cardiovascular - EXERCISE 6 CARDIOVASCULAR PHYSIOLOGY...

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1 EXERCISE 6: CARDIOVASCULAR PHYSIOLOGY ACTIVITY 1: Investigating the Refractory Period of Cardiac Muscle Answers 1. Which of the following types of muscle tissue can depolarize spontaneously in the absence of any external stimulation: a. Skeletal muscle b. Smooth muscle c. Cardiac muscle d. All of the above C- Cardiac Muscle 1. Look at Figure 6.1, the cardiac action potential. The period of time between the beginning of the cardiac action potential and the approximate middle of phase 3 is the __________________ refractory period of cardiac muscle. Absolute refractory period of cardiac muscle 1. In this simulation, when you delivered several single stimuli very rapidly, you saw a double peak. The second peak is called an ______________. Extrasystole 1. True or False: In order for the heart to function the most effectively in pumping blood, the ventricles must contract and then relax fully with each beat. TRUE 1. Explain why the larger waves seen on the oscilloscope represent ventricular contractions. The ventricles are larger chambers therefore, when they contract they generate more force thus producing a larger wave. 1. Explain why the amplitude of the wave did not change when you increased the frequency of the stimulation. The amplitude did not change because of the long absolute refractory period of cardiac muscle tissue which insures that the extrasystole doesn’t occur during contraction. 1. Why is it only possible to induce an extra systole during relaxation. (HINT: Relate your response to the refractory period of the cardiac action potential.) The stimulus applied during relaxation should cause an extra systole because it was applied when the cells were re- polarizing. 1. Explain why wave summation and tetanus are not possible in cardiac muscle tissue. Wave summation and tetanus are not possible in cardiac muscle because it has a relatively long absolute refractory period, 200-250 milliseconds which are almost as long as the contraction of cardiac muscle. Cardiac muscle does not react to any stimulus before the middle of phase 3 and will not respond to a normal cardiac stimulus before phase 4. ACTIVITY 2:
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This note was uploaded on 03/16/2012 for the course ADVANCED P 201 taught by Professor Chamberlain during the Spring '12 term at Ivy Tech Community College.

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cardiovascular - EXERCISE 6 CARDIOVASCULAR PHYSIOLOGY...

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