Cardiac cycle Flashcards
1
Q
Cardiac cycle
A
Period from the beginning of one heart beat to the beginning of the next
Divided into systole and diastole
2
Q
Diastole
A
Ventricles fill with blood entering via the atria and venous system
To fill, ventricular pressure must be low - equivalent to that in venous system
3
Q
Systole
A
Ventricles eject blood into arterial system
To empty, ventricular pressure must be high, equivalent to that in arterial system
4
Q
Cardiac cycle is initiated by:
A
SA node
5
Q
Central venous pressure
A
Low (1-5 mm Hg)
6
Q
Arterial pressure
A
High (100 mm Hg)
7
Q
Cardiac cycle
A
Atria contract to eject blood to ventricles Bicuspid valve open Ventricles relaxed and full with blood Pressure on Ventricles low Bicuspid valve closes Ventricle contracts Pressure rises, 1st heart sound Pressure greater in ventricle Aortic valve opens Blood enters aorta Ventricle relaxes Aortic valve closes Pressure falls in ventricle 2nd heart sound
8
Q
2 heart sounds heard with stethoscope
A
1st "lub sound" longest and loudest Occurs at beginning of systole 2nd "dub" sound occurs at end of systole caused by closure of aortic and pulmonary valves
9
Q
Normal heart rate
A
75 bpm
10
Q
Cardiac cycle lasts
A
0.8 seconds
