At rest, a person has a stroke volume of 70 mL and a heart rate of 72 beats a minute…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
At rest, a person has a stroke volume of mL and a heart rate of beats a minute. In hard exercise, the stroke volume is mL and the heart rate is beats a minute.
- What is the cardiac output at rest, in litres a minute?
- What is the cardiac output in exercise?
- How much more blood does the heart pump each minute in exercise?
Need a reminder? The key ideaShow
The cardiac cycle lasts about s: atrial systole s, ventricular systole s, joint diastole s. The valves between the atria and the ventricles are shut in the ventricular systole, and the semilunar valves are open only then. Cardiac output equals stroke volume times heart rate: in a minute.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. At rest: mL and a minute. In exercise: mL and a minute.
Plan. Cardiac output is the stroke volume times the heart rate.
Step 1. At rest. mL, which is L.
Step 2. In exercise. mL, which is L.
Step 3. The difference. L.
Answer: L; L; L.
Check. The output in exercise is about times the output at rest. Both the rate and the stroke volume have gone up.
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