Chemical messengers are generally called neurotransmitters when they are involved in the nervous system.

However, there are other types of chemical messengers, and they can have different names depending on their function and where they act:

* Hormones: These are chemical messengers produced by glands and transported in the bloodstream to target cells.

* Cytokines: These are proteins produced by immune cells that act as messengers between cells.

* Growth factors: These are proteins that stimulate cell growth and differentiation.

* Local mediators: These are chemical messengers that act on nearby cells.

So, while "neurotransmitter" is the most common term, there are other terms used depending on the specific type of chemical messenger and its function.