Questions and Answers
What initiates the rapid depolarization during the action potential?
Which phase of the action potential is characterized by the influx of Na+ ions?
What characterizes the negative after-potential phase of the action potential?
What occurs during the ascending limb of the spike potential?
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Which of the following best describes the mechanism of repolarization during the action potential?
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What is the outcome of the action potential's overshoot phase?
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During what interval does the impulse travel toward the recording electrode?
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Which of the following statements about the action potential is false?
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What primarily initiates the depolarization phase of the action potential in neurons?
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Which of the following phases is characterized by the rapid decline of membrane potential after reaching its peak during an action potential?
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What is the key ionic change that occurs during the repolarization phase of an action potential?
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What defines the after potential following an action potential?
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During the action potential, what generally triggers the opening of voltage-gated Na+ channels?
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How do the Na+/K+ pumps contribute to the overall action potential process?
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What role does the presence of negatively charged proteins inside the cell play in resting membrane potential?
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Which event marks the peak of the action potential?
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What primarily triggers repolarization in a neuron's action potential?
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At what membrane potential do the sodium channels begin to activate during depolarization?
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What role does the Na-K pump play during the action potential?
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What occurs during the after potential phase after a neuron's action potential?
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How does sodium influx specifically affect the membrane potential during depolarization?
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Which component of the Na+ channel is responsible for its voltage-gated nature?
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What characterizes the spike potential phase of an action potential?
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What primarily influences the duration of small waves during after potentials?
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Study Notes
Threshold Stimulus and Action Potential
- Action potential can be recorded using cathode ray oscilloscope with microelectrodes; one is inserted into the nerve, and the other is positioned on its outer surface.
- Stimulating the nerve generates a stimulus artifact due to current leakage, followed by a latent period representing the time taken for the impulse to reach the recording electrode.
Phases of Action Potential
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Spike Potential consists of:
- Depolarization Stage: Upward shift in membrane potential due to Na+ influx.
- Repolarization Stage: Downward shift as K+ ions exit the cell.
- Negative After-Potential: Occurs after repolarization.
- Positive After-Potential: The brief period of elevated voltage following action.
Components of Action Potential
- Spike Potential Duration: Occurs over a short span of 0.5 - 1 msec in myelinated fibers.
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Ionic Changes during Depolarization:
- Ascending Limb: Na+ influx changes membrane potential from -70 mV (resting) to -55 mV (threshold).
- Rapid Na+ influx at the threshold leads to overshoot, pushing membrane potential to +35 mV, indicating reversal of polarity.
Mechanism of Ionic Movement
- Repolarization: About 70% of the repolarization process involves K+ efflux following the rapid opening of voltage-sensitive K+ channels after Na+ channels close.
Ion Channel Dynamics
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Na+ Channels:
- Composed of an activation gate on the outer membrane and an inactivation gate on the inner side.
- Voltage-gated; their opening and closure depend on the membrane potential.
Redistribution of Ions
- Na+/K+ pump restores resting membrane potential by actively transporting Na+ out and K+ into the cell.
After Potentials
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Types of After Potentials:
- Negative After Potential: Occurs upon reaching 70% of repolarization; resting potential is slowly restored.
Resting Membrane Potential (RMP)
- Definition: The voltage difference across the cell membrane; in nerves, it is approximately -70 mV, maintained by K+ leak channels and negatively charged proteins within cells.
- Na+/K+ pump helps in correcting disturbances to the resting membrane potential.
Definition of Action Potential
- Action potential is defined as rapid changes in membrane potential during a threshold or suprathreshold stimulus, essential for the propagation of nerve impulses along the neuron.
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Description
This quiz focuses on the recording of action potentials in neurophysiology. It covers the methods used to measure action potentials with cathode ray oscilloscopes and microelectrodes, as well as the phases of action potential. Test your understanding of these fundamental concepts in nerve stimulation and signal recording.
