Biology, Eighth Edition (Raven)

Chapter 49: The Circulatory and Respiratory Systems

Chemoreceptor Reflex Control of Blood Pressure

Why would the chemical composition of the blood affect heart rate? Blood chemistry is determined, to a large extent, by the concentrations of gases in the blood. High carbon dioxide concentrations and low oxygen concentrations both indicate that gas exchange is occurring at a slower than ideal rate. The low rate of gas exchange could be due to rapid metabolism or to a low concentration of oxygen in the external environment. By monitoring blood chemistry the body is able to increase the heart rate and the rate of gas exchange to compensate. Similarly, if the oxygen concentration is high or the carbon dioxide concentration is low then the heart rate can slow down to conserve energy.

View the animation below, then complete the quiz to test your knowledge of the concept.



1.

Chemoreceptors in the carotid and aortic bodies detect all of the following except...
A)oxygen levels
B)blood pressure
C)pH
D)carbon dioxide
E)both A and D
2.

Chemoreceptors are also located in the...
A)medulla oblongata.
B)pons.
C)hypothalamus.
D)thalamus.
E)spinal cord.
3.

Which of the following will not increase the heart rate?
A)decreased blood oxygen
B)increased blood carbon dioxide
C)increased blood pressure
D)decreased blood pH
4.

Increased sympathetic stimulation causes increased heart rate and stroke volume.
A)True
B)False
5.

Chemoreceptors in the hypothalamus monitor blood carbon dioxide and pH.
A)True
B)False
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