Stimulation of mu receptors exerts effects that depress nerve impulse transmission.

Morphine acts on the central nervous system to produce both depression and euphoric stimulation, effects that are mediated through its stimulation of mu opioid receptors.

Mu receptors' activation in some instances inhibits the transmission of inhibitory impulses, thereby causing stimulation.

Morphine has a marked analgesic effect because of its stimulation of mu receptors in both the brain and spinal cord, and its principal therapeutic value is for the relief of moderate to severe pain.