Question

Identify the true statement regarding the given nerve action potential curve?

• A. The threshold point is at A
• B. At point E, the nerve is more excitable
• C. Point B to D is a refractory period
• D. Point B to D is a refractory period

Answer 1

The Correct Option is D

In order to determine the true statement about the nerve action potential curve, we must analyze the phases of the action potential.

1. Threshold Point: The threshold is typically the point where the action potential is initiated, leading to a cascade of ion exchanges. In standard curve depictions, this point precedes the action potential spike.
2. Excitability at Point E: After an action potential, there is a period of relative inexcitability followed by recovery phases where the nerve returns to normal potential, making the statement about point E incorrect.
3. Refractory Period (Point B to D): This period occurs immediately after an action potential is fired and can be divided into:
   • Absolute Refractory Period: During which no new action potential can be initiated, because the sodium channels are inactivated.
   • Relative Refractory Period: At the tail end, a stronger-than-normal stimulus is required to initiate another action potential due to continued potassium channel activity.
   The region described from B to D represents this zone of reduced excitability, supporting the given correct answer.

Therefore, the statement "Point B to D is a refractory period" is the correct identification in relation to the nerve action potential.