Relative refractory period occurs during

Options

A. depolarisation phase
B. hyperpolarisation phase
C. repolarisation phase
D. resting phase

Answer

### Step-by-Step Solution:

1. **Understanding Action Potential**:
- Action potentials are rapid changes in membrane potential that occur in neurons. They consist of several phases: depolarization, repolarization, and hyperpolarization.

2. **Identifying the Phases**:
- **Depolarization Phase**: This is when the membrane potential becomes more positive due to the influx of sodium ions (Na+).
- **Repolarization Phase**: This phase follows depolarization and involves the efflux of potassium ions (K+), returning the membrane potential back toward the resting potential.
- **Hyperpolarization Phase**: This occurs when the membrane potential becomes more negative than the resting potential due to continued K+ efflux.
- **Resting Phase**: This is the stable state of the neuron before an action potential occurs.

3. **Defining Relative Refractory Period**:
- The relative refractory period is the time following an action potential during which a neuron can fire again, but it requires a stronger stimulus than usual. This period occurs after the repolarization phase and can extend into the hyperpolarization phase.

4. **Analyzing the Options**:
- **Depolarization Phase**: Not correct, as this is when the action potential is being generated.
- **Hyperpolarization Phase**: This is when the membrane potential is more negative than the resting potential, but it is not the correct answer for the relative refractory period.
- **Repolarization Phase**: This is when the relative refractory period begins, as the neuron is returning to its resting state but is still not fully ready to fire again.
- **Resting Phase**: This is when the neuron is at its resting potential and is not in a refractory state.

5. **Conclusion**:
- The relative refractory period occurs during the **Repolarization Phase**. This is the time when the neuron is transitioning back to its resting state and can potentially fire again with a stronger stimulus.

### Final Answer:
The relative refractory period occurs during the **Repolarization Phase**.

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