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atria systole in the cardiac cycle
atria contract, pressure increases in atria, blood flows through open AV valves into relaxed ventricles, end-diastolic volume of filled ventricle
ventricular systole in the cardiac cycle
ventricles contract, (simultaneous atrial diastole- atria relax) pressure increases in ventricles, AV valves close, isovolumetric contraction, semilunar valves open, ventricular ejection
pressure in ventricle increases but volume stays the same until pressure is greater than pressure in aorta or pulmonary trunk
pressure in ventricle decreases but volume stays the same until pressure is less than atrial pressure
artery between pulmonary trunk and aorta, shunts blood from pulmonary trunk to aorta.
stroke volume, heart rate, cardiac output, regulation of heart rate, autonomic nervous system regulation, chemical regulation, other factors
cardiac output (CO)
volume of blood ejected by each ventricle/minute (equal for right and left ventricles)
difference between maximum cardiac output and resting cardiac output, normally 4-5 times resting CO
stretch (fullness) of ventricle before contraction >EDV = >preload = stronger contraction, pericardial sac prevents overstretching heart muscle, preload is affected by filling time and venous return
positive inotropic agents
increase contractility (most increase Ca entering cardiac muscle cells) sympathetic NS, epinephrine, digitalis, Ca ions
negative inotropic agents
decrease contractility, parasympathetic NS, calcium-channel blockers, beta-blockers (block sympathetic response)
pressure in aorta/pulmonary trunk, resists ejection of blood from ventricles, high blood pressure and atherosclerosis decrease SV
increase heart rate
up to maximum heart rate (too high HR decreases filling time = decreases preload
emotions (fear, excitement, anxiety) sensory-proprioceptors: physical activity, chemoreceptors: oxygen, carbon dioxide levels, baroreceptors: blood pressure
output- sympathetic (norepinephrine)
cardiac accelerator nerves- bets receptors in SA and AV, nodes- increases depolarization rates
output- parasympathetic (acetylcholine)
vagus nerves- SA and AV nodes, decreases depolarization rates, predominate at rest
hormones, adrenal medulla (sympathetic) - epinephrine, norepinephrine, increases heart heart rate, thyroid hormone- increases heart heart rate
other factors affecting heart rate
body temperature: hyperthermia (faster HR), hypothermia (slower HR), fitness (decreases HR), electrolyte levels (Na and K decreases HR, Ca increases HR)
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