Assertion (A) : A positive charge applied to the inside of the membrane of the neuron produced depolarization.
Reason (R) : Inside of the membrane was positively charged.
In the context of the above two statements, which one of the following is correct ?
Codes :
Evaluating Neuron Membrane Potential Statements
This question asks to evaluate an Assertion (A) and a Reason (R) regarding changes in a neuron's membrane potential.
Assertion (A) Analysis: Positive Charge Inside Causes Depolarization
Assertion (A) states that applying a positive charge inside the neuron membrane causes depolarization. Depolarization is defined as a change in the membrane potential that makes the inside of the cell *less negative* (or more positive) relative to the outside. Applying a positive charge directly to the inside of the membrane achieves this by increasing the positive charge concentration, thus making the membrane potential less negative. Therefore, Assertion (A) is correct.
Reason (R) Analysis: Inside Was Positively Charged
Reason (R) states that the inside of the membrane was positively charged. In a neuron at rest, the inside of the membrane is actually *negatively* charged relative to the outside (resting potential, typically around -70mV). While the inside *becomes* transiently positive during the peak of an action potential (due to Na+ influx), this is a result of depolarization, not the resting state. As a reason explaining why *applying* a positive charge causes depolarization, this statement is incorrect. It doesn't accurately describe the initial state, nor does it logically explain the effect of an applied charge. Therefore, Reason (R) is wrong.
Conclusion
Since Assertion (A) is correct and Reason (R) is wrong, the correct option is the one that states (A) is correct, but (R) is wrong.
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