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Questions and Answers
What is the primary difference in how action potentials propagate along unmyelinated and myelinated axons?
What is the primary difference in how action potentials propagate along unmyelinated and myelinated axons?
- Action potential propagation in unmyelinated axons is bidirectional, whereas in myelinated axons it is unidirectional.
- Myelinated axons experience a slower propagation speed due to the myelin sheath, whereas unmyelinated axons have faster conduction.
- Unmyelinated axons transmit action potentials using saltatory propagation, while myelinated axons use continuous propagation.
- Action potentials in myelinated axons jump from node to node, and action potentials in unmyelinated axons travel along the entire axon membrane. (correct)
During the peak of an action potential, what is the electrical charge of the membrane potential?
During the peak of an action potential, what is the electrical charge of the membrane potential?
- The membrane potential becomes strongly negative
- The membrane potential becomes neutral
- The membrane potential becomes positive (correct)
- The membrane potential remains unchanged
Why does an action potential propagate in only one direction along the axon?
Why does an action potential propagate in only one direction along the axon?
- The direction of the local current influences the direction of propagation
- The myelin sheath blocks backward propagation.
- The potassium ion concentration gradients prevent backward propagation.
- The refractory period of the previous segment prevents backward propagation. (correct)
Why can't the axon hillock generate an action potential?
Why can't the axon hillock generate an action potential?
What role do local currents play in the propagation of the action potential?
What role do local currents play in the propagation of the action potential?
What is the speed of action potential propagation with continuous propagation?
What is the speed of action potential propagation with continuous propagation?
Where does the action potential initiate?
Where does the action potential initiate?
What is the main purpose of the myelin sheath in myelinated axons?
What is the main purpose of the myelin sheath in myelinated axons?
Flashcards
Action potential propagation
Action potential propagation
The process of an action potential traveling along the entire membrane surface of an axon, starting at the axon hillock and moving towards the axon terminal.
Continuous propagation
Continuous propagation
A type of action potential propagation where the electrical signal travels continuously along the entire membrane surface of an axon.
Nodes of Ranvier
Nodes of Ranvier
The segments of an axon that are not covered by myelin, where the action potential can occur.
Saltatory propagation
Saltatory propagation
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Refractory period
Refractory period
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Internode
Internode
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Unidirectional propagation
Unidirectional propagation
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Axon hillock
Axon hillock
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Study Notes
Action Potential Propagation
- Action potentials affect the entire axon membrane, unlike graded potentials that diminish with distance.
- Action potentials begin at the axon's initial segment.
- At the peak, the membrane potential briefly becomes positive.
- Sodium ion movement in the cytosol and extracellular fluid creates a local current, depolarizing adjacent membrane segments.
- This process continues in a chain reaction, propagating the action potential along the axon away from its origin.
- The previous segment's refractory period prevents backward movement.
- This method is called continuous propagation, occurring slowly along unmyelinated axons (about 1 meter/second).
Myelinated Axon Propagation
- Myelinated axons are wrapped in myelin, interrupted by nodes of Ranvier.
- Myelin sheath lipids block ion flow between the nodes.
- Continuous propagation is impossible in myelinated axons.
- Saltatory propagation occurs, where the action potential jumps from node to node.
- This process is much faster than continuous propagation (18 to 140 meters/second).
- The name "saltatory" is derived from the Latin word for "to leap."
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