Lecture 10 - Properties of GI Smooth Muscle Flashcards
In contrast to other excitable tissue, the Resting Membrane Potential of GI smooth muscle Oscillates. These oscillations are called ____ ____ rhythm (slow waves), and are initiated by interstitial cells of _____ in the muscle layer.
Basic Electrical Rhythm (slow waves)
Cajal
With GI smooth muscle, the threshold for ______ is less than the ______ threshold. How does Slow wave crossing of each of these thresholds dictate contraction of smooth muscle?
Contraction
Electrical
Slow waves crossing threshold for contraction will induce smaller contraction than Slow waves crossing both the threshold for contraction and electrical threshold.
How does the frequency of Slow waves, and thus the frequency of Contraction, compare between the Stomach, Small intestine, and Colon?
Small intestine has HIGHEST frequency, then the Stomach, then the Colon.
Keep in mind the frequency decreases moving from the proximal Small intestine to the colon.
Keep in mind that GI smooth muscle contraction is induced by _____ influx into smooth muscle cells. Thus, a common side effect of _____ channel blockers like Diltiazam and Nifedipine is stomach cramps
Ca++ influx
Ca++ channel
ACh and Substance ___ (Parasympathetic stimulation) bring the resting membrane potential ______ (closer or further?) to the electrical potential. Thus, Sympathetic stimulation via NE, ____, and NO will cause the opposite.
Substance P
Closer
VIP
Note that the contractility of the GI tract is completely different between meals. Rather than following the Basic Electrical Rhythm (Slow wave), it is regulated by Migrating _____-_______ complex. This is a contractile wave propagated from the ____ and travelling to the _____. It is thought to be a way to clear the GI of remnants after a meal –> _____, a hormone from the duodenum, is a major factor regulating this process.
Migrating Myo-electric Complex
Stomach
Ileum
Motilin
