How does the body respond to changes in its environment

Receptors are groups of specialised cells. They detect a change in the environment stimulus. In the nervous system this leads to an electrical impulse being made in response to the stimulus. Sense organs contain groups of receptors that respond to specific stimuli.

the relative standard reduction potential of the half-cell in which reduction occurs; more positive than the other half-cell. reduction is a chemical process in which electrons are added to an atom or an ion; it always occurs accompanied by oxidation of the reducing agent.

a symbiotic relationship with the mitochondria