Final answer:
Substances that create an osmotic effect in the intestines, such as osmotic diuretics or excessive glucose in diabetes mellitus, can stimulate water absorption and intestinal peristalsis. Insoluble fiber also promotes the movement of waste through the intestine by stimulating peristalsis.
Step-by-step explanation:
Intestinal peristalsis is stimulated by the presence of substances that create an osmotic effect, leading to water retention in the bowel. For example, osmotic diuretics like mannitol increase water excretion but are not absorbed in the gut, triggering an increase in the osmotic pressure that draws water into the intestinal lumen. Similarly, in poorly controlled diabetes mellitus, excessive glucose levels cause glucose to appear in urine, exhibiting a diuretic effect due to its osmotic properties. This osmotic effect can also stimulate the absorption of water in the intestines, as seen with V. cholerae infection where the bacteria-produced toxin increases cAMP levels in intestinal cells, opens chloride channels, and draws water into the intestinal lumen, resulting in severe diarrhea.
Insoluble fiber, such as cellulose, also enhances peristalsis by adding bulk to stools and stimulating the involuntary contractions that move food waste through the intestine, aiding in the prevention of constipation. The large intestine also serves important functions in water, electrolytes, and nutrient absorption, further compacting the waste and leading to feces elimination.