Axon sends the message. Dendrite receives it.
When you hold your breath what sends the message to your brain is your neves.
It depends what the message is.
your nervous system sends messages to the brain like when you move your arm you nervous system sends the message to the brain
myelinated
The secret message sends messages secretly.
Retina
When you want to move a muscle, your brain sends a message out to the muscle you want to move, and the muscle sends a message back to your brain that your moving it and where.
Your afferent neurons send a message to your brain.
It sends the message to your brain of what your seeing
Afferent
The sender. (The terms messenger and message are applied to the carrier of messages.)