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epicardium, myocardium, endocardium |
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thin-walled reservoir for systemic venous blood |
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propels blood into pulmonary circulation low pressure 1/3 thickness of left ventricle |
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receives oxygenated blood from lungs |
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high pressure thick muscles pressure exceeds right by five fold forces blood into aorta |
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cusps attached to thin strands of fibrous tissue called chordae tendinea |
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Where do chordae tendinea extend to? |
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semilunter valves (3 symmetrical cuplike cusps) |
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secured to fibrous ring above cusps of aortic vavle are three outpouchings of the aortic wall called the sinuses of Valsalva |
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opening to coronary arteries located within these outpouchings |
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ability to spontaneously generate impulses |
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regularity of impulse generation |
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Definition
ability to transmit impulses |
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ability to response to stimulation |
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sympathetic nervous system |
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Definition
increases both heart rate and force of cardiac contraction sympathetic receptors are beta receptors |
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electrical excitation of heart |
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-90 mV sodium outside cell and potassium inside negative cell inside and positive cell outside |
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+30 mV increased membrane permeability to sodium so inside becomes positive and outside becomes negative |
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Definition
small, abrupt change in ionic concentration and relative electrical change occurs due to influx of chloride ions which reduces positive influence a little |
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Term
mid diastole phase of cardiac cycle |
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Definition
slow ventricular filling or "diastasis" atrial and ventricular chambers are relaxed |
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Late diastole phase of cardiac cycle |
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Definition
depolarization spreads through atria causing atria to contract, forcing blood into ventricles |
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Early systole phase of cardiac cycle |
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Definition
depolarization spreads through ventricles causing AV valves to close which generated first heart sound semilunar valves remain closed |
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late systole phase of cardiac cycle |
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Definition
ventricular pressure exceeds pressures within vessels causing semilunar valves to open and ventricular ejection |
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early diastole phase of cardiac cycle |
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Definition
repolarization spreads through ventricle and chambers relax prsesure drops blow arterial pressures, causing semilunar valves to close which produces heart sound pressure continues to drop causing AV valves to open allowing filling of ventricles |
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Definition
represents atrial depolarization |
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time from onset of atrial activation to onset of ventricular activation 0.12 to 0.20 seconds |
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represents ventricular depolarization 0.06 - 0.10 seconds |
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represents time between end of spread of the impulse through the ventricles and repolarization of ventricles 0.12 seconds |
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represents ventricular repolarization |
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"electrical systole" of the ventricles 0.4 seconds |
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quantity of blood ejected by each ventricle per minute normally equals around 5 liters |
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Cardiac Output(CO)= cardiac rate X stroke volume |
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ventricles fill during relaxation to an end diastocilic volume of 100 ml of blood contraction typically forces about 2/3 of this volume into arterial blood vessels, leaving 30 ml in the ventricles at end of systole (end systolic volume or ESV) |
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What are the 3 factors that infleuence ESV or SV? |
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Definition
preload, contractility, and afterload |
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Term
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Definition
refers to stretch of myocardial muscle initiated by return of venous blood to the heart as increasing quanities of blood enter the atria, an associated rise in intra-atrial and intraventricular pressures should cause an increase in cardiac output |
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Definition
alterations in strength of caridac muscle contraction caused by factors other than preload stretch |
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What causes contractility to increase? |
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Definition
exposure to calcium, norepinephrine, or epinephrine and stiumalation by sympathetic nervous system |
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What causes contractility to decrease? |
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Definition
acidosis, hypocalcemia, hyperkalemia, and parasympathetic neural stimualtion |
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amount of force that must be gerenated during systole to eject blood into aterial vessels varies primarily as function of arterial blood pressure and ventricular radium explains why myocardial work must increase under certain conditions if stroke volume is to be maintained (if rising arterial blood pressure poses resistance to exit if blood from heart, the cardiac muscle will have to exer great effort to sustain output) |
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What are the three layers of the blood vessels? |
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Definition
tunic intima (innermost), tunica media (middle), and tunica externa or adventitia (outermost) |
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What are arterial walls composed of? |
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Definition
elastic connective tissue, fibrous connective tissue, and smooth muscle |
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have thick tunica media with more elastic fibers than smooth muscle ex: aorta and pulmonary trunk |
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contain more muscle fibers than elastic thus affected more by vasoconstriction/vasodilation |
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lumen diameteres of less than 0.5 mm and are composed almost entirely of smooth muscle |
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What do the capillary walls contain? |
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simple squamous epithelium---only tunica intima |
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force exerted on liquid (blood) per unit area expressed as dynes per square centimeter, mm Hg, or torr |
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opposition to force in blood most resistance provided by diameter and length of blood vessels resistance is inversely related to blood floow flow varies inversely to viscosity of fluid |
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neural control of total peripheral resistance |
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Definition
autonomic nervous system can regulate cardiac output and peripheral resistance |
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increase in volume a vessel can accommodate for a given increase in pressure depends on ratio of elastic fibers to muscle fibers |
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