Alpha adrenergic receptors are a type of adrenergic receptor that respond to the neurotransmitters norepinephrine and epinephrine. They are primarily found in the smooth muscles of blood vessels, where their activation leads to vasoconstriction, increasing blood pressure. These receptors are classified into two main subtypes: alpha-1 and alpha-2, each with distinct functions in the body. Alpha-1 receptors are mainly involved in promoting smooth muscle contraction, while alpha-2 receptors play a role in inhibiting neurotransmitter release, providing a feedback mechanism. Together, these receptors help regulate various physiological processes, including blood flow, heart rate, and overall sympathetic nervous system activity.