Propagation of Action Potentials

• What is the definition of local current in the context of nerves?

  The movement of ions along the neurone due to concentration differences.
• How does local current occur in neurons?

  It occurs due to an increase in ion concentration at one point, causing diffusion away from that region.
• What is saltatory conduction?

  A mechanism of nerve impulse transmission in myelinated neurons.
• How does saltatory conduction work?

  Action potential appears to jump from one node of Ranvier to the next.
• What happens when positive ions arrive at one node during saltatory conduction?

  It depolarizes the second node, triggering another action potential.
• What are the key features of local currents and saltatory conduction?

  • Local currents involve ion movement along the neurone.
  • Caused by concentration differences leading to diffusion.
  • Saltatory conduction occurs in myelinated neurons.
  • Action potentials jump between nodes of Ranvier.
  • Positive ions depolarize subsequent nodes.
• What is the direction of movement for an action potential along a neurone?

  The action potential moves in one direction until it reaches the end of the neurone.
• Why does the action potential not reverse direction?

  Because the concentration of sodium ions behind the action potential is still high.
• What is the process of action potential propagation along a neurone?

  1. Na+ channels open, allowing Na+ to diffuse inside the neurone.
  2. Localized increase in concentration of Na+ inside the neurone occurs.
  3. This increase causes the action potential.
  4. Na+ diffuses along the axon.
  5. Na+ gates that were initially closed open due to Na+ movement, allowing the action potential to move.
• How far apart are the nodes along the neurone?

  The nodes are 1 - 3 mm apart.
• What happens when Na+ channels open in a neurone?

  Na+ diffuses inside the neurone, increasing the concentration of Na+ inside.
• What is the role of Na+ movement in the action potential process?

  Na+ movement causes the action potential and allows it to propagate along the neurone.
• What is the effect of myelination on action potential conduction?

  Myelination increases the rate of action potential conduction.
• What is the term used for the conduction method in myelinated axons?

  Saltatory conduction
• What is the role of the myelin sheath in neurons?

  The myelin sheath insulates the axon to facilitate faster conduction.
• What happens to action potential conduction in unmyelinated axons?

  It occurs at a slower rate compared to myelinated axons.
• How does the presence of nodes of Ranvier affect action potential conduction?

  Nodes of Ranvier allow for faster conduction through saltatory conduction.
• What are the key differences between myelinated and unmyelinated axons in terms of action potential conduction?

  • Myelinated axons conduct action potentials faster due to saltatory conduction.
  • Unmyelinated axons conduct action potentials slower through continuous conduction.
  • Myelinated axons have nodes of Ranvier that facilitate rapid transmission.
• What is the resting potential of a neuron?

  The resting potential is typically around -70 mV.
• What is the significance of action potentials in neurons?

  Action potentials are essential for transmitting signals along neurons.
• What ions are primarily involved in generating action potentials?

  Sodium (Na+) and potassium (K+) ions are primarily involved.
• What is the role of K+ ions during an action potential?

  K+ ions help to repolarize the neuron after depolarization.
• What is the relationship between action potential conduction rates and the presence of myelination?

  Myelination increases action potential conduction rates compared to unmyelinated axons.
• What is the typical resting potential of a neuron?

  • 70 mV
• What is the effect of action potentials on neuron signaling?

  Action potentials enable neurons to communicate signals effectively.
• What is the primary function of the myelin sheath?

  To insulate axons and increase the speed of action potential conduction.
• What is the state of the voltage-gated sodium channels in the resting state of a sector?

  They are closed but in an active state.
• What characterizes the refractory period in a sector?

  The voltage-gated sodium ion channels are closed and inactive.
• How does the impulse travel during the refractory period?

  It only travels in one direction.
• What initiates an action potential in a sector?

  Local depolarizations begin to open voltage-gated sodium channels.
• What is the composition of the myelin sheath?

  It contains myelin, a phospholipid.
• What happens to voltage-gated sodium channels in the sector during action potential propagation?

  They are opened, allowing sodium ions to move.
• What is the role of the myelin sheath in action potential propagation?

  It does not conduct an electric current.
• What is the Node of Ranvier?

  It is a region of unmyelinated nerve cell membrane.
• What occurs at the Node of Ranvier regarding ion movement?

  Voltage-gated ion channels allow Na+ and K+ movement across the membrane.
• How effective are depolarizations of voltage-gated sodium channels?

  They are effective over greater distances between adjacent Nodes of Ranvier.
• What is saltatory conduction in myelinated neurons?

  • The impulse jumps from node to node.
  • It increases the speed of action potential propagation.
  • It occurs at the Nodes of Ranvier.