Affector (noun)
A nerve cell that directly activates a muscle
Effector (noun)
Any muscle, organ etc. that can respond to a stimulus from a nerve.
Effector (noun)
The part of a nerve that carries a stimulus to a muscle etc.
Effector (noun)
Any small molecule that effects the function of an enzyme by binding to an allosteric site.
Effector (noun)
An actuator.
Wiktionary
Effector (noun)
an organ or cell that acts in response to a stimulus
“effector cells”
Oxford Dictionary