Before You Begin
Question #47472
The Question
During a severe systemic allergic reaction (anaphylaxis), IgE-mediated mast cell degranulation releases massive amounts of histamine. This leads to a precipitous drop in blood pressure, overpowering the body's compensatory sympathetic neural control. At the level of the vascular smooth muscle membrane, which of the following best explains how this widespread inflammatory cascade functionally overrides localized neural vasoconstrictor signals?
Options
- A.
Histamine directly blocks the presynaptic release of noradrenaline, preventing the generation of Excitatory Post-Synaptic Potentials (EPSPs) in the vascular smooth muscle.
- B.
Widespread histamine binding activates secondary messengers that induce hyperpolarization or prevent depolarization of the smooth muscle, rendering localized sympathetic depolarizing signals ineffective.
- C.
Histamine binds competitively to the post-synaptic alpha-adrenergic receptors, acting as an antagonist to prevent Na+ influx and subsequent muscle contraction.
- D.
The inflammatory cytokine storm physically degrades the post-synaptic membrane of the vascular smooth muscle, permanently destroying its voltage-gated ion channels.
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
Neurotransmitter Receptor Specificity|Allergy Mechanism|Mast Cell Degranulation
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Integration of Chemical and Neural Coordination.
Students often fail to synthesize how systemic chemical mediators (like histamine) interact with neural control at the effector organ level.
The misconception is assuming histamine acts as a direct neural antagonist (Option C) or blocks neurotransmitter release (Option A), rather than understanding that it acts via its own specific receptors and secondary messengers to alter the post-synaptic membrane potential (hyperpolarization), thereby physiologically overriding the neural depolarizing signals.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Neural Control and Coordination - Class 11 |
| Concept | Neurotransmitter Receptor Specificity |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |