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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 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