Lab Exercise 6 Activity 1 Cardiovascular Physiology

Lab Report Exercise 6: Cardiovascular Physiology 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: wave summation. 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: 59 beats/min. 2 Which of the following statements about the contractile activity is true? Your answer: The larger waves represent the contraction of the atria. Correct answer: 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? Your answer: midway through contraction. Correct answer: during relaxation. Experiment Data Post-lab Quiz Results You scored 25% by answering 1 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? Your answer: the autorhythmicity of the heart. Correct answer: 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? Your answer: The heart might stop. Correct answer: The ventricles must contract and relax fully with each beat to pump blood. 4 An extrasystole corresponds to Your answer: an extra atrial contraction. Correct answer: an extra ventricular contraction. Review Sheet Results 1 Explain why the larger waves seen on the oscilloscope represent the ventricular contraction. Your answer: larger waves represent ventricular contraction because the ventricles are stronger than the atria and pump with more force. the atria only have to pump blood a short distance into the ventricles, while the ventricles have to pump blood all throughout the body. 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: I predicted that the amplitude would increase, but really the amplitude did not change with frequency because the heart has a long stimulation refractory period. this prevents wave summation because if the heart did not have this refractory period, then it could become tetanic and cramp up. 3 Why is it only possible to induce an extrasystole during relaxation? Your answer: the cardiac muscle is only able to depolarize after it repolarizes because of the long refractory period, so the extrasystole is not able yo occur until the relaxation period. 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: i predicted that wave summation would occur after delivering multiple stimuli because of previous experiments. neither wave summation or tetanus are possible in cardiac muscle tissue because cardiac cells have longer action potentials and a very long refractory period compared to other cells. this helps prevent the heart from cramping or seizing, because of receiving too much stimulus.