At the end of repolarization, the nerve is hyperpolarized. How does the membrane potential return to RMP?
**Core Concept**
The repolarization phase in neurons is a complex process that involves the closure of voltage-gated sodium channels and the opening of potassium channels, leading to the efflux of potassium ions and the influx of chloride ions. This process ultimately returns the membrane potential to its resting state (RMP).
**Why the Correct Answer is Right**
The correct answer involves the concept of potassium channels and their role in repolarizing the membrane. During repolarization, the voltage-gated sodium channels close, and the membrane potential becomes more negative due to the efflux of potassium ions through open potassium channels (K+ channels). This is facilitated by the inwardly rectifying potassium channels (Kir channels) and the voltage-gated potassium channels (Kv channels). The influx of chloride ions (Cl-) also contributes to repolarization by increasing the negativity of the membrane potential.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not specify the role of potassium channels in repolarization. While the influx of chloride ions does contribute to repolarization, it is not the primary mechanism.
* **Option B:** This option is incorrect because it suggests that repolarization occurs through the influx of sodium ions, which is not the case. Sodium channels close during repolarization, and the membrane potential becomes more negative due to potassium efflux.
**Clinical Pearl / High-Yield Fact**
The resting membrane potential (RMP) is typically around -70 mV, with the inside of the neuron being negative relative to the outside. This is due to the high concentration of potassium ions inside the neuron and the low concentration of potassium ions outside the neuron.
**Correct Answer:** C.