LabQuest
Heart Rate, Blood Pressure,
and Exercise
11
DATA ANALYSIS KEY
1. Describe the trends that occurred in the systolic pressure, diastolic pressure, mean arterial
pressure and pulse with exercise. Assume that the stroke volume increased from 75 mL/beat
to 100 mL/beat. Use this information and the change in pulse with exercise to calculate the
change in cardiac output (stroke volume × heart rate) that occurred per minute.
Use your data to describe trends.
Resting cardiac output = (75mL/beat)(your baseline heartrate)
Cardiac output after exercise = (100mL/beat)(your exercise heartrate)
Difference=the effect of exercise
2. Pulse pressure is the difference between systolic pressure (peak pressure during active
contraction of the ventricles) and diastolic pressure (the pressure that is maintained even
while the left ventricle is relaxing). Describe the change in pulse pressure seen with exercise.
Which component of the blood pressure is most responsible for this change?
Increase in pulse pressure because of a rise in systolic, due to an increase in cardiac output due to
exercise.
3. A change in pulse pressure can be seen in a variety of medical conditions. What would you
expect to happen to the pulse pressure in the following examples?
(a) In atherosclerosis there is a hardening of the arterial walls.
Pulse pressure depends on distensibility of arterial walls, as well as cardiac output. In
atherosclerosis, there is a hardening of arterial walls making them less distensible. This causes a
higher systolic pressure and therefore a higher pulse pressure.
(b) A damaged aortic valve does not seal properly and allows blood to flow back into the
ventricle during diastole.
Diastolic pressure is maintained in part by a closure of the aortic valve. When this valve fails to
close completely, there is a backflow of blood into the left ventricle, reducing the
diastolic pressure. This means blood pressure would drop—the system is no longer
closed.
However pulse pressure may actually increase because of an accompanying increase in blood
volume pumped with each contraction of the left ventricle (blood from the left atrium
plus regurgitant blood from the aorta) which would increase systolic pressure.
Human Physiology with Vernier
11 - 1
LabQuest 11
4. Normal resting heart rates range from 55−100 beats per minute. What was your/the subject’s
resting heart rate? How much did your/the subject’s heart rate increase above resting rate
with exercise? What percent increase was this?
Answers vary: take into account factors such as weight, regular exercise, health, medications, etc.
that all play a part in determining the heart rate.
5. How does your/the subject’s maximum heart rate compare with other students in your
group/class? Is this what you expected?
Answers vary: take into account factors such as weight, regular exercise, health, medications, etc.
that all play a part in determining the heart rate.
We did not collect class data—use your group.
6. Recovery time has been shown to correlate with degree of physical fitness. How does
your/the subject’s recovery rate compare to that of your classmates? Is this what you
expected?
Answers vary: take into account factors such as weight, regular exercise, health, medications, etc.
that all play a part in determining the heart rate.
7. Congestive heart failure is a condition in which the strength of contraction with each beat
may be significantly reduced. For example, the ventricle may pump only half the usual
volume of blood with each beat. Would you expect a person with congestive heart failure to
have a faster or slower heart rate at rest? With exercise?
A person with congestive heart failure will tend to have a more rapid heart rate at rest and with
exercise. If less blood is pumped during each heart beat, the heart will attempt to compensate
by beating more rapidly.
8. Medications are available which can slow the heart or speed it up. If a patient complains of
feeling poorly and has a heart rate of 120 beats per minute, should you administer a medicine
to slow the rate?
No, the heart may beat rapidly to compensate for other problems, such as blood loss and low
blood pressure. In this case, slowing the heart with medication may lead to a precipitous and
fatal fall in blood pressure. One should not attempt to manipulate the heart rate before
ascertaining the underlying cause of the abnormality.
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Human Physiology with Vernier