PHIS 206 Lecture Notes - Lecture 13: Cardiac Output, Heart, Blood Pressure
2 May 2018
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Lecture 13: Regulation of Cardiac Output
Circulatory System/Vasculature
• Two Circulations
o Correspond with two hearts
o Systemic circulation → Supplied by Left Heart
o Pulmonary Circulation → Supplied by Right Heart
•
Distributions
• Cardiac Output
o The flow from the heart per minute is cardiac output
o In the systemic circulation, the cardiac output is divided between organs and
tissue beds in a parallel fashion (everyone receives fresh blood)
• Pumps 5 liters a minute
• Right and left heart pump 5 liters a minute
• Parallel arrangement → everybody gets the same fresh blood (no one gets used blood)
• Some of the blood that comes out of the digestive system goes to the liver (liver gets has
two blood supplies -- fresh and spent blood) → the blood from the digestive system is
high in nutrients
How to Make it Flow
• Pressure
o A change in pressure from point A to point B will drive the flow of blood between
A and B
o Remember, it’s not the amount of pressure, but the change in pressure
o Flow is proportional to the change in pressure (when the change in pressure
increases, the flow increases; when the change in pressure decreases, the flow
decreases)
• Change in pressure is proportional to change in flow
• Change in pressure is causing the change in flow
Resistance
• While flowing, friction between the blood and the inside wall of the vessel begins to slow
the blood down, reducing the flow
• This is the resistance of the vessel
• Friction between tube and whatever is flowing inside of the tube slows it down
• Same amount of blood in small tube touches more (more resistance to flow) of the tube
than same amount in a big tube (less resistance to flow)
• Easier to move fluid through big tube
Resistance and Radius
• Resistance to flow
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