Biology Nervous Coordination SZABMU 2024
PMDC Verified Question 23 of 86
The neurotransmitters bind to the receptors on the postsynaptic membrane, triggering an action potential in the postsynaptic membrane by causing changes in:
A
Permeability of calcium ions
B
Concentration of certain ions
C
Permeability of certain ions
D
Concentration of calcium ions
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: Permeability of certain ions
Concept:

Neurotransmitters act as keys that unlock highly specific gates on the receiving cell.

Solution:

  • Receptors on the postsynaptic membrane are actually ligand-gated ion channels. When a neurotransmitter binds, it physically alters the shape of the channel, changing the membrane's permeability to certain ions (like allowing \(\text{Na}^+\) to rush in). This change in permeability allows ions to flow, altering the electrical potential.


Why other options are incorrect:

  • Concentration: Neurotransmitters don't directly alter the overall concentration of ions; they just open the gates (change permeability) so ions can move down their pre-existing concentration gradients.


  • Calcium ions: Postsynaptic excitation relies primarily on Sodium and Potassium permeability, not Calcium.

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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