Beta-1 Adrenergic Receptor Effects in Cardiac Myocytes

Question 1

What 4 ways can beta-1 adrenoreceptor stimulation support cardiac performance?

Answer 1

1. Positive inotropy
2. Positive lusitropy
3. Positive chronotropy
4. Positive dromotropy

Question 2

Stimulation of beta-1 GPCR on cardiac myocytes results in what intracellular response?

Answer 2

Activates adenylyl cyclase > increases cAMP

Question 3

Protein kinase A (PKA) phosphorylates what sites in the cardiac myocytes?

Answer 3

L-type Ca++ channels in the plasma membrane

Phospholamban

Tnl

Question 4

Phosphorylation of L-type Ca++ channels results in:

Answer 4

Ca++ influx (positive inotropy)

Question 5

Phosphorylation of phospholamban results in:

Answer 5

Relieved SERCA2 pump inhibition (positive lusitropy) and makes more Ca++ available for release (positive inotropy)

Question 6

Phosphorylation of L-type Ca++ channels and phospholamban in SA nodal cells leads to:

Answer 6

Increased intracellular Ca++ > increased rate of phase 4 depolarization (positive chronotropy)

Question 7

Phosphorylation of L-type Ca++ channels and phospholamban in AV nodal cells leads to:

Answer 7

Increased intracellular Ca++ > enhanced excitability and firing > increased conduction velocity through AV node (positive dromotropy)