β1, or beta-1 adrenergic receptor, is a type of protein found in various tissues, particularly in the heart. It plays a crucial role in the body's response to stress by binding to hormones like epinephrine and norepinephrine. This interaction helps regulate heart rate and contractility, making it essential for maintaining cardiovascular function. In addition to its role in the heart, β1 receptors are also present in the kidneys, where they influence renin release, affecting blood pressure and fluid balance. Understanding β1 receptors is important for developing treatments for conditions like heart failure and hypertension.