Alpha-1 receptors are a type of adrenergic receptor that play a crucial role in the body's response to norepinephrine and epinephrine. These receptors are primarily found on the smooth muscle cells of blood vessels, where their activation leads to vasoconstriction, increasing blood pressure. They are part of the sympathetic nervous system, which prepares the body for "fight or flight" situations. When alpha-1 receptors are stimulated, they also contribute to other physiological effects, such as pupil dilation and contraction of certain sphincters in the digestive system. Medications that target these receptors can be used to treat conditions like hypertension and nasal congestion by modulating blood flow and muscle tone.