The action potential is determined largely by

Options

A. Influx of `Na^(+)`
B. Effux of `Na^(+)`
C. Influx of `K^(+)`
D. Efflux of `K^(+)`

Answer

**Step-by-Step Solution:**

1. **Understanding Action Potential**: Action potential is a rapid change in the membrane potential of a neuron that occurs when it is stimulated. It is essential for the transmission of nerve impulses.

2. **Resting Membrane Potential**: In a resting neuron, there is a difference in charge across the membrane, known as the resting membrane potential, which is typically around -70 millivolts. This state is maintained by the sodium-potassium pump.

3. **Role of Sodium-Potassium Pump**: The sodium-potassium pump actively transports 3 sodium ions out of the neuron and 2 potassium ions into the neuron. This creates a higher concentration of sodium outside the neuron and a higher concentration of potassium inside.

4. **Stimulus and Depolarization**: When a neuron is stimulated, voltage-gated sodium channels in the axon membrane open. This allows sodium ions to flow into the neuron, leading to depolarization.

5. **Influx of Sodium Ions**: The influx of sodium ions is the primary factor that determines the action potential. As sodium enters the neuron, it causes the inside of the neuron to become more positive, which is the key event in generating an action potential.

6. **Conclusion**: Therefore, the action potential is largely determined by the influx of sodium ions into the neuron.

**Final Answer**: The action potential is determined largely by the influx of sodium ions.

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