Which of the following statements is TRUE concerning depolarization of a SA nodal cell?
a. The cell will not depolarize until it receives sympathetic stimulation
b. The pacemaker potential is caused by Ca2+ entering the cell via L-type Ca2+ channels.
c. The pacemaker potential is slower in achieving threshold when acetylcholine is applied to the SA node cells.
d. During depolarization there is a gradually increasing permeability to K+.
e. The slope of the depolarization is decreased when norepinephrine is applied to the SA node cells
Answer: c. The pacemaker potential is slower in achieving threshold when acetylcholine is applied to the SA node cells.
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