how’s the volume decreasing and how is there that particular pressure variation seen?
Pressure in the ventricle rises during systole leading to ejection of blood into aorta. This causes volume of blood in the ventricle to decrease
What is done here is
Step 1 …fill the ventricle with a volume of blood ,say 50 ml ,then 100, 150,200 ,250ml and call it filling volume(as shown on" x axis")
Step 2 measure left ventricular pressure ,when ventricle is contracting
Step 3 plot a graph between LV pressure and “filling volume”…50 ,100,150,200,250ml as shown in diagram
Result of the experiment
As “filling volume(term used in experiment)” or End diastolic volume increases, force of ventricular contraction also increases, according to frank starling law .
Force of contraction reaches max value at filling volume/EDV of 150 to 170 ml.
At higher filling volumes like 250 ml …force of contration decreases . …because at these great volumes the actin and myosin filaments of cardic muscles are pulled apart far enough that the strength of eqch cardiac fibre contraction becomes less than optimal.
I explained only systolic part