Given below are two statements: one is labelled Assertion(A) and other is labelled Reason(R).

Assertion (A): Nerve impulse transmission along an axon is unidirectional.

Reason(R): It converts the chemical energy in ATP to the mechanical energy of motion and generates force.

In the light of above statements, choose the correct answer from the options given below.

Nerve impulse transmission along an axon is unidirectional. This is because  the sodium channels have a refractory period following activation, during which they cannot open again. This ensures that the action potential is propagated in a specific direction along the axon.

Nerve impulse converts the chemical energy in ATP to the mechanical energy of motion and generates force.