cardiac cycle Flashcards
what valves close and what valves open in atrial systole
- aortic and pulmonary valves close
- mitral and tricuspid valves open
what occurs during atrial systole
- contraction of the atria
- pressure within atria increases
- pressure gradient across the AV valves is generated
- contraction “tops off” filling
atrial contraction accounts for what percentrage of ventricular filling?
atrial contraction accounts for 10% of ventricular filling at rest
- most of the filling occurs before atrial contraction (during rapid and reduced filling)
what is the end-diastolic volume
when the volume of blood in the left ventricle is maximal
what occurs during isovolumetric contraction
all valves are closed
- initiated by QRS complex
- rise in vetricular pressure caused AV valves to close
- pressure rises without a change in volume
what valves close in isovolumetric contraction
AV valves
what happens to ventricular pressure during isovolumetric contraction
depolarization leads to rapid increase in LV pressure
ventricular ejection consists of what two phases
- rapid phase
- reduced phase
what valves are open and closed during rapid ejection
- semilunar valves (aortic and pulmonary valves) open
- AV valves remain closed
what occurs during rapid ejection
- when intraventricular pressures exceeds pressures within the great vessels, valves open and blood is ejected
- during this phase, maximal outflow velocity of blood is reached
- most of the volume of blood is ejected
- dramatic decrease in ventricular volume
when is maximal left ventricular systolic (and RV systolic) pressure achieved
rapid ejection
what is occuring in the atria as rapid ejection occurs
atrial filling begins, causing atrial pressure to rise
end of the rapid ejection phase coincides with what EKG property
with the end of the ST segment
what process occurs during reduced ejection
ventricles begin to repolarize, marked by the T wave
what valves are opened and closed during reduced ejection
- semilunar valves are open
- AV valves remain closed
what happens to ventricular pressure during reduced ejection
ventricular pressure falls because the ventricles are no longer contracting
*volume of blood in ventricles approaches the minumum
what is isovolumetric relaxation
- ventricles are fully repolarized
- All valves are closed
what causes the aortic and pulmonic valves to close during isovolumetric relaxation
left ventricular pressure declines dramatically, below that of vessel pressure, which causes the valves to close
what is the end-systolic volume
volume of blood in a ventricle at the end of contraction, or systole, and the beginning of filling, or diastole.
- ESV is the lowest volume of blood in the ventricle at any point in the cardiac cycle.
what occurs during rapid ventricular filling
- ventricular pressures fall below atrial pressures
- AV valves open and LV filling begins
what vavles are opened and closed during rapid ventricular filling
- AV valves are open
- SL valves are closed
what is the pressure in the left ventricle during rapid ventricular filling
LV pressure is low because the ventricle is relaxed
what is the reduced ventricular filling stage (diastasis)
final portion of passive ventricular filling
what is the longest phase of the cardiac cycle
reduced ventricular filling
during reduced ventricular filling, as ventricles continue to fill with blood, what happens to the pressure gradient across the AV valves
pressure gradient across the AV valves declines because the pressure in the ventricles begins to rise
what is the stroke volume
volume of blood ejected on one ventricular contraction
- difference between the volume of blood in the ventricle at end of atrial systole (EDV) and following reduced ejection (ESV)
how does stroke volume relate to end diastolic volume and end systolic volume
SV = EDV - ESV
what information does ejection fraction give us
effectiveness of ventricles in ejecting blood
what is ejection fraction? give equation
fraction of EDV that is ejected in one Stroke volume
EF = SV/EDV x 100%
what is cardiac output?
total volume of blood ejected per unit time
how does cardiac output relate to heart rate and stroke volume
CO = HR x SV
what is a stenotic valve
- stiff narrow valve
- does not open completely
- turbulence is created when blood must be forced through
what is an insufficient (regurgitation) valve
- valve can not close completely
- blood flows backward and collides with incoming blood
in aortic stenosis, what happens to left ventricular pressure? what happens to aortic pressure?
- left ventricular pressure is much greater than aortic pressure during ejection
- aortic pressure rise is slightly reduced
mitral valve stenosis leads to what pressure changes in left atria and left ventricle during filling
- resistance causes blood to back up reducing LV filling
- left atrial pressure is greater than left ventricular pressure during filling
*atrium must contract more, increasing left atrial pressure
what is aortic regurgitation
leaflets do not provide seal; blood regurgitates back into the LV
what happens to left ventricular volume in aortic regurgitation
increase in volume and pressure in LV chamber
how does the left ventricle try to compensate for aortic regurgitation
increasing Stroke volume
in aortic regurgitation, the increase in LVP causes what to atrial pressure
causes an increase in atrial pressure
what is mitral regurgitation
blood regurgitates from LV into left atrium during systole
what happens to left atrial pressure in mitral regurgitation
increases
* causes enlargement of the atrial chamber
what happens to left ventricular stroke volume during mitral regurgitation
decreases
