what system sends the body signal
The size of the nervous system ranges from a few hundred cells in the simplest worms, to around 300 billion cells in African elephants. The central nervous system functions to send signals from one cell to others, or from one part of the body to others and to receive feedback. Malfunction of the nervous system can occur as a result of genetic defects, physical damage due to trauma or toxicity, infection or simply of ageing.