Question

why does the rate of heart beat increases during exercise or excitement?​

Answer 1

When you exercise, your muscles need even more oxygen because they are working harder. The faster your heart beats, the faster it can get more blood and oxygen to your muscles.  Fear causes the brain to release a chemical called adrenaline (uh-DREN-uh-lin), which speeds up your breathing and heart rate.

Answer 2

Answer:

due to flow of blood is increased.