muscular contraction.

The hormone adrenaline binds to specific receptors on the surface of cells, activating an enzyme called adenylate cyclase. This enzyme then activates the production of a second messenger molecule called cyclic AMP (cAMP). cAMP then triggers a series of reactions that lead to the release of calcium ions from intracellular stores. The increase in intracellular calcium induces muscle contraction, resulting in increased heart rate and blood pressure, as well as other physiological responses associated with the “fight or flight” response.