Biology Nervous Coordination UHS 2024
PMDC Verified Question 13 of 86
During non-conducting state, the neuron membrane is permeable to efflux of:
A
Ca+
B
K+
C
Na+
D
Cl-
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: K+
Concept:

The resting membrane potential (-70 mV) is primarily established by the membrane's selective permeability to certain ions while at rest.

Solution:

  • During the non-conducting (resting) state, voltage-gated channels are closed, but un-gated "leak" channels remain open. The membrane has significantly more Potassium (\(\text{K}^+\)) leak channels than sodium leak channels, allowing a continuous outward leakage (efflux) of \(\text{K}^+\) down its concentration gradient, keeping the inside of the cell negative.


Why other options are incorrect:

  • \(\text{Na}^+\) / \(\text{Ca}^{2+}\): Their permeability is exceedingly low at rest; allowing them to freely diffuse would instantly destroy the 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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