Beta adrenergic receptors are a type of protein found on the surface of cells that respond to hormones like epinephrine and norepinephrine. They play a crucial role in the body's response to stress, helping to regulate heart rate, blood pressure, and energy metabolism. There are three main subtypes: β1, β2, and β3, each with different functions and locations in the body. When activated, beta adrenergic receptors trigger a series of cellular responses that prepare the body for "fight or flight" situations. For example, β1 receptors primarily affect the heart, increasing heart rate and contractility, while β2 receptors are involved in relaxing smooth muscles, such as those in the airways.