Biology Nervous Coordination MDCAT 2015
PMDC Verified Question 84 of 86
In the following diagram of action potential in a neuron, '2' depicts:

mV +30 -70 1 2 3 4
A
Depolarization
B
Repolarization
C
Polarization
D
Hyperpolarization
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: Depolarization
Concept:

An action potential graph tracks membrane voltage over time, featuring distinct phases dictated by specific ion channels opening and closing.

Solution:

  • Phase 1: Resting state.


  • Phase 2: Depolarization. Voltage-gated \(\text{Na}^+\) channels open, allowing an influx of sodium ions, causing the membrane potential to rapidly become positive.


  • Phase 3 & 4: Repolarization (falling phase).


  • Phase 5: Hyperpolarization (undershoot).


Why other options are incorrect:

  • Repolarization: Occurs during the downward slope of the graph.


  • Hyperpolarization: The dip below the baseline resting potential.

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

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