Adrenergic receptors are a type of protein found on the surface of cells that respond to the hormones epinephrine and norepinephrine. These receptors play a crucial role in the body's response to stress, regulating functions such as heart rate, blood pressure, and airflow in the lungs. There are two main types: alpha and beta receptors, each with different effects on various tissues. When epinephrine binds to these receptors, it triggers a series of cellular responses that prepare the body for "fight or flight" situations. For example, beta-1 receptors increase heart rate, while alpha-1 receptors cause blood vessels to constrict. This complex system helps maintain homeostasis during physical and emotional stress.