Refer to Animation: Cell Signaling: Adrenaline Signaling in the Heart Muscle. Adrenaline stimulates an increase in heart rate by binding to: G proteins on the cytosolic face of the plasma membrane. adenylyl cyclase. regulatory regions in genes that code for muscle cell proteins. G protein-coupled receptors on the surface of heart muscle cells. nuclear transport proteins that allow adrenaline to be taken into the nucleus to act as a transcription factor.

The correct answer is ''G-protein coupled receptors on the surface of cardiac muscle cells.''

Explanation:

Adrenaline is a catecholamine whose pharmacological effects occur at alpha and beta adrenergic receptors. The mechanism of action of all beta adrenergic receptors is the activation of a G protein that activates adenylyl cyclase and increases cyclic AMP production. Adrenaline by b-adrenergic stimulus increases the contractile force of the myocardium (positive inotropic action) and increases the frequency in which the myocardium contracts (positive chronotropic action), consequently there is an increase in cardiac work, with a greater demand for oxygen due to the myocardium to be able to contract. Therefore, the blood flow to the heart is indirectly increased, bringing with it a greater supply of oxygen.