Homeostasis: The ability of an organism or system to maintain stable internal conditions despite changes in external conditions.
Neurotransmitters: These are chemical messengers used by neurons (nerve cells) to transmit signals across a synapse (the gap between two neurons).
Endocrine System: A network of glands in your body that make hormones which help cells talk with each other. They're responsible for almost every cell, organ and function in our bodies.