Cardiac Cycle Flashcards
(40 cards)
When the heart walls thicken during contraction, what does that mean? (not pathological)
thicken bc heart shortening and sarcomeres closer together, chambers getting smaller and forcing blood out through aorta
Why are recordings of venous pulse usually on the right side?
venous pulse is the acv wave .. recorded on R side bc catheter goes in groin, IV, and then to side of R atrium.
R atrial pressure = venous pressure. (no valve between R atria and IVC)
no valve, also low pressure side of body..the venous side of body) don’t put catheters in arterial system..high pressure system could break off clot,
What happens right before the p wave?
sinus node is activated right before the p wave, pressure is falling in arterial system from previous cycle, still in diastole from previous cycle.
so sinus node fires, conducts through atria muscle, and thats the p wave.
What is diastasis?
its the second part of filling. (reduced part)
Discuss atrial contraction.
impulse spreads across atria, when atria contracts it pumps a little blood through mitral valve into ventricle (that’s atrial systole which occurs during ventricle diastole) …atria only contribute about 5 percent or less under resting conditions to L ventricle - does become more important under exercise.
when vigorously exercising, atrial contribution is more significant to L ventricular filling - more like 10 percent
Why might someone not experience any symptoms of a fib under resting conditions? When might you experience symptoms?
no symptoms bc atria don’t contribute significantly to resting filling. under resting conditions affect Cardiac output. but exercise conditions it does. by reducing filling of L ventricle, you’re reducing preload, which is one of things in L-tension rel, that det. strength of contraction of L ventricle and thus SV. so walking quickly in airport or climb stairs- these people will get tired bc their cardiac output compromised a little bit.
What are the 3 phases of diastole?
rapid filling phase, slow filling phase, atrial systole/atrial kick.
Discuss the a wave in the venous pulse graph.
When R atria contracts it does generate an increase in pressure. (a wave)
What physical indication might you see when examining a patient in heart failure?
venous pulse recording is same venous pulse you look at in patients on neck (the jugular feeds right into SVC)…imp. in heart failure… bulging venous pulse in neck bc heart not able to empty.
Describe the impulse pathway.
impulse has already entered the AV node by the time get to p wave. impulse is sitting in AV node transferred from atria to ventricle.. slow conduction. now impulse enters His-P system. coming right into ventricle, activated QRS,
What is the first heart sound? What does it result from?
closure of mitral valve (closes as a result of passive pressure gradients, atria has just emptied blood into ventricle so pressure in atria is v low and in ventricle its high and that pressure gradients between the atrial and ventricular chambers closes the valve
not due to contraction of ventricle or activation of ventricle electrically. valve not electrically excitable- its a piece of connective tissue. doesn’t carry electrical impulses. just flappy valve. thin. easily open and close in response to pressure gradients. they’re completely passive. activation of chords tendenae/papillary muscle holding onto it preventing it from prolapsing in wrong direction when pressure is developed in ventricle
What causes the c wave in the venous pulse graph?
AP conduction around heart- QRS, that activates all cells within 100 ms. and those cells bring up pressure quite dramatically. at same time, this increase in pressure, see c wave. turns increase in pressure in ventricle is causing the mitral valve to bulge back - doesn’t open but pressure generated during isovolumic contraction is pretty high and it pushes the valve back and sends a pressure wave back into atria and into venous system.
Describe the isovolumic contraction phase.
isovolumic contraction - volume of ventricle is iso, not changing. mitral valve is closed and aortic valve is closed and ventricle is electrically activated to try to compress imcompressable fluid, so pressure goes up v high, requires ATP- a lot of it. this uses more energy than actual ejection of blood. isometric phase v energy consuming. increase in pressure occurs and is as close as heart gets to isometric contraction. shape of heart does change and some cells are stretching sarcomeres and others contraction but if you measure all, no change over time. shape may change but no change in volume. heart has to generate enough tension to overcome pressure on other side of valve, thats afterload, load on muscle after contraction starts
When does the aortic valve open?
as pressure increases and after load decreasing from previous cycle, will exceed it and open aortic valve at that point. explosive opening of aortic valve and blood ejected.
What are the two phases following isovolumic contraction?
after aortic valve opens bc of pressure in ventricle exceeding arterial pressure… rapid ejection- most volume is lost, slow ejection -
What is happening during ventricular systole in the atria?
blood returning to atria from venous return …blood back from SVC and IVC filling atrial chamber and that pressure goes up as result of filling of atria on both sides of heart. thats atrial diastole which is occurring during ventricular systole. cant have systole in both chambers at same time.
Why does ejection slow down?
one reason is that heart increasing pressure downstream from ventricle (arterial pressure) increasing its own afterload.
What happens to the amount of shortening of ventricular muscle as afterload increases?
it decreases. after load is high, so muscle has already shortened, at shorter muscle length and increased after load can generate less force. highest velocity of shortening is initial and later on is reduced (due to increase in after load and reduction in length of muscle) this phase is isotonic like contraction, but not pure isotonic. isotonic-like bc muscle shortening..isotonic contraction that has larger and larger after load in heart. bc it creates its own afterload. if arterial pressure at this point higher than ventricular pressure, how does blood move forward? bc of inertia, velocity of blood flow has energy to it, not strictly to pressure gradient, really energy gradient, part of energy is inertia, movement (kinetic and potential =pressure) so energy gradient is still forward.
What is happening during the t wave?
repolarization of the ventricle. Ca taken back into SR. pressure in ventricle is falling, pressure in arterial system falling as well, has ejected blood, ejection fraction of ventricle is about 60 percent in efficient and healthy heart.
Discuss the fraction of blood ejected with one stroke.
should have fraction of blood ejected with one stroke about 60 percent. leaving behind about 40 percent=blood left behind is end systolic volume. diff between end diastolic volume and end systolic volume= diff between when heart filled with blood and what’s left in heart=what was ejected. so that’s stroke volume.
As heart relaxes, after reduced ejection, what happens?
v low pressure in ventricle but pressure in arterial system quite high. in next phase what separates them? closure of aortic valve. as pressure in ventricle drops, at that moment pressure in ventricle lower than pressure in arterial system and that passively closes the aortic valve and causes the second heart sound. 2nd heart sound, closure of aortic and pulmonary valves, due to pressure has fallen below pressure in arterial system and that passively closes aortic valve. this decline in pressure is isovolumic relaxation
What is happening in isovolumic relaxation?
(no change in volume bc both valves closed) pressure is falling, both valves closed, so pressure in the ventricle is falling and pressure in arterial system not falling bc aortic valve closed.
What causes the notch in the pressure graph after the aortic valve closes?
aortic valve snaps closed then what happens to cause increase in arterial pressure? it bounces up… the aorta is most elastic tissue in arterial system, so what happens in normal heart is that blood ejected into arterial system (large volume) compliant arterial system, elastin in arterial wall allows arterial wall to distend bc its compliant. vessel extends, aortic valve closes and recoils, like rubber band, so that recoil is like secondary pump, blows up arterial pressure.
What would happen if the aortic valve did not recoil back after it closed?
if you didn’t have that… aortic valve closes, now diastolic pressure drops. not better bc now heart has to bring pressure from lower value all way back to 120, more work of heart. so low compliance of aorta- its independent risk factor for congestive heart failure. its an after load on heart…more difficult for heart to pump against fibrotic/low compliant aorta. important.
