Flashcards in Lecture 11: Events of The Cardiac Cycle (Hayward) Deck (27):
For ECGs-Lead III involves putting your +/- electrodes on:
An increase in extracellular Na+ --> intracellular Ca conc.?
the repeating cycle of contraction (systole) and relaxation (diastole) which pumps blood through the circulatory system unidirectionally
Which valves are open/closed during diastole?
AV valves open, semilunar valves closed
systole is initiated by:
SA node discharge
duration of volume injection phase of systole is driven by duration of
AP (volume injection will occur when AP is in plateaue phase and will decrease once repolarization occurs)
when do ventricles fill?
2 phases of systole
isovolumic, volume injection
isovolumic phase of systole
ventricles begin to contract, pressure in ventricles is greater than P in atria, but lower than P out in vessels
volume injection phase of systole
valves open because pressure in ventricles becomes greater than P in outside vessels
AV valves open during:
diastole and atrial contraction
5 main phases of cardiac cycle
1) ventricular filling (diastole)
2) atrial contraction (diastole)
3) isovolumic ventricular contraction (systole)
4) ventricular ejection (systole)
5) isovolumic ventricular relaxation (diastole)
phase 1: ventricular filling (diastole) + ECG
AV valves open, ventricles filling. Semilunar valves closed. Flat line/beginning of P in ECG
phase 2: atrial contraction (diastole) + ECG
SA node fires, atria contract, P in atria higher than it was previously. Ventricles still filling. Semilunar valves still closed. End of P, Q+R waves on ECG
phase 3: isovolumic ventricular contraction (systole) + ECG
AV valves close as P in Ventricles> P in Atria. Semilunar valves still closed. S wave
phase 4: ventricular ejection (systole) + ECG
Semilunar valves open, volume ejection from ventricles to vessels. ST, beginning of T on ECG
phase 5: isovolumic ventricular relaxation (diastole) + ECG
Semilunar valves close as P in ventricles drops and ventricles relax.
Interval between systolic periods of the cardiac cycle ____ with increased parasym. drive
cardiac cycle length =
HR or RR interval
atrial pressure assoc. with atrial contraction
c wave ***
caused by change in atrial pressure as AV valves close and valve moves slightly back into atrium (pressure wave in atria during ventricular contraction during isovolumic phase)
end diastolic volume
volume in ventricle at end of diastole
what causes first heart sound?
mitral valve closing
pressure wave assoc. with Aortic valve closing
A measure of contractility. Ratio of blood ejected per beat (stroke volume) to volume of blood in the ventricles at the end of diastole (end-diastolic volume). EF = (EDV-ESV)/EDV
What causes 2nd heart sound?
aortic valve closing