Neco 2020 Biology Question 6

Practice objective / multiple choice question 6 from the 2020 Neco Biology examination.

Neco 2020 Biology Objective / Multiple Choice Medium Difficulty
Question 6 NECO • 2020 • BIOLOGY • objective
Neco 2020 Biology Question 6 diagram

A single supramaximal electrical stimulus is applied to an isolated frog skeletal muscle fibre. The time from stimulus to the attainment of peak twitch tension is recorded under three conditions: (i) control (no drug) - 30 ms, (ii) after adding nifedipine, a blocker of voltage‑gated L‑type calcium channels - 55 ms, (iii) after adding cyclopiazonic acid, an inhibitor of the sarcoplasmic‑reticulum Ca²⁺‑ATPase (SERCA) - 70 ms. Using knowledge of excitation‑contraction coupling, indicate which physiological step is primarily responsible for the increased time in (ii) and (iii) and briefly explain the mechanism.

Answer Options

A. (ii) inhibition of voltage‑sensitive Na⁺ channels; (iii) blockage of Ca²⁺ release channels (ryanodine receptors) in the sarcoplasmic reticulum
B. (ii) impaired depolarization of the T‑tubule membrane; (iii) increased Ca²⁺ release from the sarcoplasmic reticulum
C. (ii) reduced Ca²⁺ influx through L‑type channels; (iii) accelerated Ca²⁺ re‑uptake into the sarcoplasmic reticulum
Correct Answer D. (ii) delayed Ca²⁺ release from the sarcoplasmic reticulum; (iii) slowed Ca²⁺ re‑uptake into the sarcoplasmic reticulum
Correct Answer
D
Correct Option:
(ii) delayed Ca²⁺ release from the sarcoplasmic reticulum; (iii) slowed Ca²⁺ re‑uptake into the sarcoplasmic reticulum

About This Question

This is Neco 2020 Biology Question 6. It is one of the objective questions from the 2020 Neco Biology examination.

Difficulty level: Medium .

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