A: According to our notes, Cholecystokinin increases stomach motility. However, in Guyton's Med. Physiology book, it says it's an inhibitor of stomach motility. It also says it is a competitive inhibitor to block the increased stomach motility caused by gastrin. My question is, what is CCK's function on the stomach?? You're right. I'm not sure how that got into the notes - CCK may be a weak agonist by itself but competitively blocks gastrin-stimulated stomach motility (similar to what it does to gastrin-stimulated acid secretion). Regardless, the effect listed in my notes should be inhibition of gastric motility.

2. Q: What is the difference between propagation and propulsive action of the small intestine? What is the difference between propagation and propulsive action of the small intestine?

    A: In the context of the small intestine, propagation refers to migration of the slow wave from it's site of origin which could be anywhere. When slow wave migration is associated with a ring of contraction, one might speak of a propagated contraction. Propulsive action refers specifically to the movement of chyme whether it be due to a propagated ring of contraction or the cumulative effect of stationary contractions (rhythmic contractions). The latter would be only slowly propulsive.

3. Q: Why is atropine less effective in decreasing salivation in the cat? Why are atropine and other parasympatholytic drugs less effective in drying up the mouth in the cat than in the dog?

     A: Atropine blocks parasympathetic reflexes (muscarinic receptors). Sympathetic reflexes (e.g., excitement) are difficult to predict since there are opposing effects. It (i.e., norepinephrine) stimulates the acinar cells to secrete but limits secretion because it causes vasoconstriction to the salivary glands. Usually the net effect is decreased salivation with excitement or anxiety. Sypathetic stimulation (excitement) in the cat frequently results in a profuse salivation. In cats, the vasoconstriction associated with sympathetic stimulation is either transient or of insufficient magnitude to curtail secretion. Therefore, if the salivation is of sympathetic origin, atropine will not block it.