NAME & section #:
PRELAB EXERCISE 4 (2002-2003)
CARDIOVASCULAR RESPONSES TO
CHANGES IN POSTURE AND TO EXERCISE
(Seeley 692-697, 740-746, 748-758)
Heart rate, stroke volume and peripheral resistance are regulated in order to maintain a
stable internal environment throughout daily life (homeostasis).
Arterial blood pressure (BP) is determined by cardiac output (CO) and peripheral resistance (PR):
BP = CO x PR.
Cardiac output is determined by heart rate (HR) and stroke volume (SV):
CO = HR x SV.
Arterial blood pressure then, can be defined as a function of the heart rate, stroke volume and
peripheral resistance:
BP = HR x SV x PR.
1.Define the following (Seeley 692-693,740-741, 753):
Blood Pressure (BP):
Stroke Volume (SV):
Heart Rate (HR):
Cardiac Output (CO):
Peripheral Resistance (PR):
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Various stimuli (eg. emotions, temperature, O2 levels, change in blood pressure, in blood volume,
in venous return to the heart, or in metabolite levels in skeletal muscles) will affect heart rate,
stroke volume and vascular resistance by their direct action on the heart or blood vessels (=
autoregulation, also called intrinsic regulation) or through the mediation of neural or humoral
efferent pathways (extrinsic regulation).
Briefly explain how the following regulate HR and SV (Seeley p. 693-697):
Parasympathetic control:
Sympathetic control:
Hormonal control:
2. Define the following (p. 694):
Venous Return (VR):
Preload:
Afterload:
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Explain the Frank Starling law of the heart. Using this law, explain how an increase in venous
return will result in an increase in SV.
3. Consider the following two equations for mean arterial pressure MAP = HR X SV X PR and
MAP = CO X PR to explain how the following situations would affect MAP:
Hemorrhage (decrease in blood volume):
Increase in blood flow to skeletal muscle during exercise (p. 694 and 754):
4. What are baroreceptors? Where are they located? Briefly explain the baroreceptor reflex.
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5. What stresses are imposed on the cardiovascular system when one stands up to get out of
bed? Why do you sometimes feel dizzy upon standing very quickly?
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