the stages of an action potential

• what is the first stage in an action potential?

  The membrane starts in the resting state, polarised with the inside of the cell being -60 mV. There is a higher concentration of sodium ions outside of the cell than the inside, there is a higher concentration of potassium ions than the outside.
• What is the second stage in an action potential?

  sodium ion channels open, and some ions diffuse into the cell
• What is the third stage in an action potential?

  The membrane depolarises, it becomes less negative with respect to the outside and reaches the threshold value of -50 mV.
• What is the fourth step of an action potential?

  Positive feedback causes nearby voltage gates sodium ion channels to open, many ions flood in. As more ions enter, the cell becomes more positively charged in its inside relative to the outside.
• what is the fifth step in an action potential?

  The potential difference across the plasma membrane reaches + 40 mV. the inside of the cell is positive compared to the outside now.
• What is the sixth step in an action potential?

  Sodium ion channels close, and potassium ions open.
• What is the seventh step in an action potential?

  The potassium ions diffuse out fo the cell, this brings the potential difference back to negative- the inside is now negative compared to the outside. This is called repolarisation.
• What is the eighth step in an action potential?

  The potential difference overshoots slightly, this makes the cell hyperpolarised.
• What is the ninth step in an action potential?

  The original potential difference is restored, making it so that the cell returns to the resting state.