Cardiac Cycle iBook Flashcards
Why is the volume of the ventricles never @ 0?
there is always some blood in the ventricles
Describe the ECG
P wave=atrial depolarization
PR interval=time for AV node transmission
QRS complex=ventricular depolarization
ST segment=when ventricular mycytes @ plataeu
T wave=ventricular repolarization
What is the isoelectric line?
time btwn beats, when all chambers of heart are in diastole
When is peripheral run-off @ its lowest?
When is peripheral run-off @ its slowest?
@ start of ECG when low aortic pressure
total peripheral resistance is high & blood moves to periphery slowly
What is diastolic BP?
aortic pressure measured as blood ejected into aorta from L ventricle
aortic & ventricular pressures are almost equal
What is systolic BP?
peak of aortic pressure (after opening of aortic valve)
What is the dicrotic notch?
blip in aortic pressure wave produced by closing of aortic valve as ventricle relaxes
pressure in aorta then drops as blood goes into periphery
When does the aortic valve open?
when pressure in ventricle exceeds that of the aorta
When does ventricular pressure decrease
after the peak systolic pressure occurs
occurs quickly once aortic valve closes
Which pressure remains low throughout the cardiac cycle?
atrial pressure
When does the atrial pressure increase?
shortly after P-wave occurs due to atrial contraction
What is the c-wave?
small sharp increase in atrial pressure that coincides w/ start of ventricular contraction
What occurs during isovolemic/isovolumetric contraction?
ventricular pressure is increasingly rapidly & causes AV valve to bulge back into atria
leads to slight increase in atrial pressure
What is the v-wave?
increase in atrial pressure b/c AV valve is closed & venous blood is accumulating in atria
How does blood flow into ventricle from atria?
b/c during diastole & atrial systole, atrial pressure is greater than that inside the ventricle
What is the end systolic volume (ESV)
lowest volume of the ventricle (50mL of blood)
measured after aortic valve closes
What is the end diastolic volume? (EDV)
volume of blood in ventricle when ventricle is full
What is unique about the ventricular systole (isovolumetric contraction)?
ventricle is contracting isometrically to increase pressure b/c neither the AV nor the aortic/pulmonary valves are open
What is isvolemic relaxation?
when ventricular volume doesn’t change as ventricular pressure drops
aortic & pulmonary valves close before AV valves can open
When do the AV valves open?
when ventricular pressure drops below that in the atria
When does the first heart sound occur?
assoc w/ closing of AV valves (start of isovolemic contraction)
When does the second heart sound occur?
assoc w/ closing of aortic/pulmonic valves
when dicrotic notch occurs in aortic pressure wave
When does the third heart sound occur?
period of rapid filling & occurs early in diastole
When does the fourth heart sound occur?
assoc w/ blood being forced into ventricle during atrial contraction
