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The Heart
Cardiac Output
15
Physiology
Undergraduate 2
09/20/2010

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Term
Ventricular Systole
Definition
starts when the AV valves close and the pressure within the ventricles begins to rise as the cardiac muscle fibers are depolarized and then contract
Term
ventricular diastole
Definition
starts with ventricular muscle repolarization, leading to a drop in ventricular pressure, and filling of the ventricle
Term
atrial systole
Definition
very brief; thus, ventricular filling is largely passive
Term
Cardiac output (co)=
Definition
(sv)(hr) stroke volume times heart rate
Term
Determinants of Stroke Volume (3)
Definition
preload end diastolic volume
afterload aortic blood pressure
contractility
Term
Afterload- Ventricles can not eject blood into the aorta or pulmonary artery until
Definition
the pressure in the ventricle exceeds the pressure in the vessel
Term
afterload- increase in pressure will
Definition
have a major impact on the work of the heart & on stroke volume
Term
stroke volume can not increase unless
Definition
rate of cardiac filling also increases
Term
preload goes _________ heart
afterload goes _____ heart
Definition
down; up
Term
active contractility
passive contractility
Definition
stimulation of sympathetic nerves in heart wall
result of changing the length of cardiac muscle fibers(frank starling mechanism)
Term
Frank Starling Mechanism refers to
Definition
increase in stroke volume and increase in preload
Term
epinephrine and norepinephrine lead to
Definition
increase rate of pacemaker activity and increased force of cardiac muscle contraction
Term
Action potentials invade the __ __________; _______ is released from sarcoplasmic reticulum
Definition
t tubules; calcium;
Term
The norepinephrine also increases the _______________ of the cardiac muscle fibers to _________
Definition
permeability; calcium
Term
In active contractility, the number of actin myosin crossbridge interactions _________ due to the permeability of calcium to cardiac muscle fibers
Definition
increases
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