Name three reasons why the nervous system is one of the most important system in the body?

First of all, the nervous system is like the central commanding centre of the body. Your breathing rate, homeostasis, your muscle movement - almost all systemic activities are regualted by the nervous system. When the nervous system gets disconnected from the rest of the body as in the case of a break in the spinal cord (for example), paralysis can occur. This is because the body as a whole needs instructions and these instructions have to be given by some organ/organ system.

Take for example, a simple problem like dehydration. Your blood volume can decrease, which means your blood pressure can fall. When such an event occurs, hormones are secreted via a cascade to allow retention of more quantity of water from the kidney while filtration, allowing your blood volume to come back to some semblance of normalcy.

So, each little environmental or internal event that can hamper the normal functioning of the body is counteracted by the decisions of the nervous system. Even muscular movement, especially involuntary, could not occur without the guidance of the nervous system. As such, the nervous system is the most important system in the body.