Goal 1: Gastro Intro Flashcards
Steps of what happens when you eat a meal?
- Distention of GI tract wall—stretch receptors activated—sensory input sent to CNS—-CNS increases parasymp to increase motility—-goes to pancreas to tell it to release insulin
- GI lumen senses carbs—-tells endocrine cells of small intestine—-GLP-1 and GIP activated—-goes to pancreas to tell it to release insulin
- nutrients digested and absorbed—-plasma amino acids and glucose increase—- pancreas releases insulin
What’s Amylin for? How is it similar to Incretins?
- released from pancreatic beta cells
- DOES NOT CAUSE INSULIN SECRETION
- does other stuff to prevent big sugar spikes after a meal like slow gastric emptying
What are the two Incretins? What do they do? What organ releases them?
- GLP 1
- GIP
- stimulate insulin secretion after eating
- from pancreatic beta cells of Islets of Langerhans
What do Ghrelin and Leptin do? What are their different pathways?
-Ghrelin: hunger hormone made by gastric mucosal cells, increases appetite just before meals
Fasting—-Ghrelin released—-hypothalamus told—-stimulates orexiogenic and inhibits anorexiogenic—-appetite increases
-Leptin: made by adipose cells, decrease appetite to decrease fast stores
During meal—Leptin released—-hypothalamus told—-stimulate anorexiogenic and inhibit orexiogenic—decrease appetite and increases energy losing
Leptin ve Ghrelin: ways of how they are adversaries?
- gastric bypass: lost Ghrelin activity so that’s why bypass is so effective since Leptin may be inhibiting it
- in obesity: thought that Leptin is inhibited by ghrelin
What are all the GI hormones?
- Gastrin
- Cholecystokinin
- Secretin
- Motilin
- Gastric Inhibitory Peptide
- Glucagon-Like Peptide-1
What stimulates Gastrin to be released? What cells does it come from? What does it do? What inhibits it?
- peptides and amino acids
- G Cells
- stimulates gastric acid secretion and mucosal growth
- Somatostatin inhibits it
What stimulates Cholecystokinin to be released? What cell is it released from? What is it’s target organs? What does it do?
- fatty acids
- I Cells
- gallbladder, pancreas, stomach
- stimulate gallbladder contraction and pancreatic enzyme secretion, inhibits gastric emptying, promotes satiety
What stimulates the release of Secretin? What cells do they come from? What organs do they target? What do they do?
- acid in small intestines
- S Cells
- pancreas and stomach
- stimulates HCO3 secretion, inhibits gastric emptying
What stimulates Motilin to be released? How often is it released? What cells do they come from? What organs are their target? What do they do? What inhibits it?
- fasting
- every 1.5-2hrs
- endo M Cells
- gastric and intestinal smooth muscle
- stimulates migrating motor complex
- eating a meal inhibits it
What stimulates GIP release? What cells do they come from? What organ is their target? What do they do?
- glucose, FA, and amino acids in small intestine
- K cells
- target beta cells of pancreas
- stimulates INSULIN release, inhibits gastric emptying
What stimulates GLP-1 release? What cells do they come from? What organ is their target? What do they do?
- mixed meals with carbohydrates or fats
- from L Cells
- endocrine pancreas is the target
- STIMULATES INSULIN RELEASE and INHIBITS GLUCAGON RELEASE, inhibits gastric emptying, promotes the feeling of fullness
What’s the difference between short and long reflexes of the GI system?
- short: stimulus sensed by GI tract receptors and that’s processed ALL INSIDE THE ENTERIC NS
- long: signals sent to CNS from receptors INSIDE OR OUTSIDE the GI tract
What are the steps of the Relaxation Pathway within the GI tract?
- stimulus: sight, smell, thought of food, food in GI tract
- sensory receptors: inside (eg chemoreceptors) or outside (eg photoreceptors) GI tract
- input signal: AP sent via afferent neurons
- integrating center: sent to CNS or enteric nervous system
- output signal: AP sent via efferent neurons (para or sym or enteric)
- target: effector cells of GI tract target exocrine or endocrine muscle cells
- response: change secretion and motility of GI tract
What neurotransmitters contract smooth muscles?
