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Question #47421

Difficulty: 8/10 | 🟢 Free

The Question

A neurobiologist observes that treating a specific group of neurons with a lipid-soluble steroid hormone for 12 hours significantly increases the magnitude of the excitatory stimulus required to generate an action potential. Which of the following mechanisms best explains this physiological shift?

Options

A.
The hormone binds to an intracellular receptor, and the complex acts as a transcription factor to upregulate $K^+$ leak channels, causing hyperpolarization.
B.
The hormone binds to a membrane-bound receptor, activating a second messenger cascade that rapidly phosphorylates and inactivates voltage-gated $Na^+$ channels.
C.
The hormone-receptor complex interacts with the genome to downregulate the synthesis of $Na^+/K^+$ ATPase pumps, making the resting membrane potential more positive.
D.
The hormone directly binds to voltage-gated $K^+$ channels on the axolemma, increasing their open probability and delaying depolarization.

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

Steroid_Receptors|Voltage_Gated_K_Channels|Threshold_Logic

Why This Question Is Tricky

Common Mistakes

Conceptual Pivot: Bridging the 'genomic action' of steroid hormones (NCERT Class 11 Ch 22) with the ionic determinants of Resting Membrane Potential (NCERT Class 11 Ch 21).

Common Misconception: Students often memorize hormone mechanisms and neural conduction in isolation.

They fail to realize that 'slow' changes in neuronal excitability are due to altered transcription of ion channel subunits, whereas 'fast' changes are due to direct channel gating.

Furthermore, students frequently confuse the directional shift of RMP; hyperpolarization makes a neuron harder to fire (requires a larger stimulus), while depolarization makes it easier.

Quick Facts About This Question

Question Information

Subject	Biology
Chapter	Neural Control and Coordination - Class 11
Concept	Action Potential Threshold Logic
Difficulty	8
Cognitive Load	5
Target Solve Time	120 sec
Access	Free