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Question #47441
The Question
According to the NCERT mechanism of vision, light induces the dissociation of retinal from opsin, resulting in changes in membrane permeability. During prolonged exposure to high-intensity light (photobleaching), the photoreceptor remains in a sustained hyperpolarized state, temporarily halting new signal transmission. Which of the following biochemical scenarios best explains why the photoreceptor fails to immediately reset to its resting 'dark' state?
Options
- A.
Sustained activation of Phosphodiesterase (PDE) keeps cGMP levels critically low, preventing the reopening of cGMP-gated cation channels.
- B.
Accumulation of intracellular Ca²⁺ inhibits Guanylate cyclase, preventing the regeneration of cGMP required for depolarization.
- C.
Continuous release of glutamate from the synaptic terminal exhausts the neurotransmitter vesicles, halting signal transmission.
- D.
The Na⁺/K⁺ pump is directly inactivated by the altered opsin structure, trapping sodium ions inside the outer segment.
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
cGMP|Guanylate_cyclase|Negative_Feedback
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often misinterpret photoreceptor physiology by applying standard neuronal logic (assuming stimulus = depolarization and neurotransmitter release).
The trap in Option B tests the nuanced feedback loop: students may memorize 'Calcium inhibits Guanylate cyclase' but fail to realize that in the light state, Calcium levels actually fall, which is the trigger meant to initiate recovery.
Option A correctly identifies the metabolic exhaustion of cGMP as the root cause of sustained hyperpolarization.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Neural Control and Coordination - Class 11 |
| Concept | Retina Phototransduction Cascade |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |