Cardiac Cycle Flashcards
what is the cardiac cycle
a complete heartbeat
atrial and ventricular systole and diastole
how long is heart beat
0.8seconds
explain diastole
The atria and ventricles relax and blood flows into the atria of heart from the veins.
At the beginning of diastole the AV valves are closed. As pressure builds in the atria that forces open the AV valves and blood flows into the ventricles.
explain atrial systole
Both atrial walls contract pushing blood into the ventricles
Once the ventricles are full of blood ventricular systole begins
explain ventricular systole
As the ventricular walls start to contract this builds pressure up to the point where it will force the AV valves closed.
As pressure continues to build the semi-lunar valves open.
Blood flows into the arteries (aorta and pulmonary artery).
what is lub sound
av valve closing as ventricles contract (close as blood forced against them)
what is dub sound
semilunar valves closing as ventricles start to relax (closed due to backflow blood)
what is stroke volume
volume of blood pumped by the heart in one cardiac cycle
80cm3
inc during exercise
what is cardiac output
stroke volume x heart rate
why do AV close vs open
pressure in the ventricles rises above the pressure in the atrium
pressure in the atrium rises above the pressure in the ventricle
why do semilunar valve open and close
pressure in the ventricle rises above pressure in the aorta
pressure in the aorta rises above pressure in the ventricle
factors impact heart rate
Adrenaline
Levels of respiratory gases in the blood
Blood pressure - mechanism prevents heart rate increasing further
role tendinous cords
stop AV valve invert
tricuspid vs bicuspid valve
between R atrium/ventricle
3 cusps - same vol but lower pressure hence need to open more for more volume
between L atrium/ventricle
2 cusps
