Physiology 3120 Lecture Notes - Lecture 16: Pulmonary Vein, Aortic Valve, Heart Valve

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Stavraky Lecture 16
-cardiac cycle consists of events that occur during one contraction-relaxation period (shown
here are two systoles with one diastole)
-one ventricular diastole when ventricles relax  heart is in diastole quite a long time
-one ventricular systole when ventricles contract  heart is in systole quite a short time
-there is atrial diastole/systole as well but traditionally cardiac cycle goes by ventricular
diastole/systole
-cycle begins with AP generated at SA node  can see two P waves in ECG at the bottom
-AP then spreads through atrial muscle cells through AV node and Bundle of His down to
ventricular muscle cells and causes the ventricles to contract
-keep in mind the sequence of events as go through cardiac cycle
-pressure changes in aorta shown by top dashed line in pressure graph  keeps going up and
down
-pressure changes in LA shown by bottom dashed line in pressure graph  is not going up and
down as much as aorta
-pressure changes in LV shown by solid line in pressure graph  creates lots of pressure to go
way up and then comes down and so on
-can see corresponding events so during ventricular systole (contract) pressure increases for
short time and then ventricular diastole (relax) pressure decreases for long time
-pressure changes important to move around blood
-volume changes in LV going down with pressure increase and going up with pressure decrease
-ECG have seen before
-Phonocardiogram shows sounds that heart makes ie: lub-dub
-atrial systole  atrium contracts
-protodiastole  early diastole
-starts at P wave where depolarization causes atrium to contract
-as atrium contracts, pressure in atrium rises and can see atrial pressure is higher than
ventricular pressure
-at this point AV valves are already open so last 30% of blood is pushed into ventricle from
atrium  can see ventricular volume rising
-other 70% of ventricular filling has already occurred in previous cycle
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