The carotid sinus is a small dilation located at the base of the internal carotid artery, near where it branches from the common carotid artery. It plays a crucial role in regulating blood pressure by detecting changes in blood flow and pressure. When blood pressure rises, the carotid sinus sends signals to the brain to help lower it, often by slowing the heart rate or dilating blood vessels. This feedback mechanism is essential for maintaining stable blood pressure and ensuring proper blood flow throughout the body.