Muscle physiology is the study of how muscles function and produce movement. Muscles are made up of cells called muscle fibers, which contract in response to signals from the nervous system. This contraction allows for various activities, from simple movements like walking to complex actions like playing sports. There are three main types of muscles: skeletal muscle, smooth muscle, and cardiac muscle. Skeletal muscles are under voluntary control and help with movement, while smooth muscles control involuntary actions in organs. Cardiac muscle, found only in the heart, is responsible for pumping blood throughout the body.