Flashcards in CARDIAC CYCLE Deck (72)
what does the p wave of ECG represent?
depolarisation of SAN
this is not contraction of atrium
what does the QRS complex of ECG represent?
depolarisation of the ventricle
what is isovolumic contraction?
there is the same volume of blood as both valves are closed, but the pressure increases as the ventricles contract
what does the T wave of ECG represent?
repolarisation of the ventricle
what is isovolumic relaxation?
both valves close
the volume stays the same but pressure decreases as the ventricles relax
what is diastasis?
it is a period where there is equal pressure between atria and ventricles
what are the stages of left ventricular contraction?
what are the stages of left ventricular relaxation?
start of relaxation and reduced ejection
rapid filling and left ventricle suction
slow LV filling (diastasis)
what happens in ventricular contraction?
opening of L calcium tubule
the Ca2+ arrive at contractile proteins
LV pressure rises above LA pressure
the mitral valve closes - first heart sound
LV pressure rises (isovolumic contraction)
aortic valve opens and ejection begins
what happens in ventricular relaxation?
LV pressure peaks and then decreases due to ejection
cytosolic Ca2+ is taken up in sarcoplasmic reticulum
reduced ejection phase
LV pressure < aortic pressure so aortic valve closes (second heart sound)
isovolumic relaxation and mitral valve opens
what is the first heart sound?
mitral valve closing (M1)
what is the second heart sound?
the aortic valve closing (A2)
what happens during ventricular filling?
LV pressure < atrial pressure so the MV opens and rapid filling starts
ventricular suction also contributes to filling
filling temporarily stops (diastasis)
filling is renewed when atrial contraction (atrial booster) raises LA pressure
when is cardiologic systole?
it is between the 1st and 2nd heart sounds
closure of mitral valve and closure of aortic valve
when is physiologic systole?
both isovolumic contraction and ejection
when is physiologic diastole?
diastole starts before A2 heart sound (aortic valve closure)
then isovolumic relaxation and filling
when is cardiologic diastole?
it is between heart sounds A2 and M1
aortic valve closure and mitral valve closure
when does preload occur?
it is the load before ventricular contraction
when does afterload occur?
the load after the ventricle starts to contract
what happens when the mitral valve leaks?
the ventricle needs to raise pressure in order to overcome resistance
therefore the ventricular wall thickens - hypertrophy
what is starlings law?
the larger the volume of the heart, the greater the energy of it's contraction and the amount of chemical change at each contraction
it is a positive ionotropic effect
what is the force-length interaction?
a decrease in length of sarcomere results in a lower maximal force produced
the cardiac sarcomere at 80% of it's optimal length only has 10% of it's maximal force
what is contractility?
it is the ability of the heart to increase its contraction velocity to achieve higher pressure independent of load
what is elasticity?
it is the ability of the heart to recover normal shape after systolic stress
what is compliance?
it is the relationship between the change in stress and the resultant strain on the heart
what is the equation for compliance?
compliance = dP / dV
what is diastolic distensibility?
it is the pressure required to fill the ventricle to the same diastolic pressure
what are pressure volume loops?
it reflects contractility in the end-systolic pressure volume relationship
while compliance is reflected in end diastolic pressure volume relationship
what are the phases of the cardiac cycle?
isovolumic ventricular contraction
rapid ventricular ejection
reduced ventricular ejection
isovolumic ventricular relaxation