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Question #46370
The Question
Intense stimulation of the vagus nerve supplying the heart leads to the release of a specific neurotransmitter that acts on the atrioventricular (AV) node. Which of the following correctly identifies the resulting primary ionic shift in the nodal tissue and its direct consequence on the Electrocardiogram (ECG)?
Options
- A.
Increased K+ efflux leading to hyperpolarization; Prolongation of the P-R interval
- B.
Increased Ca2+ influx leading to rapid threshold achievement; Shortening of the P-R interval
- C.
Decreased K+ efflux leading to delayed repolarization; Prolongation of the Q-T interval
- D.
Increased Na+ influx leading to accelerated depolarization; Narrowing of the QRS complex
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Comparative_Analysis
Sharpen your ability to evaluate multiple scenarios and distinguish between competing potential answers.
Concepts Behind This Question
Regulation of Cardiac Activity|Synaptic Delay Determinant|ECG Wave Interpretation
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize that the vagus nerve 'slows the heart' but fail to link the cellular ionic mechanism (hyperpolarization via K+ efflux) to the specific dromotropic ECG manifestation (P-R interval prolongation).
The trap lies in confusing the ionic basis of standard neural action potentials with cardiac nodal tissue, and misattributing AV nodal delay to the QRS complex or Q-T interval.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Body Fluids and Circulation - Class 11 |
| Concept | ECG Wave Interpretation |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |