PhysioEx Lab 6 Activity 1

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Dallas County Community College *

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2402

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Biology

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Apr 3, 2024

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3/17/24, 4:05 PM PhysioEx Exercise 6 Activity 1 PhysioEx Lab Report Exercise 6: Cardiovascular Physiology Activity 1: Investigating the Refractory Period of Cardiac Muscle Date: 17 March 2024 Session ID: session-939f60f5-b2df-d546-2520-215ac073a391 Pre-lab Quiz Results You scored 100% by answering 4 out of 4 questions correctly. 1 The cardiac muscle is capable of which of the following? You correctly answered: autorhythmicity. 2 Phase 2 of the cardiac action potential, when the calcium channels remain open and potassium channels are closed, is called the You correctly answered: plateau phase. 3 Which of the following is true of the cardiac action potential? You correctly answered: The cardiac action potential is longer than the skeletal muscle action potential. 4 The main anatomical difference between the frog heart and the human heart is that the frog heart has You correctly answered: a single, fused ventricle. Experiment Results Predict Questions 1 Predict Question 1: When you increase the frequency of the stimulation, what do you think will happen to the amplitude (height) of the ventricular systole wave? Your answer: The amplitude will increase. 2 Predict Question 2: If you deliver multiple stimuli (20 stimuli per second) to the heart, what do you think will happen? Your answer: neither wave summation nor tetanus. Stop & Think Questions 1 Watch the contractile activity from the frog heart on the oscilloscope. Enter the number of ventricular contractions per minute (from the heart rate display). You answered: 62 beats/min. 2 Which of the following statements about the contractile activity is true? You correctly answered: The smaller waves represent the contraction of the atria. 3 During which portion of the cardiac muscle contraction is it possible to induce an extrasystole? You correctly answered: during relaxation. Experiment Data https://media.pearsoncmg.com/bc/bc_0media_ap/physioex/10/ex6/act1/ 1/3

3/17/24, 4:.05 PM PhysioEx Exercise 6 Activity 1 Single Stimulus (Extrasystole) IFY Y Y S T A A T I AL A A A A Y A WY A WY .ll.lllll'llIl]l---ll-ll-l 0 1 2 3 4 5 6 7 8 9 10 Time (sec) Multiple Stimuli (Extrasystole) [ [ AT I T AT IV A VA Y [ A A V7 R VAN T A Fall":Ar. 0 W 3 0 1 2 3 4 3 6 7 8 9 10 I A T A A O T AV A AdTa VA Time (sec) Post-lab Quiz Results You scored 100% by answering 4 out of 4 questions correctly. 1 The amplitude of the ventricular systole did not change with the more frequent stimulation because You correctly answered: a new contraction could not begin until the relaxation phase. 2 Which of the following do you think contribute to the inability of cardiac muscle to be tetanized? You correctly answered: the long refractory period of the cardiac action potential. 3 Given the function of the heart, why is it important that cardiac muscle cannot reach tetanus? You correctly answered: The ventricles must contract and relax fully with each beat to pump blood. 4 An extrasystole corresponds to You correctly answered: an extra ventricular contraction. Review Sheet Results 1 Explain why the larger waves seen on the oscilloscope represent the ventricular contraction. Your answer: 2 Explain why the amplitude of the wave did not change when you increased the frequency of the stimulation. (Hint: relate your response to the refractory period of the cardiac action potential.) How well did the results compare with your prediction? Your answer: 3 Why is it only possible to induce an extrasystole during relaxation? Your answer: 4 Explain why wave summation and tetanus are not possible in cardiac muscle tissue. How well did the results compare with your prediction? https://media.pearsoncmg.com/bc/bc_Omedia_ap/physioex/10/ex6/act1/ 2/3

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