Cardiovascular Lecture 4 Flashcards
Where does atrial excitation begin and end?
Begins at SA node, ends at AV node. This is the P wave.
Where does ventricular excitation begin and end?
Begins with atrial relaxation (PQ) and ends when complete (PQRS)
What happens to the ECG with ventricular relaxation?
It is complete - PQRST.
What is EDV?
Volume in the venticle at the end of diastole
What is ESV
Volume in the ventricle at the end of systole
What is SV?
Volume ejected during systole. SV=EDV-ESV.
What is EF?
Ejection fraction, or fraction of EDV ejectd. EF=SV/EDV ~55-70%
Describe the steps of mechanical activity of the heart with respect to the opening and closing of valves.
1 &2 = systole 1. Ventricular contraction -AV valves closed -Aortic/pulmonary valves closed -Atria are relaxed -ventricles contract 2. Ventricular ejection -AV valves closed -Aortic/pulmonary valves open -Atria relaxed -ventricles contract 3&4 = diastole 3. Ventricular relaxation -AV valves closd -Aortic/pulmonary valves closed -atria relaxed -ventricles relaxed 4. Ventricular filling -AV valves open Aortic/pulmonary valves closed -atria contract -ventricles relax
Describe the overlap of electrical and mechanical activity.
During atrial excitation (P), ventricles are filling (diastole).
During ventricular excitation (PQRS), ventricles contract and eject.
During venticular relaxation (PQRST), ventricles relax/
What factors can alter cardiac mechanical function?
Preload, afterload, and contractility changes.
What determines valve status and blood flow?
Pressure changes
What does electrical excitation cause?
Myocardial contraction
What does myocardial contraction cause?
Pressure generation in atria and ventricles
What happens if preload is increased?
A greater volume is ejected/
What happens if afterload is increased?
Increased downstream pressure.
