Final answer:
The ß-adrenergic receptor is activated by adrenaline, leading to glycogen breakdown in liver cells through a process called glycogenolysis, and relaxation of smooth muscle cells as part of the "fight or flight" response.
Step-by-step explanation:
The receptor described in the question is the ß-adrenergic receptor, which plays a crucial role in the body's response to adrenaline (epinephrine). When adrenaline binds to the ß-adrenergic receptor on liver cells, it triggers a cascade of events leading to the breakdown of glycogen into glucose, thereby increasing the available energy sources for the body.
This process, known as glycogenolysis, is facilitated by the increase in cyclic AMP (cAMP) that activates protein kinase A (PKA). PKA then phosphorylates and activates enzymes involved in glycogen breakdown and inhibits enzymes involved in glycogen synthesis, preventing a futile cycle of degradation and synthesis.
In the context of smooth muscle cells, activation of the ß-adrenergic receptor results in the relaxation of the smooth muscles, part of the body's "fight or flight" reflex that prepares the body for rapid response to stress or danger. This relaxation is also a consequence of the increased cAMP levels, which lead to different cellular responses depending on cell type.