Final answer:
The axon terminals (synaptic knobs) are the specific part of the neuron that communicates with a target cell and serves as the secretory region of the cell.
Step-by-step explanation:
The specific part of the neuron that communicates with a target cell and serves as the secretory region of the cell is the axon terminals (synaptic knobs). Axon terminals are the small branches at the end of the axon that transmit electrical signals to the target cell, usually through the release of neurotransmitters.