1. Phosphorylation of phospholamban by PKA increases the activity of SERCA2a. Wh

Question

1. Phosphorylation of phospholamban by PKA increases the activity of SERCA2a. What is the result if heart rate stays the same and the level of phospholamban phosphorylation increases?

a) SR Ca concentration decreases, amount of SR Ca released decreases, and developed force decreases

b) SR Ca concentration decreases, amount of SR Ca released stays same, and developed force decreases

c) SR Ca concentration increases, amount of SR Ca released stays same, and developed force stays the same

d) SR Ca concentration increases, amount of SR Ca released decreases, and developed force stays the same

e) SR Ca concentration increases, amount of SR Ca released increases, and developed force increases

2. The major force favoring fluid filtration from the capillaries into the interstitial fluid

a) capillary hydrostatic pressure

b) capillary oncotic pressure

c) interstitial fluid hydrostatic pressure

3. At very low flow rates, the concentration of a diffusible metabolite within a capillary

a) goes to 0

b) increases for all time

c) approaches the interstitial concentration of the metabolite

d) approaches the rate of metabolism of the metabolite Qm, divided by E

Explanation / Answer

1.The correct answer is : e )SR Ca concentration increases, amount of SR Ca released increases, and developed force increases.

Reason:Phosphorylation of phospholamban by PKA prevents phospholamban to inhibit the activity of SERCA2a .This results in activation of SERCA2a and an increase in Ca , resulting in more contraction which is also known as positive inotropic effect.

2.The correct answer is: c) interstitial fluid hydrostatic pressure.

Reason:This is the pressure that favours the movement of fluid and solutes from the capillary into the interstitial fluid.

3.The correct answer is : b) increases for all time.

Reason:Even at low rates, there is an increase in the concentration of a diffusible metabolite within a capillary for all time.

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