The Cardiac Cycle and
Blood Pressure
Wednesday, March 20th
Cardiac Cycle
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One complete heartbeat is a full cardiac
cycle
Composed of two phases
o Systole
o Diastole
During (ventricular) systole the ventricles
contract
During (ventricular) diastole the ventricles
relax
Cardiac Cycle
Cardiac Cycle Animation
Ventricle
Diastole
Systole
AV Valve
Aortic and
Pulmonary Valve
Aorta
Heart Sounds
Lubb-Dupp
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Lubb - First heart sound. AV Valves close,
semilunar (aortic and pulmonary) valves
open. Beginning of systole.
Dupp - Second heart sound. Semilunar
valves close. Beginning of diastole.
Heart Sounds
Blood Pressure
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Remember!!!
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The arteries are very elastic!
We can take a pulse using an artery.
 What happens to someone's pulse if they lose a
lot of blood?
 Why?
Determined using a
sphygmomanometer
and a stethoscope OR
an electronic
sphygmomanometer
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Blood Pressure
Measurement of arterial pressure produced
during the cardiac cycle
o Measure systolic and diastolic pressure
 Which will have the higher reading? Why?
Normal blood pressure is below 120/80
120 is the systolic pressure
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Pressure caused by blood being pumped into the
aorta during systole
Highest amount of pressure on the arteries
80 is the diastolic pressure
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Pressure caused by ventricular relaxation during
diastole
Taking Blood Pressure
As you watch the video, answer these
questions:
1. How should you sit?
2. How should your arm be placed?
3. List 2 things you should not do while having
your blood pressure taken.
4. Where should the cuff be placed?
5. How is the systolic (top) measurement
determined?
6. How is the diastolic (bottom) measurement
determined?
How to Take Blood Pressure
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Blood Pressure Problems
Hypertension -- high blood pressure
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Causes
 too much blood
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arteries are too narrow or too stiff
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blood pressure tends to increase as we age
Hypotension -- extremely low blood pressure
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high salt intake causes high blood pressure
Causes
 some medications
 going from sitting to standing, especially when
dehydrated
Preeclampsia -- high blood pressure in late
pregnancy
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Causes unclear