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Questions and Answers
Questions and Answers
Why is the staggered activation of voltage-gated sodium and potassium channels crucial for proper action potential propagation?
Why is the staggered activation of voltage-gated sodium and potassium channels crucial for proper action potential propagation?
- To ensure complete overlap, maximizing ion flow.
- To allow sodium ions to exit before potassium ions enter, preventing depolarization.
- To prevent signal disruption by ensuring repolarization follows depolarization. (correct)
- To maintain a constant membrane potential of -85mV.
How does the sodium-potassium pump contribute to the action potential process?
How does the sodium-potassium pump contribute to the action potential process?
- By re-establishing ion gradients to restore the resting membrane potential. (correct)
- By actively conducting potassium ions during the repolarization phase.
- By initiating the depolarization phase through sodium ion influx.
- By directly triggering the opening of voltage-gated channels.
What is the direct effect of Na+ ion diffusion during action potential propagation?
What is the direct effect of Na+ ion diffusion during action potential propagation?
- It decreases the threshold potential in adjacent areas of the membrane.
- It triggers the activation of adjacent voltage-gated sodium channels. (correct)
- It neutralizes the positive feedback loop, ensuring it doesn't continue endlessly.
- It inhibits adjacent voltage-gated sodium channels.
During which stage of crossbridge cycling is ATP crucial, and why?
During which stage of crossbridge cycling is ATP crucial, and why?
What is the primary role of calcium ions in sustaining muscle contraction during repeated action potentials?
What is the primary role of calcium ions in sustaining muscle contraction during repeated action potentials?
How does the refractory period ensure unidirectional action potential movement?
How does the refractory period ensure unidirectional action potential movement?
What is the typical order of events during an action potential?
What is the typical order of events during an action potential?
How does the continued opening of voltage-gated calcium channels affect muscle contraction?
How does the continued opening of voltage-gated calcium channels affect muscle contraction?
Under what condition would rigor mortis primarily occur?
Under what condition would rigor mortis primarily occur?
What is the role of acetylcholine in sustaining muscle contraction (tetanus)?
What is the role of acetylcholine in sustaining muscle contraction (tetanus)?
If voltage-gated sodium channels were permanently open, what would be the likely effect on the neuron's membrane potential?
If voltage-gated sodium channels were permanently open, what would be the likely effect on the neuron's membrane potential?
What prevents the action potential from reversing direction once it has been initiated?
What prevents the action potential from reversing direction once it has been initiated?
How do calcium pumps counteract the effects of voltage-gated calcium channels in muscle cells?
How do calcium pumps counteract the effects of voltage-gated calcium channels in muscle cells?
What would be the most immediate effect of a drug that blocks voltage-gated potassium channels in a neuron?
What would be the most immediate effect of a drug that blocks voltage-gated potassium channels in a neuron?
What is the relationship between action potential frequency and muscle contraction strength?
What is the relationship between action potential frequency and muscle contraction strength?
How does the threshold potential relate to voltage-gated sodium channels?
How does the threshold potential relate to voltage-gated sodium channels?
Which of the following would most likely result in muscle fatigue?
Which of the following would most likely result in muscle fatigue?
How does the positive feedback loop relate to the propagation of the action potential?
How does the positive feedback loop relate to the propagation of the action potential?
What is the role of calcium, specifically, in the cross-bridge cycling process?
What is the role of calcium, specifically, in the cross-bridge cycling process?
Questions and Answers
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Flashcards
Flashcards
Voltage-gated sodium channel activation
Voltage-gated sodium channel activation
Channels open at approximately -55mV, triggering depolarization.
Threshold potential
Threshold potential
The membrane potential at which enough sodium channels open to initiate an action potential, typically around -50 to -55mV.
Sodium channel function
Sodium channel function
These channels conduct Na+ ions, causing rapid depolarization of the cell membrane.
Potassium channel function
Potassium channel function
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Sodium-potassium pump role
Sodium-potassium pump role
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Action potential propagation
Action potential propagation
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Refractory period
Refractory period
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Steps of crossbridge cycling
Steps of crossbridge cycling
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ATP and calcium importance
ATP and calcium importance
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Action potential frequency
Action potential frequency
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Calcium pumps vs. voltage channels
Calcium pumps vs. voltage channels
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Factors for tetanus
Factors for tetanus
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Study Notes
Study Notes
Voltage-Gated Sodium and Potassium Channels
- Voltage-gated sodium channels activate first, around -55mV, initiating depolarization
- The threshold potential, typically around -50 to -55mV, is where enough sodium channels open to trigger an action potential
- Sodium channels conduct Na+ ions, causing rapid depolarization of the membrane
- After about half a millisecond, sodium channels inactivate, and voltage-gated potassium channels open
- Potassium channels conduct K+ ions, leading to repolarization and brief hyperpolarization
- Staggered timing of sodium and potassium channels ensures a proper action potential wave; overlap could disrupt the signal
- The sodium-potassium pump re-establishes ion gradients, bringing the membrane back to -85mV
Action Potential Self-Propagation & Refractory Period
- The action potential moves forward as Na+ ions diffuse, triggering adjacent voltage-gated sodium channels
- This process has a positive feedback loop, ensuring continuous propagation
- The refractory period prevents the action potential from traveling backward, ensuring unidirectional movement
Crossbridge Cycling
- The crossbridge cycling steps include crossbridge formation, power stroke, detachment, and re-cocking
- ATP depletion leads to muscle fatigue
- Calcium depletion causes rigor mortis (muscle seizing)
- ATP is crucial between detachment and re-cocking
- Calcium is necessary for continued cycling
Action Potential Frequency & Calcium Regulation
- Neurons must fire repeated action potentials to sustain muscle contraction
- Calcium pumps sequester calcium
- Voltage-gated channels release calcium transiently
- If channels remain open, calcium levels stay high, prolonging contraction
- High action potential frequency, acetylcholine levels, calcium concentration, and ATP availability are necessary for sustained contraction/tetanus
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