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Questions and Answers
What initiates the generation of an action potential?
What initiates the generation of an action potential?
How does continuous propagation occur in unmyelinated neurons?
How does continuous propagation occur in unmyelinated neurons?
What is the primary advantage of saltatory propagation in myelinated fibers?
What is the primary advantage of saltatory propagation in myelinated fibers?
What characteristic of action potentials differentiates them from graded potentials?
What characteristic of action potentials differentiates them from graded potentials?
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Which of the following statements about nerve conduction velocity is accurate?
Which of the following statements about nerve conduction velocity is accurate?
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What role do nodes play in the propagation of action potentials in myelinated fibers?
What role do nodes play in the propagation of action potentials in myelinated fibers?
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In what way do graded potentials differ in response to stimuli compared to action potentials?
In what way do graded potentials differ in response to stimuli compared to action potentials?
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What condition primarily affects the myelinated fibers in relation to their insulating sheath?
What condition primarily affects the myelinated fibers in relation to their insulating sheath?
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Study Notes
Neuronal Physiology - Action Potential Propagation
- Action potentials are produced by a graded potential exceeding a threshold
- They propagate along the axon surface to the nerve terminal and synapse
- Action potentials are electrical impulses and frequency signals
- Synaptic activity involves the transmission of information between neurons at synapses
Action Potential Propagation (Unmyelinated Nerves)
- Action potentials are propagated due to local currents reinforcing signal activation of voltage-gated sodium channels
- A new action potential is generated sequentially along the axon
- This method of propagation is relatively slow
Myelinated Fibers
- Myelin acts as an insulator, restricting membrane potential to the nodes of Ranvier
- Ions can only cross the membrane at these nodes
- Conditions like Multiple Sclerosis and Guillain Barré syndrome can affect myelin
Saltatory Propagation
- In myelinated axons, action potentials "jump" from node to node (saltatory = jumping)
- Local currents rapidly propagate between nodes
- This method of propagation is faster than continuous propagation
- Less energy is used compared to continuous propagation because fewer ions cross the membrane
Nerve Conduction Velocity
- Nerve conduction velocity is influenced by the nerve type, diameter, and myelination
- Larger diameter axons and myelinated axons generally have faster conduction velocities
- Somatic motor fibers (large diameter, myelinated) have very fast velocity (80-120 m/sec)
- Sensory C fibers (small diameter, unmyelinated) have a slower velocity (0.5-2.0 m/sec)
Summary of Graded vs Action Potentials
| Feature | Graded Potentials | Action Potentials |
|---|---|---|
| Depolarization/Hyperpolarization | Yes | Only depolarizing |
| Threshold Level | No | Yes |
| Amplitude | Varies with stimulus intensity | All-or-none; fixed amplitude |
| Spread | Passive; decreases with distance | Propagated along the entire membrane |
| Summation | Possible | Not possible |
| Refractory Period | No | Yes |
| Location | Most plasma membranes | Excitable membranes (neurons and muscle cells) |
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Description
Test your knowledge on the propagation of action potentials in both unmyelinated and myelinated nerves. This quiz covers key concepts such as graded potentials, local currents, and the role of myelin in nerve signal transmission. Assess your understanding of synaptic activity and related pathologies.
