DNA has a negative charge because of the phosphate ions in its chemical backbone.
Homeostatic regulation involves three parts or mechanisms: 1) the receptor, 2) the control center and 3) the effector. The receptor receives information that something in the environment is changing. The control center or integration center receives and processes information from the receptor.
The principle of homeostasis is the central theme of this text and the foundation of all modern physiology. Homeostatic regulation is the adjustment of physiological systems to preserve homeostasis.