[PhysioEX Chapter 6 exercise 5] PEX-06-05

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Exercise 6: Cardiovascular Physiology: Activity 5: Examining the Effects of Various Ions on Heart Rate Lab Report

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: b. sarcoplasmic reticulum
2. Verapamil is a calcium-channel blocker. Its effects could be described as
   You correctly answered: d. negative chronotropic and negative inotropic.
3. When the cardiac muscle cell is at rest, where is most of the potassium found?
   You correctly answered: c. in the cytosol
4. Resting cardiac muscle cells are most permeable to
   You correctly answered: b. potassium.

Experiment Results

Predict Question:
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 : a. positive chronotropic, positive inotropic

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 : b. decrease heart rate

Stop & Think Questions:
Where in the cardiac muscle cell is most of the sodium normally found?
You correctly answered: a. outside of the cell

Experiment Data:
Solution Heart Rate
---- 59
Calcium 68
Sodium 34 then erratic
Potassium 28 then erratic

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: c. an erratic heart rate.
2. The effect of potassium on the heart is
   You correctly answered: b. negative chronotropic, negative inotropic.
3. The ion that had the most pronounced effect on heart rate was
   You correctly answered: c. 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: d. 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:
   Because of increasing heart rate and contraction pressure, blood goes faster as predicted.
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?
   Your answer:
   High potassium ions decreases the resting potential and decreases the pressure of contraction as predicted.
3. Describe how calcium channel blockers are used to treat patients and why?
   Your answer:
   In all path of action potential,they block the movement of calcium through the channels. Decreased calcium causes
   decreased peripheral resistance, decreased heart rate and decreased pressure of contraction.