Multiple Choice
Valves of the heart open and close due to ________.
A) contraction of papillary muscles
B) timing sequences
C) electrical signals
D) pressure changes
E) None of the answers are correct.
Correct Answer:

Verified
Correct Answer:
Verified
Q136: Figure 21.1<br> <img src="https://d2lvgg3v3hfg70.cloudfront.net/TB4856/.jpg" alt="Figure 21.1
Q137: Cardiac pacemaker cells of the SA node
Q138: Figure 21.4<br> <img src="https://d2lvgg3v3hfg70.cloudfront.net/TB4856/.jpg" alt="Figure 21.4
Q139: The primary function of the pericardial fluid
Q140: The _ carries blood to and from
Q142: Figure 21.3<br> <img src="https://d2lvgg3v3hfg70.cloudfront.net/TB4856/.jpg" alt="Figure 21.3
Q143: Figure 21.4<br> <img src="https://d2lvgg3v3hfg70.cloudfront.net/TB4856/.jpg" alt="Figure 21.4
Q144: Figure 21.4<br> <img src="https://d2lvgg3v3hfg70.cloudfront.net/TB4856/.jpg" alt="Figure 21.4
Q145: Figure 21.3<br> <img src="https://d2lvgg3v3hfg70.cloudfront.net/TB4856/.jpg" alt="Figure 21.3
Q146: Figure 21.1<br> <img src="https://d2lvgg3v3hfg70.cloudfront.net/TB4856/.jpg" alt="Figure 21.1