how does the nervous system help the body maintain homeostasis? if it doesn't function correctly how does it affect the body?

Homeostasis is maintained at many levels, not just the level of the whole body as it is ... Of course, body temperature doesn't just swing above its target value

the relative atomic mass of an element is the mass of one atom of that element, relative to 1/12th of the mass of a  1212c atom. to convert to an absolute mass in kg, it is necessary to multiply by  1.661×10−271.661×10−27.

the relative atomic mass is roughly equal to the number of neutrons, plus the number of protons, in the nucleus of the atom.

for elements with more than one stable isotope (different types of nucleus with different numbers of neutrons but the same number of protons), the quoted mass is usually the average mass, weighted by the relative abundance of the different isotopes.