Which of the following contributes to the gradual depolarization to threshold in
ID: 3515328 • Letter: W
Question
Which of the following contributes to the gradual depolarization to threshold in cardiac SA node cells? O eflux of K' through volitage-gated channels O efflux of Ca? through L-type channels O influx of Ca2 through T-type channels O efflux of Na' through L-type channels O efflux of Nat through Funny channels References eBook & Resources Multiple Choice Section: 12.04 Check my work 25. 2.00 points Required information l between SA node action potentials is mainly determined by the steepness of the pacemaker potential as it difts toward threshold True O FalseExplanation / Answer
Answer 1. Efflux of calcium ion through L-type channels contributes to the gradual depolarisation to threshold in cardiac SA node. There are slow and long lasting L-type voltage gated calcium ion on the cardiac cell membrane which are responsible for gradual depolarisation.
Answer 2. The statement given is true. That is the time interval between the SA node action potential is mainly determined by the steepness of the pacemaker potential as it drift towards threshold. More the steepness less will be time interval between two SA node action potential.
Answer 3. The statement is false because the permeability to potassium ion is gradually increasing during the diastolic interval when SA node cell membrane potential are drifting towards threshold. There is outward potassium ion current when diastole occurs. Calcium ion channels are closed and there is opening of potassium ion channels.
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