Physio Ex Exercise 6 Activity 1 PDF

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2/13/2021

PhysioEx Exercise 6 Activity 1

PhysioEx Lab Report Exercise 6: Cardiovascular Physiology Activity 1: Investigating the Refractory Period of Cardiac Muscle Name: Kyleigh Hankton Date: 13 February 2021 Session ID: session-24359116-7d0b-2a6a-56a4-0d72dd771770

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 not change. 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 https://media.pearsoncmg.com/bc/bc_0media_ap/physioex/10/ex6/act1/

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2/13/2021

PhysioEx Exercise 6 Activity 1

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: 60 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

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. i https://media.pearsoncmg.com/bc/bc_0media_ap/physioex/10/ex6/act1/

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2/13/2021

PhysioEx Exercise 6 Activity 1

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: Ventricle contraction is stronger than atrial contraction. 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: Amplitude did not change because of the cardiac long refractory period, as predicted. 3 Why is it only possible to induce an extrasystole during relaxation? Your answer: The extrasystole can not occur until relaxation and so we could not achieve wave summation tetanus. 4 Explain why wave summation and tetanus are not possible in cardiac muscle tissue. How well did the results compare with your prediction? Your answer: Cardiac cells have longer twitches than any other muscle cells. As I correctly predicted, the cardiac muscle tissue showed neither wave summation nor tetanus.

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