''We withdraw our leg when stepped on thorn unknowingly."
i] Trace the sequences of events which occur in this action.
ii] Which part of human nervous system controls this action?

Explanation

a] i] Receptors receive the stimulus of pain
ii] Messages reach spinal cord through sensory neuron.
iii] Responses reach motor neuron through associationneuron.
iv] Responses reach effector through motor neuron.
v] Muscles withdraw the leg.
b] Spinal cord/reflex arc.