nerve impulses

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

  Action potential
• What is the resting potential of an axon?

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

  It becomes positive, then negative again
• What is the maximum voltage reached during an action potential?

  +30 millivolts
• What causes the change in voltage during an action potential?

  Movement of sodium and potassium ions
• What ions are primarily involved in generating an action potential?

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

  Through open and voltage-gated channels
• What is the role of pumps in the axon membrane?

  To return ions to their original positions
• What is the process called that requires energy to move ions against diffusion?

  Active transport
• What happens when a stimulus opens sodium channels?

  Sodium ions diffuse into the cell
• What is the threshold voltage that triggers action potential?

  • 50 millivolts
• What occurs during depolarization?

  Sodium ions rapidly enter the cell
• What happens to the voltage during repolarization?

  The voltage decreases back to resting potential
• What is hyperpolarization?

  When the voltage goes below resting potential
• What happens if the stimulus is too small?

  No action potential is generated
• How does the strength of the stimulus affect the signal?

  It changes the frequency of the signal
• Why do signals travel faster in myelinated neurons?

  They jump between nodes of Ranvier
• What is the term for the conduction method in myelinated neurons?

  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, hyperpolarization
  7. Pumps restore resting potential
• What are the key terms related to nerve impulses?

  • Action potential
  • Resting potential
  • Depolarization
  • Repolarization
  • Hyperpolarization
  • Saltatory conduction
  • Threshold voltage
• What is the significance of the nodes of Ranvier in myelinated neurons?


  • They allow for faster signal transmission
  • Action potentials jump between nodes
  • They prevent sodium ion entry in between nodes
• Describe the motion of sodium and potassium ions during a nerve impulse.

  • Sodium ions enter during depolarization
  • Potassium ions exit during repolarization
  • Pumps restore original ion positions after action potential
• What happens when the threshold voltage is reached?

  • Voltage-gated sodium channels open
  • Rapid influx of sodium ions occurs
  • Action potential is generated