What role does the nervous system play in keeping the human body alive?

What role does the digestive system play in keeping the body alive?

• I've pondered this question but couldn't come up with a staight answer. Can you answer this in detail?

• Answer:

  Humans are not autotrophs and therefore we do not make our own food. We have to ingest things in order to get energy so that our body can do work. We use what we get from food to do cellular respiration, which fuels the body. Without energy, the body couldn't perform basic functions, and the body would start to look for other sources of energy. It would use our fat tissue first and then start eating away at our muscle tissue (including our heart) until we died. So, therefore, we need our digestive system to extract necessary molecules from the food we eat. The excretion of waste products is also important, as it would be bad if wastes built up in our bodies instead of being excreted.