2 The ion that had the most pronounced effect on heart rate was You correctly answered: potassium. 3 Ectopic pacemakers can be caused by excessive leakage of potassium into cardiac cells, resulting in pacemakers appearing in abnormal locations in the heart muscle. This hyperkalemia (excess potassium) decreases the resting potential of the cardiac muscle cell. What effect do you think this would have on the force of contraction? You correctly answered: decrease, negative inotropic. 4 Describe the effect that increasing the calcium ions had on the heart in this activity. How well did the results compare with your prediction? Your answer: -increases HR -increases force of contraction. 1
4/6/2020 PhysioEx Exercise 6 Activity 5 4/4 Describe the effect that increasing the potassium ions initially had on the heart in this activity. Relate this to the resting membrane potential of the cardiac muscle cell. How well did the results compare with your prediction? Your answer: -decreases HR, then it makes it erratic -lowers resting membrane potential. 2 Describe how calcium channel blockers are used to treat patients and why? Your answer: -decreased calcium causes both decreased rate of depolarization and decreased force of contraction, and decreased peripheral resistance. 3
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