Because neurones will not function properly neither will neuroreceptors if a person lacks neurotransmitters, these two parts (transmiters and receptors) all work together and depend on eachother.
Neurones are resposible for transmitting informations trought the body, and if neurotransmitters are no-existent, information may not be able to get to some body parts since neurotransmitters transmit the information.
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