Question

Match column-I (various phases of an action potential) with column II (ionic activity associated) and choose the correct option.

	Column-I		Column-II
A.	Resting stage of a neuron	I.	Opening and then the closing of the sodium channels
B.	Depolarisation phase in the generation of the action potential.	II.	All voltage-gated sodium and potassium channels are closed.
C.	Repolarisation phase in the generation of the action potential.	III.	The sodium channels remain open.
D.	Absolute refractory phase.	IV.	Opening of potassium gates and the rushing of potassium

A. A-II; B-I; C-IV; D-III
B. A-I; B-II; C-III; D-IV
C. A-III; B-IV; C-I; D-II
D. A-IV; B-II; C-III; D-I

Answer 1

Hint: The resting stage takes place once the nerve cell is in a steady state. Depolarisation is caused by a rapid rise in membrane potential opening of sodium channels in the cellular membrane, which leads to a big influx of sodium ions. Repolarisation takes place once the outward current exceeds the inward current. The absolute refractory period is a period once the neuron cannot send any more action potentials.

Complete step-by-step answer:
The resting phase takes place once the nerve cell is in a steady state. It maintains resting membrane potential. In this state, the cell can respond to enough stimulus current and produce an action potential. The resting potential of a human neuron nerve cell exists between the Nernst potential for sodium (+58mV) and the Nernst potential for potassium (-80mV). Potassium's potential has a significant impact on resting potential due to its dominance in membrane permeability over sodium. 
The threshold potential opens voltage-gated sodium channels and causes a massive influx of sodium ions. This phase is known as depolarisation. During depolarisation, the inside of the cell becomes increasingly electropositive, if the potential gets nearer to the electrochemical equilibrium for sodium of +61 mV.
Repolarisation is a stage of an action potential where the cell experiences a reduction in voltage because of the efflux of potassium (K+) ions along its electrochemical gradient. This phase takes place after the cell reaches its highest voltage from depolarisation. Depolarisation and hyperpolarisation takes place once ion channels in the membrane close or open, altering the ability of particular kinds of ions to get in or go out of the cell.
The absolute refractory period is a period once the neuron is not able to send additional action potentials. It is triggered by the voltage-gated sodium channels shutting and not opening for a short period of time.

	Column-I		Column-II
A.	Resting stage of a neuron	II.	All voltage-gated sodium and potassium channels are closed.
B.	Depolarisation phase in the generation of the action potential.	I.	Opening and then the closing of the sodium channels
C.	Repolarisation phase in the generation of the action potential.	IV.	Opening of potassium gates and the rushing of potassium.
D.	Absolute refractory phase.	III.	The sodium channels remain open.

Therefore, the correct answer is A Option .
Note: An action potential is a quick increase and subsequent fall in voltage or membrane potential over a cellular membrane with a typical pattern. Adequate current is needed to begin a voltage response in a cell membrane; if the current is not enough to depolarise the membrane to the threshold level, an action potential will not fire. Examples of cells that signal through action potentials are muscle cells and neurons.