Re: What system is the body most dependent on?

The question that you pose is a rather difficult one to answer. The simple answer is that all of the body systems are important (and necessary) for normal functioning and survival. The body systems include the circulatory system, the endocrine system, the immune system, the digestive system, the lymphatic system, the musculoskeletal system, the nervous system, the reproductive system, the respiratory system and the urinary system. Out of all of the body systems, the nervous system would probably have to be considered the most important system; the nervous system is the major regulatory and communication system in the body. For example, the nervous system contains sensory receptors which help us regulate our body temperature, blood pH, and carbon dioxide concentration in the blood. If the nervous system didn't help regulate homeostasis and facilitate communication between systems, human life would not be able to exist.

[Note however, that the nervous system is highly dependent on all of the other systems that Chris mentioned for its own function. -- Moderator]