CARDIAC CYCLE Flashcards
what is the cardiac cycle
sequence of events that make up 1 heart beat
0.8 seconds per cycle
what is systole
contraction
what is diastole
relaxation
first stage of the cardiac cycle
diastole
0.5 seconds
atria fills and pressure rises
pushes the atrioventricular valve open
blood enters ventricles
atrium and ventricular walls relax
pressure in ventricles is lower than aorta and pulmonary artery
semilunar valves close
DUB sound
2nd phase of the cardiac cycle
atrial systole
0.15 seconds
muscular wall of atria contracts so remaining blood goes into the ventricles
muscular walls of ventricle still relaxed , they fill with blood
3rd stage of the cardiac cycle
ventricular systole
0.15 seconds
ventricle contracts after delay
pressure in ventricles is higher than atria
atrioventricular valves close
LUB sound
pressure in ventricles increases , forcing semilunar valves open
blood is pushed into the aorta and pulmonary artery
why do AV valves open
when pressure is higher in the atria compared to the ventricles
why do AV valves close
when pressure is higher in ventricles than atria
why do SL valves open
when pressure is higher in ventricles compared to arteries
why do SL valves close
when pressure is higher in arteries compared to ventricles
what is cardiac output
volume of blood pumped by 1 ventricle of the heart in one minute
what is stroke volume
volume of blood pumped out of the heart per beat
what is heart rate
beats per minute
equation for cardiac output
stroke volume * heart rate
what is an electrocardiogram
shows electrical changes in a heart during each heart beat
