There are eight systems in the human body. Each system relies on the other to keep the body functioning. The systems of the body includes the circulatory, immune, skeletal, excretory, muscular, endocrine, digestive, nervous and respiratory.It is important to understand how human body systems work together.ervous System. The body has connectors neurons that communicate signals throughout the body. Messages are sent through nerves called neurons that are responsible for communication in the body. The nervous system controls the body's sense of smell, hearing, tasting, seeing and touching.