Neurotransmitters can transmit signals from a neuron to non-neuronal effector cells, such as muscle cells or gland cells.

This statement is **true**. The definition specifies a signal crossing a synapse from one neuron to another target neuron. The neuron-to-neuron destination is a key part of the definition provided, rather than an optional detail.\n\n**Key takeaway:** The stated target of neurotransmitter signaling is another neuron.\n\n**Glossary:** **Neuron**: A nerve cell; **synapse**: A junction between a signaling neuron and its target.