Cardiac Cycle and it's Control (Fri 20th) Flashcards
Cardiac Cycle?
- Ventricular filling, atrioventricular valves are open but the semi-lunar valves are closed. DIASTOLE
- Atria contract, atrioventricular valves are open but the semi-lunar valves are closed. DIASTOLE
- Isovolumnic contraction: (Both AV & SL closed) SYSTOLE, but the ventricle is contracting, so called isovolumetric because the volume of blood doesn’t change but the pressure in the ventricle does.
- Ventricular Ejection (AV closed, SL open). SYSTOLE, SL opens once pressure in ventricle greater than pressure in aorta / pulmonary artery
- Isovolumic Relaxation (both AV & SL closed) DIASTOLE
Max and min pressure changes in aorta?
Maximal during systole (peaks at ~120 mmHg), which declines to a minimum during diastole (lowest ~80 mmHg).
How to calculate stroke volume?
End-diastolic volume, End-systolic volume (residual volume).
Stroke volume, SV = EDV-ESV
What is the ejection fraction?
Ejection fraction = SV/EDV, normally about 0.6.
What causes the first and second heart sounds (ba- dump)?
- atrioventricular closing
2. semilunar opening
What is a phonocardiogram?
a chart or record of the sounds made by the heart.
Dichrotic notch?
where the semilunar valve closes causing a slight rebound of blood in aorta.
Mean Atrial Pressure
DP plus a third (SP-DP)
Diseases of the valves?
- Incompetence: leaky, don’t close properly.
2. Stenosis: narrowing