Cardiology 3: The Cardiac Cycle Flashcards
blood flow is determined by ____ difference across valves
pressure
blood flows from an area of ___ pressure to an area of ___ pressure
high; low
what is normal BP?
120/80
in 120/80 mmHg, what is 120? what 80?
120 is peak BP; 80 is diastolic BP
at end diastole, the pressure in the ventricles is what value?
almost zero
at end diastole, the pressure is ____ in the atria compared to ventricle
higher
during isovolumetric ventricular contraction, the AV valved are ___ and the aortic and pulmonary valves are __
closed; closed
isovolumetric ventricular contraction starts at the end of ___
diastole
during ventricular systole, does the ventricle or atria have higher pressure?
ventricle
during ventricular systole, is the pressure higher in the ventricle or the pulmonary/aorta?
pulmonary artery and aorta
during ventricular ejection, the AV valves are __ and the aortic/pulmonary valves are ___
closed; open
during ventricular ejection, is the pressure higher in the ventricle or the arteries?
ventricle
during isovolumetric ventricular relaxation, the AV valves are ___ and the pulmonary/aorta valves are ___
closed; closed
during ventricular filling, the AV valves are ___ and the pulmonary / aorta valves are __
open; closed
what is cardiac output?
volume of blood ejected from the heart per minute
cardiac output may be varied by changes in what 2 things?
- heart rate
2. stroke volume
cardiac output is measured as what equation?
stroke volume x heart beat
what is stroke volume?
amount of blood pushed out of the heart per contraction
heart rate is determined by
rate of SA diastolic depolarization (pacemakeer electricla activity)
stroke volume is determined by what 3 cardiac mechanical factors?
preload, afterload and contractility
heart rate is regulated by the ____ nervous system
autonomic
both divisions of the ANS influence SA node activity by altering rate of ____
diastolic depolarization
parasympathetic stimulation has ___ latency and ___ decay which allows ___ control of function
short; rapid; beat-by-beat
sympathetic stimulation is more ___ to act and decays ___
slow; gradually
resting heart rate is primarily determined by what branch of the ANS?
parasympathetic
which has stronger effect of heart rate, parasympathetic or sympathetic?
parasympathetic
what is preload?
force that stretches relaxed muscle ( determines ventricular filling)
what is afterload?
force against which muscle must contract (resistance to blood flow)
what is contractility?
intrinsic ability of muscle to generate force at a given preload and afterload
t/f afterload doesnt have an effect until the muscle is contracted
true
Can more heart muscle be recruited to increase the force of contraction? Why/Why not?
all cardiac muscle contracts with every heartbeat, so there is nothing else to recruit, it all working all the time
a change in force occurs by change in __
preload contractility
increased preload is increased by increased ___ to the heart, which causes tissue ___, resulting in more actin-myosin interactions
return of blood; stretch
with increased pre-load, actin-myosin interactions are increased by what 2 factors?
- increased sensitivity to ca
2. decreasing inter-filament spacing
does a stretched or shortened muscle create more force?
stretched
increasing preload increases cardiac output by increasing stroke volume in an effect known as the ____
frank-starling mechanism
sympathetic activity affects intracellular ___ dynamics and increases all of them
Ca
sympathetic activity increases the __ and ___ of force generation (as well as rate of relaxation)
magnitude and rate
t/f sympathetic activity also increases the rate of relaxation so heart is ready to regenerate force more quickly
true
parasympathetic activation act by what NT at what receptors and what isthe effect?
ach; muscarinic; inhibit release of NE from neighbouring sympathetic nerve enedings
