Why does your heart rate change during exercise?

Why does exercise change your heart rate? It changes your heart rate with muscle cells by when cells work harder and faster it gives your body more energy which makes you move more. Opposite of when you are asleep you don't move as much. The process cells use to produce energy (ATP) that cells all work together at the same time it creates more energy for your body. Cellular Respiration gets the raw ingredients it needs by when you swallow your food it goes down your esophagus into your digestive system which is part of cellular respiration. The cardiovascular system brings these materials to the cells by digesting the materials into tiny little pieces so it can flow through your body into your cells. My own target and maximum heart rate is one-hundred-and-four to one-hundred-seventy-seven, this is my target zone. My maximum heart rate is two-hundred-seven. You find out your heart rate by deducting your age from two-hundred-twenty-two. Those are MY personal target zones and heart rates. This is why exercise changes your heart rate.

do not use this information for any homework background paragraphs because i do not know if it is correct it most likely isn't