The attached table illustrates the distribution of the systemic cardiac output to the various organs at rest and during strenuous exercise. What physiological mechanisms produce the changes in blood distribution in each system depicted in the table? Consider the competing homeostatic demands strenuous exercise places on the body. Why might exercising on an extremely hot summer day result in fainting?
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Table 1. Distribution of systemic cardiac output at rest and during strenuous exercise.
Flow at rest (ml/min) Flow during strenuous exercise (ml/min)
Brain 650 (13%) 750 (4%)
Heart 215 (4%) 750 (4%)
Skeletal muscle 1030 (20%) 12,500 (73%)
Skin 430 (9%) 1900 (11%)
Kidneys 950 (20%) 600 (3%)
Abdominal organs 1200 (24%) 600 (3%)
Other 525 (10%) 400 (2%)
Total 5000 17,500
Distribution of cardiac output to each organ is regulated as follows:
at rest ? during strenuous exercise
Brain You'll note that flow remains the same to the brain in terms of volume. This is because the metabolic demands of the brain change very little, regardless of exercise status. Thus, the brain requires the same amount of cardiac output at all times. Cerebral blood flow is tightly ...
Cardiac output homeostasis and blood distributions are examined.