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Question #46867
The Question
An experimental toxin selectively degrades the gap junctions located within the intercalated discs of the human heart, while leaving the autonomic neural innervation and SA node receptors completely intact. If the sympathetic nerve to the heart is strongly stimulated in the presence of this toxin, which of the following physiological outcomes is most likely?
Options
- A.
The SA node will exhibit a positive chronotropic response, but the ventricular myocardium will fail to contract as a synchronized unit.
- B.
The generation of action potentials at the SA node will cease, as gap junctions are essential for the auto-rhythmic influx of sodium ions.
- C.
The sympathetic neurotransmitters will fail to initiate a response because intercalated discs act as the primary receptors for autonomic neural inputs.
- D.
The ventricles will undergo a synchronized but weaker contraction, as gap junctions only regulate the inotropic (force) response, not the chronotropic (rate) response.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Regulatory_Failure
Understand how NOT, EXCEPT, and logical constraints are used to manipulate exam results.
Concepts Behind This Question
Intercalated Disc Function|Neurotransmitter Receptor Specificity|Regulation of Cardiac Activity
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often confuse the 'generation' of the cardiac impulse (myogenic auto-rhythmicity via SA node) with the 'propagation' of the impulse (electrical continuity via gap junctions in intercalated discs).
The trap lies in assuming that because the sympathetic nervous system is stimulated, the entire heart will automatically beat faster, ignoring the structural requirement (intercalated discs) needed to relay that neural command to the working ventricular myocardium.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Structural Organisation in Animals - Class 11 |
| Concept | Intercalated Disc Function |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |