Question

For visual sense , the nerve impulse is generated by
A) Depolarisation
B) Repolarisation
C) Hyperpolarization
D) Depolarisation and repolarisation

Answer 1

Hint: Initially any nerve is in the resting potential stage but when an impulse is generated it is depolarised and an action potential is generated which is responsible for the transmission of the impulse.

Complete step by step answer:
Polarisation: In the resting stage When nerves are not stimulated, the charge is distributed such that outside of the membrane positive charge is in abundance while inside the membrane there is an abundance of negative charge. This state is called the polarisation state.
Depolarisation: When the stimulus is received by the neuron, its polarity changes which results in lowering the negative charge inside the membrane and overall positive charge inside the membrane and negative charge out the membrane. This change in polarity is called depolarisation, when a nerve is at rest then the potential difference across it is called resting potential and this potential difference is due to polarisation, but when the stimulus is given then action potential is generated due to depolarisation. After the end of the stimulus, it is necessary for the neuron to get back in its original condition in order to get the further stimulus. So the neuron again comes back in its original condition through repolarisation and again resting potential is restored.
Optic nerves from the eye carry the visual sense to the occipital lobe of the forebrain.
So, the correct answer is option (A),i.e., as nerve impulse is generated by depolarisation.

Note: For the generation of resting potential, $N{a^ + }/{K^ + }$pumps are involved. These are the proteins which are present across the cell membrane of an animal cell. It pumps 3 $N{a^ + }$ outside the cell and 2 ${K^ + }$ inside the cell, creating an overall positive charge outside and negative charge inside of the cell.