Multiple select. Choose all that apply: What is occurring as membrane potential reaches the value of threshold?
Group of answer choices
potassium ions are diffusing out of the cell
the action potential begins
voltage-gated sodium channels open
the membrane has returned to -70 mV
the membrane potential has reached -55 mV
- the action potential begins
- voltage-gated sodium channels open
- the membrane potential has reached -55 mV
The correct options are:
- the action potential begins
- voltage-gated sodium channels open
- the membrane potential has reached -55 mV
To determine which statements are true when the membrane potential reaches the value of the threshold, we need to understand the events that occur during an action potential. Here's a step-by-step explanation to help you figure out the correct answers:
1. Resting Membrane Potential: At rest, the membrane potential is typically around -70 mV.
2. Depolarization: When a stimulus depolarizes the membrane potential to reach the threshold of approximately -55 mV, voltage-gated sodium channels open.
3. Sodium Influx: As the voltage-gated sodium channels open, sodium ions (Na+) rush into the cell, further depolarizing the membrane potential.
4. Action Potential: The depolarization caused by the influx of sodium ions triggers an action potential, which is a rapid change in the membrane potential.
5. Repolarization: After the action potential, repolarization occurs, bringing the membrane potential back to its resting state.
6. Potassium Efflux: During repolarization, voltage-gated potassium channels open, allowing potassium (K+) ions to diffuse out of the cell. This efflux helps restore the membrane potential to its resting state.
Now, let's evaluate each statement based on this information:
- Potassium ions are diffusing out of the cell: This is true. During repolarization, potassium ions diffuse out of the cell, aiding in restoring the resting membrane potential.
- The action potential begins: This is false. The action potential is triggered when the membrane potential reaches the threshold, not at the moment it reaches the threshold.
- Voltage-gated sodium channels open: This is true. When the membrane potential reaches the threshold, voltage-gated sodium channels open, allowing sodium ions to enter the cell and initiate depolarization.
- The membrane has returned to -70 mV: This is false. The membrane potential returns to its resting state (-70 mV) after repolarization, not when it reaches the threshold.
- The membrane potential has reached -55 mV: This is true. The membrane potential must reach the threshold value of -55 mV for an action potential to be initiated and for voltage-gated sodium channels to open.
In summary, the correct answers are:
- Potassium ions are diffusing out of the cell
- Voltage-gated sodium channels open
- The membrane potential has reached -55 mV