Final answer:
Activating mu receptors in the gut can cause constipation due to decreased smooth muscle motility and diarrhea due to increased fluid and electrolyte secretion.
Step-by-step explanation:
Activating mu receptors in the gut can lead to several adverse effects. One of the effects is a decrease in the motility of smooth muscle in the gastrointestinal tract, which can cause constipation. Additionally, activating mu receptors can also result in the activation of adenylate cyclase in intestinal cells, leading to increased levels of cyclic adenosine monophosphate (CAMP) and the secretion of fluids and electrolytes out of the cell, causing diarrhea.