Gastric Motility Flashcards
Is GI muscle single or multi-unit smooth muscle?
[single unit – visceral muscle has
gap junctions that couples the cells and act as a single unit
explain the latch bridge mechanism in smooth muscle to reduce ATP
The latch bridge mechanism is a physiological mechanism that allows smooth muscle to maintain a sustained contraction with minimal energy expenditure. In skeletal muscle, ATP hydrolysis is required to maintain muscle contraction, but in smooth muscle, the latch bridge mechanism allows for a long-lasting contraction without requiring continuous ATP hydrolysis.
In smooth muscle, contraction is initiated by the binding of calcium ions to calmodulin, which activates the enzyme myosin light chain kinase (MLCK). MLCK phosphorylates the myosin light chain (MLC), which causes the myosin heads to bind to actin filaments and initiate contraction. During contraction, ATP is required to break the actomyosin cross-bridges and allow the muscle to relax.
However, in the latch bridge mechanism, a different protein called myosin phosphatase is activated. Myosin phosphatase dephosphorylates the MLC, causing the myosin heads to remain bound to actin even in the absence of calcium ions. This maintains the muscle contraction without requiring continuous ATP hydrolysis.
The latch bridge mechanism is thought to be important in maintaining sustained contractions in smooth muscle in various tissues, such as the uterus during childbirth, the digestive tract during peristalsis, and blood vessels in the control of blood pressure.
Are actin and myosin arrangements highly structured in smooth muscle?
no, not arranged in highly organised rows like in skeletal muscle
Which cells act as pacemakers in the GI tract?
Interstitial cells of Cajal
Electrical pacemaker activity: ICCs generate spontaneous electrical pacemaker activity, which is the basis for the contractions of smooth muscles in the GI tract. They act as a “pacemaker” for the GI tract, initiating the electrical signals that stimulate muscle contractions.
Transmit signals: ICCs transmit these electrical signals to the smooth muscles of the GI tract via gap junctions, which are small channels that allow for direct communication between cells. This signal transmission leads to the contraction of smooth muscle cells, which propels food and waste materials through the digestive tract.
Modulate activity: ICCs can also modulate the activity of smooth muscles by releasing neurotransmitters, such as acetylcholine and nitric oxide, which can either stimulate or inhibit muscle contractions.
What is the term used to describe smooth muscle when it is able to function over a wide range of lengths?
The term used to describe smooth muscle when it is able to function over a wide range of lengths is “plasticity”. Smooth muscle cells are able to stretch and contract without losing their ability to contract and generate force, which allows them to function effectively over a wide range of lengths. This is in contrast to skeletal muscle, which has a limited range of motion and loses its ability to generate force if it is stretched beyond a certain point. The plasticity of smooth muscle is important in many biological processes, including the regulation of blood flow, digestion, and reproductive function
what effects does Vagal stimulation have on gastric mobility
Increase gastric mobility.
Increased gastric motility: Vagal stimulation can increase the contractions of the smooth muscles in the stomach, which can increase the rate of gastric emptying and the movement of food through the digestive tract.
Increased secretion of gastric juice: Vagal stimulation can also increase the secretion of gastric juice, which is necessary for the breakdown of food in the stomach. This can improve digestion and nutrient absorption.
Relaxation of the pyloric sphincter: The pyloric sphincter is a ring of smooth muscle at the bottom of the stomach that controls the release of food into the small intestine. Vagal stimulation can cause the pyloric sphincter to relax, allowing food to pass more easily from the stomach into the small intestine.
What effects does CCK have on gastric mobility
Decreases
Decreased gastric motility: CCK can decrease the contractions of the smooth muscles in the stomach, which can slow down the rate of gastric emptying and the movement of food through the digestive tract.
Increased secretion of digestive enzymes: CCK can stimulate the secretion of digestive enzymes from the pancreas and bile from the gallbladder, which are necessary for the breakdown of food in the small intestine.
Increased sensation of fullness: CCK can also increase the sensation of fullness, which can reduce the amount of food a person eats and help regulate their appetite.
What effect does GIP have on GIT mobility
inhibits the basal and stimulated secretion of acid by the stomach, the secretion of pepsin, the release of gastrin, and the motility of the stomach.
What effect does secretin have on gastric mobility
Inhibits gastric acid secretion: Secretin can inhibit the secretion of gastric acid from the stomach, which can help prevent damage to the lining of the small intestine.
Increases bile secretion: Secretin can stimulate the secretion of bile from the liver and gallbladder, which aids in the digestion and absorption of fats in the small intestine.
Decreases mobility
Which has the fastest rate of spontaneous activity: stomach, duodenum, ileum or
colon?
Duodenum - 13 contractions per min
Which is involved in peristalsis: circular or longitudinal smooth muscle?
Both
