Homework

Chapter 20 Questions Josh Buchanan 1

16. Name the two valves that separate the right atrium from the right ventricle and the left atrium from the left ventricle. What are the functions of the papillary muscles and the chordae tendinea?

The tricuspid AV valve separates the right atrium from the right ventricle and the Mitral-Bicuspid AV valve separates the left atrium from the left ventricle. The papillary muscle contract when the ventricles contract and prevent the valves from opening into the atria by pulling on the chordae tendinea attached to the valve cusps.


22. What substances do cardiac muscle cells use as an energy source? Do cardiac muscle cells develop an oxygen debt?

Cardiac muscle cells use adenosine triphosphate as a source for energy. Cardiac muscle cells cannot and do not develop an oxygen debt.

30. What does and ECG measure? Name the waves produced by an ECG, and state what events occur during each wave.

An ECG measures the electrical activity occurring in the heart. An ECG records P waves, QRS complex, and a T wave. The P wave is a result of the depolarization of the atria. The QRS complex occurs as a result of the depolarization of the ventricles. The T wave occurs as a result of the repolarization of the ventricles.

32. List the five periods of the cardiac cycle, and state whether the AV and semilunar valves are open or closed during each period.

1. Systole: period of isovolumic contraction. Semilunar and AV valves are both closed.
2. Systole: period of ejection. Semilunar valves are opened, AV valves are closed.
3. Diastole: period of isovolumic relaxation. Semilunar and AV valves are closed.
4. Diastole: passive ventricular filling. Semilunar valves are closed, AV valves are opened.
5. Diastole: active ventricular filling. Semilunar valves are closed, AV valves are opened.

43. What effect do parasympathetic stimulation and sympathetic stimulation have on heart rate, force of contraction, and stroke volume?
Parasympathetic stimulations have an inhibitory influence on the heart, primarily by decreasing heart rate. There is little effect on stroke volume, it may even increase. Sympathetic stimulation increases both the heart rate and the force of muscular contraction. Stronger contractions can also increase stroke volume.