Final answer:
Alpha-1 adrenergic receptors are located on smooth muscles and are activated by adrenaline or noradrenaline, causing smooth muscle contraction and effects like vasoconstriction. They regulate vascular tone and blood pressure, and are targets for medications controlling blood flow and pressure.
Step-by-step explanation:
Alpha-1 adrenergic receptors are G protein-coupled receptors found mainly on smooth muscles of various tissues, including blood vessels, eye, heart, and prostate. Activation of these receptors by their ligands, adrenaline, or noradrenaline results in smooth muscle contraction, leading to effects such as vasoconstriction, decreased motility of the gastrointestinal tract, and increased peripheral resistance.
They accomplish this by coupling to the Gq protein, resulting in increased intracellular calcium levels. This receptor subtype also induces glycogenolysis and gluconeogenesis, primarily in the liver and adipose tissue, and promotes Na+ reabsorption in the kidneys.
In addition to their role in the fight-or-flight response, alpha-1 adrenergic receptors have a significant function in maintaining vascular tone and blood pressure regulation. They sense blood pressure changes via baroreceptors and play a role in the autonomic regulation of various organ systems, a process known as autonomic tone. Alpha-1 adrenergic receptors are also a pharmacological target for certain medications that aim to modulate blood flow and blood pressure.