Final answer:
The effects of epinephrine and norepinephrine released by the suprarenal glands last longer due to their prolonged circulation in the bloodstream.
Step-by-step explanation:
The effects of epinephrine and norepinephrine released by the suprarenal glands last longer than when released at neuroeffector junctions because of the differences in their mechanisms of action.
When released at neuroeffector junctions, epinephrine and norepinephrine quickly bind to receptors on target cells, causing immediate changes in cell function. However, their effects are short-lived as they are rapidly metabolized and cleared from the synapse.
On the other hand, when released by the suprarenal glands, epinephrine and norepinephrine enter the bloodstream, allowing them to reach and affect distant target organs. This prolonged circulation in the body extends their effects, resulting in a prolonged physiological response.