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Question #47463
The Question
Evolutionarily, immediate survival reflexes (e.g., withdrawal response) are governed by neural pathways utilizing fast ligand-gated ion channels rather than endocrine-like G-protein coupled receptors (GPCRs). In an experimental model, the ionotropic receptors at a reflex arc's neuromuscular junction are replaced by GPCRs that utilize the cAMP secondary messenger cascade. Additionally, a mutation is introduced in the G-alpha subunit of these receptors, abolishing its intrinsic GTPase activity. Upon receiving a threshold stimulus, which of the following physiological outcomes is most likely?
Options
- A.
The reflex response will occur with normal millisecond latency, but the effector muscle will fail to relax due to continuous adenylate cyclase activation.
- B.
The reflex response will be significantly delayed due to the time required for signal transduction, followed by a prolonged, sustained effector response.
- C.
The reflex arc will fail to initiate any response because the inability to hydrolyze GTP prevents the dissociation of the G-alpha subunit from the beta-gamma complex.
- D.
The reflex response will be delayed, but the effector will relax immediately after contraction because cAMP is rapidly degraded by phosphodiesterase regardless of G-protein state.
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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
Reflex Arc Latency|Secondary Messenger Cascade|Hormone Receptors Location
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Distinguishing between the activation phase (GTP binding) and the termination phase (GTP hydrolysis) of G-proteins, while simultaneously applying the physiological concept of synaptic delay differences between ionotropic and metabotropic receptors.
A common misconception is that GTPase activity is required to initiate the signal, whereas it is actually required to terminate it.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Neural Control and Coordination - Class 11 |
| Concept | Reflex Arc Latency |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |