Alpha receptors are a type of adrenergic receptor that respond to neurotransmitters like norepinephrine and epinephrine. They are primarily found in the smooth muscles of blood vessels, where their activation leads to vasoconstriction, increasing blood pressure. There are two main subtypes: alpha-1 and alpha-2 receptors, each with distinct functions in the body. Alpha-1 receptors mainly mediate the contraction of blood vessels and other smooth muscles, while alpha-2 receptors play a role in inhibiting neurotransmitter release, which can decrease blood pressure. These receptors are important in various physiological processes, including the regulation of blood flow and the body's response to stress.