Question

Please help

29. The action potential


a. begins with the membrane’s increased permeability to potassium.

b. returns to resting when the sodium channels open.


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


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


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?


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


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


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


d. Current/depolarization continue to spread directionally along the axon, repeating steps a–c

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


b. The voltage dependence of the potassium channels


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

d. Sufficient “leakiness” of the axons, such that backward propagation of action potentials is prevented


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