The stimulation of sympathetic cardiac nerves increases the rate of action potential generation from the sinoatrial (SA) node of heart. The following statements suggest the mechanism of this action:
A. The depolarizing effect of 'h' current (lh) is decreased by sympathetic stimulation.
B. Norepinephrine secreted by the sympathetic endings binds to β1 adrenoceptors resulting in the increase of intracellular cAMP.
C. The increased intracellular cAMP facilitates the opening of long-lasting (L) Ca++ channels.
D. The Ca++ current (Ica) due to the opening of voltage-gated L Ca++ channels is decreased.
Which one of the following options represents the correct combin ation of the statements?
1
A and B
2
B and C
3
C and D
4
A and C