BIOL 1201 Chapter : Axon Potential

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azuremammoth471

15 Mar 2019

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Axon potential: only triggered in the axon, this is the nerve impulse, all or nothing response (either have it or don"t) Sodium and potassium voltage-gated ion channels are closed. Smallest (depolarizing) voltage required to elicit an action potential. Sodium channels open, influx of sodium: potassium channels are closed. Falling phase of the action potential: potassium channels open. Refractory period: hyperpolarization of the nerve membrane, cannot generate another nerve impulse during this period. Undershoot phase: refractory period (cannot generate another nerve impulse, hyperpolarization, potassium channel still open, potassium efflux. Sodium channel closed: gate closes more slowly than sodium channel. Cells insulating the axons of vertebrates in the pns. The leakage of ions across the plasma membrane is countered by na-k atpase (na-k pump). Na-k atpase is an example of active transport. Hyperpolarize a cell- interior of the cell becomes more negative. Graded potentials: result in hyperpolarization or depolarization.

Related Questions

What would be most strongly affected by a drug that inhibited the opening of voltage-gated potassium channels (also known as delayed rectifiers)?

A. Falling phase of an action potential

B. Rising phase of an action potential

C. Resting membrane potential

D. Threshold for an action potential

Why does the voltage during the undershoot phase of the action potential become more negative than the resting membrane potential?

A. During the undershoot potassium ions are flowing into the cell due to the reversal of the potassium concentration gradient occurring during the action potential

B. The undershoot phase results from a delay in the activation of sodium channels, resulting in some sodium channels being open after the voltage-gated potassium channels have closed. C. The potassium conductance is higher during the undershoot than during the resting membrane potential.

D. The concentration gradient for potassium has been reversed as a result of the action potential, and the undershoot phase lasts until this the concentration gradient is restored.

silverdinosaur935

1.A stronger stimulus to a neuron results in ________.

A. larger voltage changes in graded potentials and greater frequency of action potentials produced in response

B. greater frequency of graded potentials and larger voltage changes in the action potentials produced in response

C. larger voltage changes in the graded potentials, but no changes in action potentials

D. larger voltage changes in both graded and action potentials

E. larger voltage changes in graded potentials but smaller action potentials

2. Why is it more difficult to fire an action potential when the interval between stimuli decreases?

A. because sodium is flowing out of the cell

B. because potassium is flowing into the cell

C. because some sodium channels may still be in an inactivated state

D. because chloride is flowing into the cell

E. because chloride is flowing out of the cell

3. As an action potential zips down an axon,

A. voltage gated potassium channels open first followed by voltage-dependent sodium channels

B. voltage- gated sodium channels ahead of the wave and not yet activated are influenced by the depolarizing electrical field of other nearby sodium channels

C. voltage-gated potassium channels ahead of the wave and not yet activated are influenced by the depolarizing electrical field of nearby sodium channels

D. leak channels are opened by the wave of electricity passing along the axon

E. B and C

Please help

29. The action potentialâ¨

a. begins with the membraneâs increased permeability to potassium.

b. returns to resting when the sodium channels open.â¨

c. can be triggered by opening of ligand gated Na and K channels.â¨

d. involves voltage-gated Chloride channels in the membrane.â¨

e. can be triggered by opening of voltage gated Na+ and K+ channels.

30. Which of the following is not a step in the propagation of action potentials?

â¨a. Sufficient local inward current causes the axon to reach threshold.

â¨b. Local depolarization/inward current spreads to adjacent axonal regions.â¨

c. Adjacent regions eventually reach threshold and exhibit an action potential waveform.

â¨d. Current/depolarization continue to spread directionally along the axon, repeating steps aâc

e. All of the above are steps contributing to the propagation of action potentials.

31. Which of the following is important for the unidirectional propagation of action potentials?

a. The voltage dependence of the sodium channels

â¨b. The voltage dependence of the potassium channels

â¨c. The presence of a refractory period at a location where an action potential has just fired

d. Sufficient âleakinessâ of the axons, such that backward propagation of action potentials is prevented

â¨e. The capacity of axons to function as perfect insulators and prevent current leakage and backpropagation

BIOL 1201 Chapter : Axon Potential

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