Gce Model Questions Vol1 2025 Biology Question 47

Practice objective / multiple choice question 47 from the 2025 Gce Model Questions Vol1 Biology examination.

Gce Model Questions Vol1 2025 Biology Objective / Multiple Choice Medium Difficulty
Question 47 GCE_MODEL_QUESTIONS_VOL1 • 2025 • BIOLOGY • objective

A neuron's resting membrane potential is \(-70\ \text{mV}\) and the threshold for firing is \(-55\ \text{mV}\). During a depolarising stimulus the membrane potential rises at a constant rate of \(0.5\ \text{mV ms}^{-1}\) for the first 10 ms. After 10 ms voltage‑gated Na\(^+\) channels begin to inactivate, reducing the depolarisation rate by 40 %. The stimulus continues for a total of 30 ms. Does the neuron reach threshold? If it does, state the time (in ms) at which it fires; if it does not, give the membrane potential at the end of the stimulus.

Answer Options

Correct Answer A. No; the membrane potential reaches \(-59\ \text{mV}\), which is below the threshold.
B. No; the membrane potential reaches \(-58\ \text{mV}\), which is below the threshold.
C. Yes; the neuron fires at \(22\ \text{ms}\).
D. No; the membrane potential reaches \(-60\ \text{mV}\), which is below the threshold.
Correct Answer
A
Correct Option:
No; the membrane potential reaches \(-59\ \text{mV}\), which is below the threshold.

About This Question

This is Gce Model Questions Vol1 2025 Biology Question 47. It is one of the objective questions from the 2025 Gce Model Questions Vol1 Biology examination.

Difficulty level: Medium .

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