Figure 35.1: Chemical Signaling by Nerve and Endocrine Cells Both nerve cells (neurons) and endocrine cells release chemical signaling molecules (red dots) that affect target cells. (A) A nerve cell makes synaptic contact with a target cell at the end of its axon. Action potentials in the axon trigger release of neurotransmitter molecules at the synapse. These molecules then bind with neurotransmitter receptor molecules in the postsynaptic cell, initiating a response in the postsynaptic cell. (B) An endocrine cell releases hormone molecules into the blood. These molecules circulate throughout the body and bind with hormone receptor molecules on target cells, initiating responses.