Action potential mechanisms, synaptic transmission, and sensory receptor physiology tested on USMLE Step 1.
35 cards · basic cards · AI-written, checked twice. Edit anything.
- What is the typical resting membrane potential of a neuron?
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About -70 mV- Which ion channels open first during the depolarization phase of an action potential?
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Voltage-gated Na+ channels- What two events cause repolarization after an action potential?
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Voltage-gated Na+ channels inactivate and voltage-gated K+ channels open- What is the threshold potential?
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The membrane voltage at which enough Na+ channels open to make depolarization self-sustaining, triggering an action potential- What happens if a stimulus arrives during the absolute refractory period?
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No new action potential can be generated, no matter how strong the stimulus- What is the relative refractory period?
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A period after the absolute refractory period when only a stronger-than-normal stimulus can trigger another action potential- What causes the absolute refractory period?
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Inactivation of voltage-gated Na+ channels- Using the Nernst equation, what is the approximate equilibrium potential for Na+ in a neuron?
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About +60 mV- Using the Nernst equation, what is the approximate equilibrium potential for K+ in a neuron?
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About -90 mV- What does the Na+/K+ ATPase pump transport per cycle?
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3 Na+ out of the cell and 2 K+ into the cell- How does myelination increase nerve conduction velocity?
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It enables saltatory conduction, where the action potential jumps between nodes of Ranvier- Where are voltage-gated Na+ channels concentrated on a myelinated axon?
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At the nodes of Ranvier- How does increasing axon diameter affect conduction velocity?
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It increases conduction velocity by reducing internal (axoplasmic) resistance- How does hyperkalemia affect the resting membrane potential of excitable cells?
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It depolarizes the resting membrane potential, making it less negative- What is the mechanism of action of local anesthetics such as lidocaine?
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They block voltage-gated Na+ channels, preventing action potential propagation
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