APA Dictionary of Psychology

a neural circuit that is involved in a reflex. In its simplest form, it consists of an afferent, or sensory, neuron that conducts nerve impulses from a receptor to the spinal cord, where it connects directly or via an interneuron to an efferent motor neuron that carries the impulses to an effector, that is, a muscle or gland. See also disynaptic arc; monosynaptic arc; polysynaptic arc.