Nerve Impulse

• What is the electrical signal called that travels down a neuron?

  Action potential
• How does the voltage change as the action potential travels down the axon?

  It becomes positive inside and negative outside
• What is the resting potential of an axon?

  -70 millivolts
• What is the maximum voltage reached during an action potential?

  +30 millivolts
• What happens to the voltage after it reaches +30 millivolts?

  It falls to about -90 millivolts
• What causes the change in voltage during an action potential?

  Movement of sodium and potassium ions
• How do sodium and potassium ions move through the axon membrane?

  Through open gates and pumps
• What are voltage-gated channels?

  Channels that open at specific voltage levels
• What is the role of ATP in ion movement?

  It provides energy for active transport
• What is depolarization in the context of nerve impulses?

  When sodium ions rush into the cell
• What happens during repolarization?

  Potassium ions leave the cell
• What is hyperpolarization?

  When the voltage goes below -70 millivolts
• How does the strength of a stimulus affect the action potential?

  It changes the frequency of the signal
• What is saltatory conduction?

  Signal jumps between nodes of Ranvier
• What is the function of the myelin sheath?

  It insulates the axon
• Why do signals travel faster in myelinated neurons?

  Because of saltatory conduction
• What are the steps of an action potential?

  1. Resting potential at -70 mV
  2. Stimulus opens sodium channels
  3. Sodium ions enter, depolarization occurs
  4. Voltage reaches +30 mV
  5. Potassium channels open, repolarization occurs
  6. Voltage drops to -90 mV
  7. Pumps restore resting potential
• What are the key terms related to nerve impulses?

  • Action potential
  • Resting potential
  • Depolarization
  • Repolarization
  • Hyperpolarization
  • Saltatory conduction
  • Voltage-gated channels
• What happens if a stimulus is too small?

  • No action potential generated
  • Voltage does not reach threshold
• How do sodium and potassium ions contribute to nerve impulses?

  • Sodium ions cause depolarization
  • Potassium ions cause repolarization
• What is the role of pumps in the axon?

  • Restore ion concentrations
  • Require ATP for active transport
• How does the action potential graph look?

  • Starts at -70 mV
  • Rises to +30 mV
  • Falls to -90 mV
  • Returns to -70 mV