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Question #45794
The Question
A neurotoxin selectively blocks the voltage-gated Ca2+ channels at the presynaptic terminal of an excitatory chemical synapse in a spinal reflex arc. If a threshold stimulus is applied to the corresponding sensory receptor, which of the following represents the exact physiological consequence?
Options
- A.
The action potential will fail to depolarize the synaptic knob, as Ca2+ influx is strictly required for the terminal phase of axonal conduction.
- B.
Synaptic vesicles will fail to undergo exocytosis, preventing the generation of excitatory postsynaptic potentials (EPSPs) and subsequent temporal summation.
- C.
Neurotransmitters will be released into the synaptic cleft via passive diffusion but will fail to bind to the postsynaptic ligand-gated receptors.
- D.
The postsynaptic neuron will undergo continuous hyperpolarization due to the compensatory opening of voltage-gated Cl- channels.
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
Synaptic_Knob|Voltage_Gated_Ca_Channels|Synaptotagmin
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Differentiating the ionic basis of action potential propagation (voltage-gated Na+/K+ channels) from synaptic transmission (voltage-gated Ca2+ channels).
The trap tests the student's ability to recognize that while the electrical impulse successfully reaches the terminal, the chemical transduction fails entirely, leaving the postsynaptic membrane at a resting state rather than hyperpolarized or passively activated.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Locomotion and Movement - Class 11 |
| Concept | Calcium Dynamics |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |