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39 Cards in this Set
- Front
- Back
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what is flow through the heart
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body(vena cavae), RA, tricuspic(av) valve, RV, pa, lungs, pv, la, mitral(av valve, lv, av, body
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what do papillary muscles do
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limit movement of valves so they aren't pushed too far open --> ensure unidirectional flow
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what are cardiomyocytes
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single cells, smaller than skeletal muscle fibers; gap junctions allow AP to spread rapidly; rich in mitochondria
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what is the pathway of electrics in the heart
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SA --> internodal pathways, av node, bundle of his, purkinje fibers
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why can't there be tetanus
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long AP because of Ca channels that open after the closing of Na channels
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what is the sa node
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generates action potentials with voltage gated Ca channels; generates 100AP/minute
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what is the pacemaker potential
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depolarization due primarily to na, then threshhold and AP is generated due to Ca
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how many action potentials would the av node produce
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35-40
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how is heart rate affected by sympathetic
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NE released increases depolarization
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how is heart rate affected by parasympathetic
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ach released decreases depolarizations
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in an ekg, what is one heart beat
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1PQRST
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what is P
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atrial depolarization
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what is QRS
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ventricular depolarization
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flat area?
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no change in charge
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T
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ventricular repolarization
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what is not seen on a ekg
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atrial repolarization because signal gets lost in ventricular depolarization
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what is normal heart rate
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~72bpm
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how long does each cycle last?
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~800msec
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what are the two phases in the heart cycle
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diastole and systole
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what is diastole
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cardiac muscle relaxes, heart fills, 500msec
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what is systole
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cardiac muscle contracts; heart empties; 300msec
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what is the first step in the heart cycle
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atrial and ventricular diastole; atria fill with bl. from veins; av valves open because of increased pressure in atria; semilunar valves closed; passive flow
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what is the second step?
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atrial systole; completion of ventricular filling (20% bl. is forced), follows depolarization of SA node; av valves still open
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what is EDV?
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end diastolic volume ~135mL
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What is the third step
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isovolumic ventricular contraction; pushes AV valves closed (lub sound); both valves closed;
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what is the fourth step?
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ventricular ejection; semilunar valves open
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what is ESV
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end systolic volume ~65mL
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what is the last step
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ventricular relaxation; Pventricles<Parteries; semilunar valves close (louder DUP sound); isovolumix
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what is a heart murmur?
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bl. through constricted passages
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what side of the heart creates a larger pressure
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left side
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what is stroke volume?
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amount of blood pumped by one ventricle during contraction; SV=EDV-ESV = 135-65=70mL
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what is cardiac output
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amount of blood pumped by heart in a given amount of time; CO=HRxSV = 5L/min
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how is heart rate regulated?
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SA node; PNS slows HR, SNS speeds HR
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how does PNS slow HR
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ACh on muscarinic receptors slows rate of depolarization through SA node
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how does SNS quicken HR
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NE on beta 1 receptors increases rate of depolarization through SA node
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how is SV regulated
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increasing EDV or decreasing ESV; related to force generated during contraction;
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what is starling's law
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SV increases in proportion to EDV
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what are ways venous return can be increased
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skeletal muscle pumping, respiratory pumping, venoconstriction by SNS(more bl. in heart)
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what is the ejection fraction
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proportion of amt. of bl. in the ventricle pumped out SV/EDV
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