SS2. Cardio vascular system - preload

Question 1

What is preload?

Answer 1

left ventricular wall stress at the end-diastole.

Question 2

How is elastance calculated?

Answer 2

pressure / volume

Question 3

How is wall stress calculated?

Answer 3

(PxR) / 2x wall thickness
Rtot = Rin + W
Volume = wortel3(3V/4Pi)

Question 4

What happens when the pressure/wall stretch goes up?

Answer 4

The preload and stretching of heartcells goes up.

Question 5

How to calculate preload?

Answer 5

(Ped x Red) / 2x Wed

Question 6

What causes stretching?

Answer 6

1) Frank-starling mechanism. Myosin heads with overlapping actins, can only bind in 1 direction bc of its polarity. When myosin is stretched out, you have more myosins at work
2) inotropic mechanism: Actin guarded by tropomyosin. Toponin (C,I,T) scootches tropomysin away. When stretching, troponin C stretched out, works differently and binds calcium, resulting in bigger effect of calcium.