7/8/2020 PhysioEx Exercise 6 Activity 5 PhysioEx Lab Report Exercise 6: Cardiovascular Physiology Activity 5: Examining the Eﬀects of Various Ions on Heart Rate Name: Date: 8 July 2020 Pre-lab Quiz Results You scored 100% by answering 4 out of 4 questions correctly. 1 Which organelle in the cardiac muscle cell stores calcium? You correctly answered: sarcoplasmic reticulum. 2 Verapamil is a calcium-channel blocker. Its eﬀects could be described as You correctly answered: negative chronotropic and negative inotropic. 3 When the cardiac muscle cell is at rest, where is most of the potassium found? You correctly answered: in the cytosol. 4 Resting cardiac muscle cells are most permeable to You correctly answered: potassium. Experiment Results Predict Questions 1 Predict Question 1: Because calcium-channel blockers are negative chronotropic and negative inotropic, what eﬀect do you think increasing the concentration of calcium will have on heart rate? Your answer: positive chronotropic, positive inotropic. 2 Predict Question 2: Excess potassium outside of the cardiac cell decreases the resting potential of the plasma membrane, thus decreasing the force of contraction. What eﬀect (if any) do you think it will initially have on heart rate? Your answer: decrease heart rate. Stop & Think Question Where in the cardiac muscle cell is most of the sodium normally found? 1/4 7/8/2020 PhysioEx Exercise 6 Activity 5 You correctly answered: outside of the cell. Experiment Data Solution ---- Heart Rate (beats/min) 59 Calcium 69 Sodium ~34 Potassium ~28 2/4 7/8/2020 PhysioEx Exercise 6 Activity 5 Post-lab Quiz Results You scored 100% by answering 4 out of 4 questions correctly. 1 The addition of most of the ions resulted in You correctly answered: an erratic, decreased heart rate. 2 The eﬀect of potassium on the heart is You correctly answered: negative chronotropic, negative inotropic. 3 The ion that had the most pronounced eﬀect on heart rate was You correctly answered: potassium. 4 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. Review Sheet Results 1 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: Increasing the calcium ions increased both the heart rate and the force of contraction. 2 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? 3/4