The Resting Potential and the Action Potential · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

The spark that travels the nerve

Science · The Human Body · ages 17-18
Name ______________________   Date ____________

  1. What does the sodium potassium pump do?

    • Pulls sodium in and pushes potassium out for free
    • Opens voltage-gated channels
    • Pushes three sodium out and pulls two potassium in, using ATP

  2. What is the resting voltage of a neurone?

    • About zero millivolts
    • About minus 70 millivolts, negative inside
    • About plus 70 millivolts

  3. Repolarisation is caused by sodium rushing into the cell.

    Circle one:   True   False

  4. Which channels drive the rise and which drive the fall?

    • Chemically gated channels drive both
    • Potassium channels drive the rise, sodium the fall
    • Voltage-gated sodium drives the rise, voltage-gated potassium the fall

  5. Put the spike in order.

    • Depolarisation, repolarisation, hyperpolarisation
    • Repolarisation, depolarisation, hyperpolarisation
    • Hyperpolarisation, depolarisation, repolarisation

  6. Why does the trace dip below resting voltage?

    • Sodium channels reopen early
    • Potassium keeps leaving briefly before the pump restores balance
    • The pump reverses direction

  7. A student says hyperpolarisation is sodium rushing in. What is wrong?

    • The rise is sodium in, while the dip comes from potassium still leaving
    • Hyperpolarisation needs no ions at all
    • Sodium never crosses the membrane

  8. A poison stops the sodium potassium pump. What happens to the resting potential over time?

    • It fades as the gradients run down
    • It doubles in size
    • Nothing changes at all
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Answer key

For grown-ups. Fold this page away before handing over the rest.

The spark that travels the nerve W1-mt_0sh4w30ocz-s1

  1. Pushes three sodium out and pulls two potassium in, using ATP · It trades three sodium for two potassium at the cost of ATP.
  2. About minus 70 millivolts, negative inside · Resting means negative inside, near minus 70 millivolts.
  3. False · Repolarisation is potassium leaving, not sodium entering.
  4. Voltage-gated sodium drives the rise, voltage-gated potassium the fall · Sodium in lifts the trace, potassium out drops it.
  5. Depolarisation, repolarisation, hyperpolarisation · Rise first, fall next, dip below last.
  6. Potassium keeps leaving briefly before the pump restores balance · Extra potassium outflow overshoots the resting point.
  7. The rise is sodium in, while the dip comes from potassium still leaving · Sodium entry lifts the trace. The dip is potassium outflow.
  8. It fades as the gradients run down · With no pumping, leaks erase the gradients that hold the voltage.
Worksheet · LightMySky