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Questions and Answers
What happens during the rising phase of the action potential?
What happens during the rising phase of the action potential?
Threshold is crossed, membrane potential increases, Na⁺ channels open, Na⁺ rushes in, cytosol becomes positive, action potential is triggered.
Describe the falling phase of the action potential.
Describe the falling phase of the action potential.
Na⁺ channels become inactivated, K⁺ channels open, K⁺ leaves the cell, cytosol becomes more negative.
What occurs during hyperpolarization/undershoot phase of the action potential?
What occurs during hyperpolarization/undershoot phase of the action potential?
Voltage-gated K⁺ channels remain open, K⁺ continues to leave the cell, membrane becomes more negative than the resting potential.
Explain the All-or-none Law in relation to action potentials.
Explain the All-or-none Law in relation to action potentials.
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What is the refractory period in the context of action potentials?
What is the refractory period in the context of action potentials?
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How do voltage-gated Na⁺ channels contribute to the speed of impulse conduction?
How do voltage-gated Na⁺ channels contribute to the speed of impulse conduction?
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What is an action potential?
What is an action potential?
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What are the two types of voltage-gated channels involved in generating an action potential?
What are the two types of voltage-gated channels involved in generating an action potential?
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What happens during depolarization in the context of an action potential?
What happens during depolarization in the context of an action potential?
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Describe the resting state of a neuron.
Describe the resting state of a neuron.
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What is the threshold membrane potential that triggers an action potential?
What is the threshold membrane potential that triggers an action potential?
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What is the role of ligand-gated channels in neurotransmission?
What is the role of ligand-gated channels in neurotransmission?
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What is the role of Na+ in the propagation of action potentials?
What is the role of Na+ in the propagation of action potentials?
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Why can't an action potential induce another action potential in the previous region/behind?
Why can't an action potential induce another action potential in the previous region/behind?
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Describe how an action potential is transmitted along an axon.
Describe how an action potential is transmitted along an axon.
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What happens as an action potential progresses along the axon?
What happens as an action potential progresses along the axon?
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Explain the concept of wave of depolarization in relation to action potentials.
Explain the concept of wave of depolarization in relation to action potentials.
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How does the termination of neurotransmission occur?
How does the termination of neurotransmission occur?
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Study Notes
Action Potential
- An action potential is a nerve impulse that travels rapidly along an axon in response to stimuli, involving changes in membrane potential from -70 mV to +40 mV.
- It involves the opening and closing of specific voltage-gated channels: voltage-gated sodium ion (Na⁺) channels and voltage-gated potassium ion (K⁺) channels.
Phases of Action Potential
- Resting state: Most voltage-gated sodium (Na+) and potassium (K+) channels are closed, maintaining a resting potential of around -70 mV.
- Depolarization: A stimulus opens some voltage-gated Na⁺ channels, allowing Na⁺ to diffuse into the cell and depolarize the membrane.
- Rising phase: The membrane potential increases as more voltage-gated Na⁺ channels open, and Na⁺ rushes into the cytosol, making it more positive relative to the outside.
- Falling phase: Most voltage-gated Na⁺ channels become inactivated, and most voltage-gated K⁺ channels open, allowing K⁺ to leave the cell and making the cytosol more negative than the outside.
- Hyperpolarization/Undershoot: The slow-acting voltage-gated K⁺ gates remain open, allowing K⁺ to continue moving out of the cell, making the membrane more negative (-80 mV) than the resting potential.
Propagation of Action Potentials
- An action potential in one region can depolarize the next region to threshold, producing a new action potential in the forward direction.
- The action potential is regenerated along the axon as a wave of depolarization that travels down the axon.
- As an action potential progresses along the axon, repolarization occurs quickly behind it.
Characteristics of an Impulse
- All-or-none Law:
- Refractory Period:
- Speed of Conduction:
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Description
Test your knowledge on action potential, a nerve impulse that travels rapidly along an axon in response to stimuli. Learn about the changes in membrane potential across the axon and the role of voltage-gated sodium and potassium ion channels.