Homeostasis regulates the heart rate and all of its internal functions to maintain equilibrium. According to Biology Online, homeostasis uses a negative and positive feedback system to keep the human body running efficiently.
The portion of the brain stem that controls the heart rate is the medulla. The medulla transmits chemical messages and nerve impulses through the medulla pyramids. According to DHearts.com, the medulla pyramids are where all communication for the muscles, organs, and other areas of the body take place. During exercise and periods of high activity, the muscles in your body send messages through the brain stem to the medulla. The medulla then releases two hormones, epinephrine and norepinephrine, which travel through the brain stem to the heart. Once those two hormones reach the sinus node, they stimulate electrical impulses in the heart muscles and cause the heart muscle to contract faster.
When you stop exercising or decrease your level of activity, the muscles in the body send another message to the medulla to release acetylcholine.This hormone slows down the contractions of the heart, and allows the heart to rest by reducing the heart rate.
According to Biology Online, each beat of the heart pumps blood and oxygen to the muscles and organs of the body, so they can function properly. While oxygen is being delivered throughout the body, carbon dioxide is being removed to keep all of the cells, organs, muscles, and blood clean and healthy.