PSC1002/L07 The Cardiac Cycle Flashcards
Define the cardiac cycle.
Cycle of pressure and volume changes in the heart chambers (both atria and ventricles) every time the heart contracts and relaxes
What are the 4 distinct phases of the cardiac cycle?
Ventricular filling
Isovolumetric ventricular contraction
Ventricular ejection
Isovolumetric ventricular relaxation
Define
1. Systole
2. Diastole.
- Contraction
- Relaxation
Describe late diastole (step 1).
Both sets of chambers are relaxed and ventricles fill passively
Describe atrial systole (step 2).
Atrial contraction forces a small amount of additional blood into ventricles
Describe isovolumetric ventricular contraction (step 3).
First phase of ventricular contraction pushes AV valves closed but does not create enough pressure to open semilunar valves
What is end diastolic volume (EDV)?
Maximum blood volume in ventricles
Describe ventricular ejection (step 4).
As ventricular pressure rises and exceeds pressure in the arteries, the semilunar valves open and blood is ejected
Describe isovolumetric ventricular relaxation (step 5).
As ventricles relax, pressure in ventricles falls
Blood flows back into cusps of semilunar valves and snaps them closed
Define end systolic volume (ESV).
Minimum blood volume in ventricles
Give the order in which valves open and shut during a heart beat.
Atrioventricular closes
Semilunar valve opens
Semilunar valve closes
Atrioventricular opens
What is the ejection fraction?
Stroke volume/end diastolic volume
What are the heart sounds caused by?
Closing of heart valves
What is the first and second heart sound?
1st - AV valves closing
2nd - SL valves closing
Give 2 diseases of valves.
Stenosis
Incompetence
