6.3.2.3 Axon

• What are the nodes of Ranvier?

  Gaps in the myelin sheath along the axon
• What are the key characteristics of an axon?

  • Long and slender extension of a neuron
  • Carries nerve impulses away from the cell body
  • Functions like an electrical wire
• What are the key structural features of the axon?

  1. Long cylindrical shape
  2. Outer membrane with ion channels
  3. Interrupted myelin covering
  4. Exposed nodes at regular intervals
• What happens during depolarization in the axon?

  Sodium channels open, creating a positive charge
• What do the nodes of Ranvier expose?

  The axon membrane to extracellular fluid
• What is the purpose of the myelin sheath around an axon?

  • Increases the speed of electrical impulse transmission (nerve impulse propagation)
  • Provides insulation and protection for the axon
  • Allows for faster, more efficient communication between neurons
• What does the image in the study material illustrate?

  How electrical waves move along the axon
• What is the definition of an axon?

  A long, slender extension of a neuron
• What is the purpose of the myelin sheath around an axon?

  • Increases the speed of electrical impulse transmission (nerve impulse propagation)
  • Provides insulation and protection for the axon
  • Allows for faster, more efficient communication between neurons
• How does the wave of depolarization move along the axon?

  It jumps between nodes of Ranvier due to myelin insulation
• What is the term used to describe the axon when the myelin sheath has been removed?

  Demyelinated axon
• What are the main components of a neuron?

  • Cell body (soma)
  • Dendrites
  • Axon
  • Schwann cells (myelin sheath)
• How does an axon function similarly to an electrical wire?

  It transmits electrical signals across the body
• How does the structure of a neuron relate to its function?

  • Dendrites receive input signals
  • Cell body integrates signals
  • Axon transmits output signals
  • Myelin sheath insulates the axon to allow for faster signal transmission
• What is the function of the myelin sheath?

  It insulates and speeds up signal transmission
• What is the term used to describe the axon when the myelin sheath has been removed?

  Demyelinated axon
• What is the effect of myelin insulation on nerve impulse transmission?

  Increases speed of impulse transmission
• How do the refractory periods shown in the image affect the propagation of the action potential?

  • The absolute refractory period prevents the neuron from firing another action potential immediately
  • The relative refractory period makes it harder for the neuron to fire another action potential
  • This ensures the action potential propagates in one direction along the axon
• What is the term used to describe the axon when it is covered in a myelin sheath?

  Myelinated axon
• What is the significance of the nodes of Ranvier in nerve impulse transmission?

  • Allow action potentials to jump along the axon
  • Increase the speed of nerve impulse transmission
  • Result from myelin insulation of the axon
• How do the diagrams illustrate the difference between a myelinated and demyelinated axon?

  The myelinated axon has a continuous myelin sheath, while the demyelinated axon has gaps in the myelin sheath
• What are the key differences between myelinated and demyelinated axons?

  • Myelinated axons have continuous insulation
  • Demyelinated axons have exposed patches
  • Nodes of Ranvier are regularly spaced in myelinated axons
• What is a myelinated axon covered with?

  A complete myelin sheath
• How do the refractory periods shown in the image help ensure the action potential propagates in one direction along the axon?

  The refractory periods prevent the neuron from firing another action potential in the opposite direction
• What are the gaps between myelin sections called?

  Nodes of Ranvier
• How do myelinated axons propagate signals?

  Through saltatory conduction between nodes of Ranvier
• What is the purpose of the myelin sheath shown in the image?

  To insulate the axon and increase the speed of action potential propagation
• What type of conduction do unmyelinated axons use?

  Continuous conduction
• What is the term used to describe the axon when it is covered in a myelin sheath?

  Myelinated axon
• What are the main features that differentiate myelinated and unmyelinated axons?

  • Signal Path:
  • Myelinated: Jumps between nodes
  • Unmyelinated: Travels continuously
  • Insulation:
  • Myelinated: Myelin sheath present
  • Unmyelinated: Myelin sheath absent
  • Speed:
  • Myelinated: Faster
  • Unmyelinated: Slower
• What is the primary function of an axon?

  To carry nerve impulses away from the cell body
• Why do the channels in the axon membrane become depolarized and repolarized during an action potential?

  Because the opening and closing of ion channels changes the charge across the membrane
• What regions are depicted as depolarized in the image?

  Green regions indicating positive charge areas
• What are the three stages of action potential propagation in the axon?

  1. Resting potential: Negative charge maintained inside
  2. Depolarization: Sodium channels open, positive charge created
  3. Propagation: Wave of depolarization moves along axon
• What is present in myelinated axons that is absent in unmyelinated axons?

  Myelin sheath
• What covers the axon?

  Myelin sheath
• How does a demyelinated axon differ from a myelinated axon?

  It lacks or has damaged myelin covering
• How does the speed of signal transmission compare between myelinated and unmyelinated axons?

  Myelinated axons are faster
• What is the role of the axon in nerve impulse transmission?

  Transmits nerve impulses via action potential
• What is the function of the nodes of Ranvier?

  They allow for saltatory conduction of the action potential along the axon