What’s the meaning of “sympathetic” and “parasympathetic”?

sympathetic: relating to or denoting the part of the autonomic nervous system consisting of nerves arising from ganglia near the middle part of the spinal cord, supplying the internal organs, blood vessels, and glands, and balancing the action of the parasympathetic nerves

parasympathetic: relating to the part of the automatic nervous system that counterbalances the action of the sympathetic nerves. It consists of nerves arising from the brain and the lower end of the spinal cord and supplying the internal organs, blood vessels, and glands.

Explanation:

a symbiotic relationship with the mitochondria