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Unformatted text preview: Cardiovascular Needs I • Heat disease is the # 1 killer in US Functions *Heart pumps blood to every cell in the body as well to itself • Coronary artery pumps blood to the heart • Left main CA separates to left anterior descending and left circumflex artery • RCA supplies posterior and inferior part of the heart • Coronary arteries are perfused during diastole (relaxation) • If the heart rate speeds up, diastole is shorter, less blood gets through, increasing the chance of myocardial ischemia • Widow maker à Left anterior descending artery block or left main artery blockage (almost all the heart is blocked from receiving oxygen) à • The heart has a large metabolic requirement. The heart extracts 70-80% of the oxygen delivered to it. The other organs take up about 25% *Cardiac conduction system stimulates the mechanical part of the heart *Arteries carry oxygenated blood & nutrients to the tissues (away from the heart) *Veins carry deoxygenated blood back to the heart (veins) to be oxygenated *Removes waste products *Carries hormones and electrolytes around • In the right side of the heart, the pressure generated during ventricular systole (15-25 mm Hg) exceeds the pulmonary artery diastolic pressure (8-15 mm Hg) and blood is ejected into the pulmonary circulation. During diastole, venous blood flows into the atrium because pressure in the superior and inferior vena cava (8-10 m Hg) is higher than that in the atrium. Blood flows through the open tricuspid valve and into the right ventricle until the 2 right chamber pressures equalize (0-8 mm Hg). Pressure is higher on the left side of the heart • In the left side of the heart, as pressure mounts in the left ventricle during systole (110-130), resting aortic pressure (80 mm Hg) is exceeded and blood is ejected into the aorta. During left ventricle ejection, the resultant aortic pressure (110- 130) forces blood through the arteries. During diastole, oxygenated blood returning from pulmonary circulation flows into the atrium, where pressure remains low. At the end of diastole, pressure in the atrium and ventricle equilibrates (4-12 mm Hg) Blood Vessels *Arteries- carry blood away from the heart *Arterioles *Capillaries *Venules- *Veins- carry blood to the heart • Cardiac Output à amount of blood pumped by each ventricle per minute o Cardiac output in a resting adult is about 5 L per minute • Stroke volume à amount of blood ejected by each ventricle per heartbeat. The resting stroke volume is about 70 mL and the resting heart rate is about 60-80 1 BPM * Stroke volume x HR = cardiac output * Control of heart rate Reflex controls by the ANS *Parasympathetic- slows down *Sympathetic- increases Reflex controls by the CNS • Baroreceptors à specialized nerve cells located in the aortic arch and in right and left internal carotid arteries; sensitive to changes in BP....
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This note was uploaded on 05/04/2008 for the course NURS 130 taught by Professor Dupuy during the Spring '08 term at Lady of the Lake.
- Spring '08