Biology Circulation / Transport SZABMU 2024
PMDC Verified Question 4 of 54
The total delay in the conductance of action potential from SA node to AV node is:
A
0.10 second
B
0.15 second
C
0.08 second
D
0.20 second
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: 0.15 second
Concept:

Electrical impulses must be delayed between the atria and ventricles to allow physical blood filling to occur.

Formula:

None

Solution:

  • The electrical signal travels rapidly from the SA node across the atria to the AV node.


  • The AV node consists of thin fibers with fewer gap junctions, causing a deliberate bottleneck in the electrical signal.


  • This creates a total built-in delay of approximately 0.15 seconds (or 0.1 to 0.15s depending on text). This crucial fraction of a second ensures the atria fully contract and empty their blood into the ventricles before the ventricles begin to contract.


Why other options are incorrect:

  • Values like 0.08s are too short (ventricles would contract while empty), and 0.20s is dangerously close to a first-degree heart block.

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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