Action Potential Phases

Review Question 1: Action Potential

Phases of Action Potential

Resting Phase

• Voltage: -70 mV
• Description of Events: Leakage channels help bring charge back to resting. Na+/K+ pump helps return ions to their original positions.
• Charge: -70

Depolarization Phase

• Voltage: +40 mV
• Description of Events: Na+ moves into cell and cell becomes more positive, fails to close when it gets to zero, and an overshoot causes a positive charge.
• Charge: +40

Repolarization Phase

• Voltage: -70 mV
• Description of Events: Na+ channel closes, K+ channel opens (K+ leaves the cell).
• Charge: -70

Hyperpolarization Phase

• Voltage: -80/90 mV
• Description of Events: Another overshoot occurs, K+ channels close
• Charge: -80

Return to Resting Phase

• Voltage: -70 mV
• Description of Events: More Na+ out and more K+ in to cell leading to negative charge overall
• Charge: +40

Additional Information

• Threshold: -55 mV

• Failed Initiations

Timeline

• The action potential is displayed over Time (ms) 1-5 on a graph