actions are made possible by neural pathways called reflex arcs that need no intervention of the brain.

Reflex arcs contain:

i) Receptors - these are the organs ones that sense the stimuli.

ii) Sensory neurons - these are neurons in the reflex arc that carry impulses of the stimuli from the receptor towards the Central Nervous System (CNS). 

iii) Interneurons - these are the neurons in the CNS, that carry impulses within the CNS.

iv) Motor neurons - these are the neurons that carry the impulses away from the CNS towards.

v) Effector - this is the organ that receives the impulse from the motor neurons and causes a response. Examples include muscles and glands. In this case here the effector is the muscles that cause the hand to withdraw from the hot plate. 

Answer 2

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