Action potentials

• What is an action potential in neurons?

  It is a nervous impulse generated by voltage change.
• What is the resting potential of a neuron?

  -70 millivolts
• What causes depolarization in a neuron?

  Increased permeability to sodium ions.
• What happens when the action potential is generated at one node?

  It triggers the next node of Ranvier.
• What maintains the resting potential in a neuron?

  Sodium-potassium pump and potassium ion channels.
• What is the threshold potential for generating an action potential?

  -55 millivolts
• What occurs when the threshold is reached?

  More voltage-gated sodium channels open.
• What is the peak voltage of an action potential?

  +40 millivolts
• What happens during repolarization?

  Potassium ions diffuse out of the axon.
• What is hyperpolarization?

  Voltage drops below resting potential.
• What is the refractory period?

  Time when the neuron cannot fire another action potential.
• Why is the refractory period important?

  It prevents overlapping action potentials.
• How does the all-or-nothing principle work?

  If the threshold is reached, an action potential occurs.
• What happens with larger stimuli?

  Higher frequency of action potentials occurs.
• Why is it important for animals to respond only to significant stimuli?

  To prevent overwhelming their senses.
• What does the action potential graph represent?

  Change over time, not distance.
• What is the role of sodium channels during the refractory period?

  They recover and cannot be opened.
• How does the action potential travel along the axon?

  It travels in one direction due to the refractory period.
• What is the significance of discrete impulses in action potentials?

  They allow detailed processing of information.
• What is the effect of a stimulus that does not reach the threshold?

  No action potential is generated.
• What is the relationship between stimulus intensity and action potential frequency?

  Higher intensity leads to higher frequency.
• Why is it crucial for action potentials to be discrete?

  To accurately identify and process stimuli.
• What is the structure that carries action potentials to surrounding cells?

  Dendrites
• What is the function of the cell body in a neuron?

  Contains organelles for protein and neurotransmitter production
• What is the long conductive fiber in a neuron called?

  Axon
• What is the role of the myelin sheath?

  Acts as an insulator for the axon
• What are the gaps in the myelin sheath called?

  Nodes of Ranvier
• What is resting potential in a neuron?

  Difference in electrical charge when not conducting
• What is the resting potential value in millivolts?

  -70 millivolts
• Why is the resting potential negative?

  More positive ions outside than inside
• How is the resting potential maintained in a neuron?

  Through sodium-potassium pump and ion channels
• What does the sodium-potassium pump do?

  Transports three sodium ions out and two potassium ions in
• What is created by the sodium-potassium pump's activity?

  An electrochemical gradient
• How do potassium ions move in relation to their concentration gradient?

  From high concentration inside to low outside
• Why do sodium ions move into the axon?

  Due to a higher concentration outside than inside
• Why is the cell membrane more permeable to potassium ions?

  More potassium ion channels are present
• What happens to sodium ion channels at high voltage?

  They open to allow sodium ions in
• What are the main components of a myelinated motor neuron?

  • Cell body: Contains organelles
  • Dendrites: Carry action potentials
  • Axon: Conducts nerve impulses
  • Myelin sheath: Insulates axon
  • Nodes of Ranvier: Gaps for action potential generation
• What is the process of maintaining resting potential in a neuron?

  1. Sodium-potassium pump actively transports ions

  • 3 sodium ions out
  • 2 potassium ions in

  1. Creates an electrochemical gradient
  2. Potassium ions diffuse out; sodium ions diffuse in
  3. More potassium channels open than sodium channels
• What is the significance of resting potential in neurons?

  • Essential for generating action potentials
  • Allows neurons to respond to stimuli
  • Maintains electrical charge difference across membrane