Adrenergic Receptors:Adrenergic receptors are a class of G protein-coupled receptors that bind to the neurotransmitters epinephrine (adrenaline) and norepinephrine (noradrenaline).
$\beta$ Receptors: $\beta$ receptors are a subtype of adrenergic receptors that are further classified into $\beta_1$, $\beta_2$, and $\beta_3$ subtypes, each with distinct functions and distributions in the body.
Sympathetic Nervous System:The sympathetic nervous system is one of the two divisions of the autonomic nervous system, responsible for the body's 'fight-or-flight' response, including the activation of $\beta_2$ receptors.