- Ach
- Enkephalins
- Substance P
What neurotransmitters relax smooth muscles?
- Norepinephrine
- Vasoactive Intestinal Peptide (VIP)
- nitric oxide (NO)
- Neuropeptide Y
What neurotransmitters increase salivary secretion?
- Ach
- Norepinephrine
- Substance P
What neurotransmitters decrease intestinal secretion?
- Enkephalins (opiates)
- Neuropeptide Y
What neurotransmitters increase pancreatic secretion?
- Ach
- VIP
What neurotransmitters increase gastric secretion?
- Gastric-Releasing Peptide (GRP) aka Bombesin
- Ach
Which neurotransmitter comes from cholinergic neurons? Adrenergic neurons? Vagal neurons?
- cholinergic: Ach
- adrenergic: norepinephrine
- Vagal: GRP
What neurotransmitter relax sphincters? Which contracts?
- relax: Ach
- contract: norepinephrine
What activates Myosin light chain kinase (MLCK)?
Ca2-Camodulin
What are the 5 steps of smooth muscle contraction and relaxation?
- 1: intracellular Ca2 increase when Ca2 enters cell and is released from SR
- 2: Ca2 binds to calmodulin
- 3: now Ca2-calmodulin activated MLCK
- 4: MLCK phosphorylates light chain myosin heads and increase myosin ATPase activity
- 5: active myosin cross bridges slide along actin and create muscle tension
What causes the spikes in Spike Potentials?
-Ca ions enter fibers and cause CONTRACTION
What 3 things cause depolarization (spikes) in Spike Potentials?
- stretch
- Ach
- parasympathetics
What two things stimulate hyperpolarization (relaxation) Spike Potentials?
- norepinephrine
- sympathetics
What causes Slow Waves? How does it happen? What type of junctions do slow waves go through?
- Intersitial cells of Cajal
- back to back depolarizations (influx of Ca) and repolarizations (efflux of K)
- gap junctions
What two ions control the resting membrane potential of the GI smooth muscle?
- Ca: depolarization
- k: repolarization
What are the two types of contractions? What areas of the body does it happen?
- Tonic: constant contraction or tone without relaxation—upper region of stomach; in lower esophageal, ileocecal, and internal anal sphincter
- physic: periodic contractions followed by relaxation—esophagus, gastric antrum, small intestines
What will happen if no constant contraction to LES?
- Heartburn
- stomach acid contents will back up without that tightness at that sphincter keeping it down
What happens if tonic contractions don’t happen at the ileocecal sphincter?
-stool backs up into the ileum, bacteria increases so does the chance of infection
What are the two ways to categorize smooth muscles?
- Communication: single unit and multi unit
- contraction: tonic and phasic
What is the difference between single unit and multiunit smooth muscle cells? Where do you see them?
- single: connected by gap junctions, contract individually—walls of most hollow organs like bile duct, ureters, uterus, blood vessels
- multi: no gap junctions, and each cell must be stimulated independently—iris and ciliary body of eye, piloerector muscles
Describe the structure of a smooth muscle cell.
- non-striated
- dense bodies with actin attached to it
- regulated by myosin-thick filament regulated
- spindle shaped
- Side polar cross bridge arrangement
- no troponin complex
What are the 4 layers of GI tract? What are in each?
- mucosa: layer of epithelial cells, lamina propria, Muscularis mucosae
- Submucosa: submucosal plexus
- Muscularis externa: longitudinal layer of smooth muscles, myenteric plexus, circular layer of smooth muscles
- serosa
What type of cells do the myenteric plexus have?
Interstitial cells of Cajal
Where are Peyer’s Patches located? What does it contain and what are their function?
- small intestine mucosa
- have lymphoid follicles
- helps with immune system
What are the functions for the liver? The pancreas?
- liver: glucose and fat metabolism, protein synthesis, bile production, hormone production, urea production, detoxification, storage
- pancreas: exocrine-make digestive enzymes, endocrine-make hormones like insulin
