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CARDIOVASCULAR
SYSTEM
CHAPTER 15
BLOOD PRESSURE
BLOOD PRESSURE

Definition
– Fluid pressure exerted on walls of vessels
– Usually arterial pressure
 Decreases as distance from heart decreases

Fluctuations between ventricular contractions
– Systolic number – top number
 Pressure as ventricles contract
 Arteries expand  pulse
– Diastolic – bottom number
 Resting pressure as ventricles relax
– Pulse pressure – difference between systolic and diastolic
pressures

Directly related to cardiac cycle
DIAGRAM
HOW TO TAKE – C.A. 15.5 (598)


Sphygomanometer
Attach cuff to upper left arm
– Brachial artery

Increase cuff pressure greater than arterial pressure
– Place stethoscope on antecubital
– No sound  no blood flow

Slowly decrease pressure
– 2-5 mmHg / sec for best results

Korotkoff’s Sound – thump
– When you first hear sound – Systolic
– When you stop hearing sound – diastolic

Normal values: 120/80
– Younger people – lower normal BP
– Hypertension – abnormally high BP
PRESSURE IN VESSELS
FACTORS AFFECTING PRESSURE

Heart Action
– Stroke Volume – amt. / heart beat
– Cardiac Output – amt. / minute
 Stroke volume X heart rate
– Increase action: increase BP

Blood Volume
– More Blood: higher BP

Blood Viscosity
– Peripheral Resistance
 Vasoconstriction and vasodilation
– Disease
 Atherosclerosis – fatty deposits (cholesterol)
 Arteriosclerosis – hardening of arteries
CONTROL AND PROBLEMS

Starling’s Law of Heartgreater the distention:
greater the force of
contraction

– Silent killer – heart
overgrowth
– Aneurysm
– Embolisms
– Stroke
– Keeps blood flowing

Baroreceptors in carotid
art. and aorta
– Cardiac center
– Parasympathetica and
sympathetic NS

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
Exercise, body temp,
emotions
Vasomotor reflexes
Chemical influences
– CO2, H+ ions, O2
Hypertension – chronic
high blood pressure

Kidney diseases
– Angiotensin II
– Alsosterone




High sodium
Obesity
Stress
Treatment:
– Lifestyle and medications
Blood Pressure and the Cardiac Cycle
Pressure Vs Distance