The nervous system detects stimuli, in this case, the ball. The eyes send a message through optic nerves to the brain, which in turn, sends a message through a motor neuron that causes the muscles to respond. Balance and coordination are needed as well and this is accomplished by the cerebellum portion of the brain. Voluntary muscles in the arm help to catch the ball. The circulatory system provides the necessary oxygen and glucose the cells need to have the energy to do this action. The heart increases its rate of pumping during exercise.
The muscular and nervous systems work together to catch the ball. The idea to catch the ball is formulated in the brain when the eye views the ball coming toward you. A signal is then sent to the brain through the optical nerves. Once the brain receives the signal, a new signal is sent to the muscles via the nerves, to the arm and hand, "telling" you to catch the ball.