Physio tidbits

Question 1

Von Bezold-Jarisch reflex

Answer 1

triggered stretch receptors in inferioposterior LV wall trigger powerful vagal response => bradycardia and hypotension

Question 2

Bernheim effect

Answer 2

dilation and volume overload of LV so great that it compromises RV filling (also vice versa = “reverse Bernheim”)

Question 3

Law of Laplace

Answer 3

Wall stress (Tension) = Pressure x radius/2 x wall thickness – all values at end-diastole (stress = tension applied to cross-sectional area)

Question 4

Compliance (dV/dP)

Answer 4

distensibility (diastolic pressure required to fill the ventricle to same volume), extent at which the aorta can “yield” during systole – Opie 2004

Question 5

Impedance

Answer 5

index of afterload and is aortic pressure divided by aortic flow at that instant (Opie 2004)

Question 6

Major determinants of myocardial O2 demand

Answer 6

HR, wall stress, Vmax (contractility)

Question 7

Bowditch phenomenon (Treppe effect)

Answer 7

increase in HR = increase in force of contraction – thought to be secondary to excess Na and Ca enter cell than can be handled by Na pump  increased Ca d/t Na/Ca exchanger  increased contractility