Chemical messengers: Neurotransmitters
Neurons (nerve cells) are one of the building blocks of behavior. It is estimated that there are between 10 and 100 billion neurons in the nervous system and that neurons make 13 trillion connections. The neurons send electrochemical messages to the brain so people can respond to stimuli—either from the environment or internal changes in the body. A chemical messenger called a neurotransmitter is released as part of...