Figure 3A. A cell with receptor sites that receive vital incoming
information from outside the cell. The signal can influence the cell to
perform myriad biological function.Neurotransmitters, neuropeptides, and hormones are the cause-and-effect
chemicals for brain activity and bodily functioning. These three different
types of chemicals, called ligands (the word ligare means “to bind” in
Latin), connect to, interact with, or influence the cell in a matter of
milliseconds.
— Neurotransmitters are chemical messengers that primarily send
signals between nerve cells, allowing the brain and nervous system to
communicate. There are different types of neurotransmitters, and each is
responsible for a particular activity. Some excite the brain, others slow it
down, while still others make us sleepy or awake. They can tell a neuron to
unhook from its current connection or make it stick better to its present
connection. They can even change the message as it is being sent to a
neuron, rewriting it so that a different message is delivered to all the
connected nerve cells.