General Physiology

Question 1

What is the next ATP gain per molecule of glucose following aerobic metabolism

Answer 1

38 ATP

Question 2

Outline Fick’s principle

Answer 2

VO2 = CO x (CaO2 - CvO2)

Uptake of a substance is equal to the flow multiplied by the difference in arterial and venous concentrations of that substance.

M = Q x (A-V)

Question 3

What are the four phases of the cardiac action potential in contractile cells

Answer 3

Phase 0 - Fast sodium influx
Phase 1 - Activation K channels with potassium efflux
Phase 2 - Activation calcium channels, with calcium influx, and ongoing potassium efflux causing potential to remain the same
Phase 3 - Calcium channels close, potassium efflux continues causing membrane potential to return to -90
Phase 4 - Rest period, no change in potential

Question 4

What is the partial pressure of oxygen in the umbilical vein

Answer 4

Partial pressure O2 in the umbilical vein is 4.7kPa - this is the blood being delivered to the foetus.

Question 5

Outline foetal circulation

Answer 5

Two umbilical arteries and one umbilical vein; vein delivers oxygenated blood from mother to foetus.
Ductus venous means 50-60% of this venous blood bypasses the hepatic circulation, entering IVC.
At junction of IVC and RA, the eustachian valve directs highly oxygenated blood across the foramen ovale into the LA. Sats 60% at this point.
Majority of LV blood delivered to brain and coronary circulation.
Because of high PVR, most blood from right ventricle crosses ductus arteriosus entering the descending aorta.

Question 6

What is a normal haemoglobin profile

Answer 6

HbA 95-98%
HbS - 0% (sickle)
HbC - 0% (sickle cell C)
HbF - <1%
HbA2 - <3 - 5%

Question 8

Oxygen content equation

Answer 8

((Hb g/dl) x 1.34 x SpO2) + ( 0.0225 x PaO2)

Question 9

Oxygen delivery formula

Answer 9

DO2 = cardiac output x oxygen content