1. Review textbook sections on the cardiac cycle and heart sounds.
2. Complete Part A of Laboratory Report 42.
3. Listen to your own heart sounds. To do this, follow these steps:
a. Obtain a stethoscope, and clean its earpieces and the diaphragm by using cotton moistened with alcohol.
b. Fit the earpieces into your ear canals so that the angles are positioned in the forward direction.
c. Firmly place the diaphragm (or bell) of the stethoscope on the chest over the apex of the heart (fig. 42.1) and listen to the sounds. This is a good location to hear the first sound (lubb) of a cardiac cycle when the A-V valves close.
d. Move the diaphragm to the second intercostal space, just to the left of the sternum, and listen to the sounds from this region. You should be able to hear the second sound (dupp) of the cardiac cycle clearly when the semilunar valves close.
4. Inhale slowly and deeply, and exhale slowly while you listen to the heart sounds from each of the locations as before. Note any changes that have occurred in the sounds.
5. Exercise vigorously outside the laboratory for a few minutes so that other students listening to heart sounds will not be disturbed. After the exercise period, listen to the heart sounds and note any changes that have occurred in them.
6. Complete Part B of the laboratory report.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.