Assertion (A) Chemical messengers are chemicals that enable communication of message between two neurons or between neurons and muscles.Reason ( R) Chemicals enter the cell through receptor only.

In the body, message between two neurons and that between neurons to muscles is communicated through certain chemicals. These are called chemical messengers that are received at the binding sites of receptor proteins. To accommodate a messenger, the shape of receptor site gets changed. This brings about the transfer of message into the cell. Thus, chemical messenger gives message to the cell without entering the cell.