Final answer:
The response to norepinephrine at an autonomic synapse is primarily terminated by reuptake into the presynaptic neuron, along with enzyme degradation and diffusion away from the synapse.
Step-by-step explanation:
The response to norepinephrine released at an autonomic synapse is terminated by either reuptake into the presynaptic neuron, diffusion away from the synapse, or degradation by enzymes. In the case of norepinephrine at an adrenergic synapse, the primary method of termination is reuptake by the presynaptic neuron, a process often assisted by the enzyme monoamine oxidase (MAO), which degrades any norepinephrine not reabsorbed into the neuron. These mechanisms ensure that the signaling is precise and does not overstimulate the target cells.