Figure 1. Graphical representation of the intracellular signaling cascade following activation of the G‐protein coupled β₁‐adrenergic receptor in cardiac tissue.

Mediated through the stimulatory (Gs) component of the β₁‐adrenergic receptor, activation of the adenyl cyclase pathway occurs with a resulting increase in cAMP (cyclic adenosine monophosphate) and subsequent increased intracellular calcium cycling. The altered calcium handling results in a positive chronotropic response, increased myocardial contractility, and lusitropy. PLB indicates phospholamban; RyR, ryanodine receptor; SERCA, sarco/endoplasmic reticulum Ca²⁺ ATPase; and SR, sarcoplasmic reticulum.