Chemical messages, also known as neurotransmitters, originate from neurons, which are the fundamental units of the nervous system.

Here's a breakdown:

* Neurons: These specialized cells are responsible for transmitting information throughout the body. They have a unique structure with a cell body, dendrites (which receive signals), and an axon (which transmits signals).

* Synapse: The junction between two neurons is called a synapse. This is where chemical messages are exchanged.

* Neurotransmitter release: When a neuron is stimulated, it releases neurotransmitters from tiny sacs called vesicles at the end of its axon.

* Neurotransmitter receptors: These receptors are located on the dendrites of the receiving neuron. They bind to specific neurotransmitters, triggering a response in the receiving neuron.

So, in summary, chemical messages originate from neurons and are released at the synapse to communicate with other neurons.

It's important to note that chemical messages are not limited to neurons. Hormones, which are produced by glands, also act as chemical messengers throughout the body.