Nervous system

• What is hyperpolarisation?

  • When the voltage decreases below resting potential (-70) and the axon enters a refractory period
• What is the refractory period?

  • When voltage decreases below resting potential (-70) sodium ion channels close and stops the neurone from reaching another action potential
• Why is the refractory period good?

  • It prevents impulses from merging and becoming harder to process
  • It makes sure impulses only travel in one direction
  • It limits impulses to not overwhelm senses
• How is an action potential reached?


  • When an impulse gives enough energy to increase the voltage of the axon from the resting potential past the threshold potential and open voltage gated sodium channels
• How is resting potential maintained?

  • Sodium potassium pump of sodium ions moving in the axon and potassium ions moving out the axon
• What voltage does the axon peak at?

  • +40mv
• What do voltage gated channels do?

  • Allow for more ions to enter the axon at a specific energy
• What voltage is threshold potential?

  • -55mv
• What is threshold potential?

  • The voltage an axon must reach before an action potential can start (-55mv)
• What is an action potential?

  • When an electrical impulse is sent down the neurone and voltage gated sodium ion channels open
• When do voltage gated sodium ion channels open?

  • At threshold potential -55mv
• What is repolarisation?

  • When voltage gated potassium ion channels open and the axon decreases in voltage
• What is the all or nothing principle?

  • If a stimulus does not exceed threshold potential (-55mv) an action potential will not be reached