GI Flashcards
What nervous system uses ACh?
Enteric and Parasympathetic
What are the functions of ACh?
increases motility (contraction of smooth muscle),
increases secretion
relaxation of sphincters
What nervous system uses Substance P?
Enteric and Para
What are the functions of Substance P?
increase motility
acts on NK-1 Receptor to promote salivary secretion
What are the actions of Nitric Oxide and what Nervous System uses it?
Para and ENS
muscle relaxation by inhibition of smooth muscle
Actions of Norepinephrine and used by what nervous system?
Sympathetic
decrease motility, blood flow, secretion
increase sphincter tone
Actions of Neuropeptide Y and used by what nervous system
Symp and ENS
decreases motility and secretion
What are the actions of Vasoactive Intestinal Polypeptide and what Nervous System uses it?
Enteric
muscle relaxation, increase secretions
acts on salivary glands to increase salivation and blood flow
What are the actions of Opiods (Met & Leu enkephalins) and what Nervous System uses it?
decreases motility and secretion
What are the actions of Serotonin(5-HT) and what Nervous System uses it?
ENS
initiate a local peristaltic reflex in sensory intrinsic neurons
transmit a discomfort signal in extrinsic sensory nervs
What are the actions of GABA and what Nervous System uses it?
ENS
Inhibits motility and secretion
What type of cells secrete Gastrin and where are theses cells located?
G cells
antrum of stomach
What stimulates the release of Gastrin
- small peptides and amino acids
- distention of stomach
- vagal stimulation
What inhibits Gastrin?
decrease in pH
somatostatin
What are the actions of Gastrin?
- stimulates H+ secretion of parietal cells
2. stimulates growth of the gastric mucosa (trophic effect)
What type of cells secrete CCK and where are theses cells located?
I cells
Duodenum, jejunum
What stimulates the release of CCK?
monoglycerides & fatty acids, small peptides, a.a
What are the 3 actions of CCK?
- contraction of the gallbladder with simultaneous relaxation of the sphincter of oddi
- increase pancreatic lipases
- along with Secretin acts to slow down gastric emptying and increase secretion of bicarbonate from the pancreas
What do Pancreatic lipases digest
lipids to fatty acids, monoglycerides, cholesterol
Pancreatic amylase digest_____?
carbohydrates
Pancreatic proteases digest ______?
protein
CCK is a part of what family and why?
gastrin- CCK family
C-terminal pentapentide is identical
CCKa receptor is most selective to what hormone and why?
CCK
sulfating of tyrosine residue on CCK makes it selective for receptor
CCKb receptor is selective to what hormone?
CCK and gastrin equally
What type of receptors are CCKa and b?
G-coupled Receptors
What type of cells and where is secretin produced?
S cells of the duodenum
What stimulates secretin?
H+
fatty acids
(secreted when acid contents arrive in the duodenum
What are the actions of Secretin?
increase pancreatic and biliary bicarbonate to neutralize H+
allow for pancreatic lipases to become activated(need pH of 6-8)
inhibits the effects of gastrin on parietal cells ( acts as an enterogastrone)
What type of cells and where is Glucose Dependent Insulinotropic Peptide produced?
K cells of the duodenum and jejunum
What Stimulates GIP?
Fatty acids and carbohydrates
What are the actions of GIP?
stimulates insulin secretion and decreases H+
Why is oral glucose more effective at increasing insulin than IV glucose?
oral glucose stimulates GIP and Beta cells in pancreas while IV glucose only stimulates Beta cells
When is Motilin secreted?
fasting state
What action does motilin have?
increases motility during the fasting state
What are the 5 paracrines in the GI?
- Somatostatin
- Histamine
- Prostaglandins
- Serotonin (5-HT)
- Adenosine
What type of cells secrete somatostatin?
D cells in the pancreas and hypothalamus
what are the actions of somatostatin?
decreases luminal pH
inhibits gastic H+ secretion
Histamine is secreted by ____.
endocrine type cells in the H+ secreting region of the the stomach
What are the actions of Histamine?
stimulates H+ secretion by the Parietal cells
What are the actions of prostaglandins?
stimulates bicarbonate secretion to help protect the gastric barrier
what are the actions of adenosine?
causes vasodilation
modulation of motility reflexes and colonic chloride secretion
Ptyalin is produced what salivary gland and what cells?
P, SM acinar
Lingual Lipase is produced by____?
SL acinar cells
Kallikrein is produced by ___?
P,SM, SL acinar cells
What neurotransmitters regulate salivary secretion?
Para: ACh –> M3 (blocked by atropine)
Substance P –> NK-1
Symp: Beta and Alpha receptors
what neurotransmitters stimulate blood flow?
para: ACh and VIP
increases in salivation itself directly dilates the bld vessels , more kallirein is secreted
In the peristaltic reflex which neurotransmitters cause muscle contraction?
Ach and Substance P
In the peristaltic reflex which neurotransmitters cause muscle relaxation?
NO and VIP
Muscle tone of the LES and distal esophagus is determined by what?
Myogenic Activity
What happens to muscle tone with bilateral vagotomy?
LES tone may not be altered since excitatory and inhibitory influences are removed in equal amount
What happens to LES muscle tone if atropine is taken?
selective removal of only excitatory influence can lead to relaxation due to NO/VIP input dominating.
What is dysphagia?
difficulty swallowing
What is achalasia?
idiopathic destruction of parasympathetic ganglia of myenteric plexus –> failure of LEX to relax, impaired peristalsis in distal esophagus
Two major factors that slow or inhibit gastric emptying?
- Fat: mediated by CCK which is secreted when fatty acids arrive in the duodenum. CCK slows gastric emptying
- H+: ENS via myenteric plexus ensures that the gastric contents delivered to duodenum are neutralized
Migrating motor complex is mediated by _____?
Motilin
Food entering the stomach requires what two things?
receptive relaxation and accommodation
what is accommodation?
increase in volume without increasing in pressure
What increases stomach peristalsis?
carbs distension gastrin motilin ACh
What decreases stomach perstalsis/ slows emptying?
Fat Over distention GIP, VIP, CCK Peptide YY GLP-1 & 2 NE
What speeds stomach emptying at the pylorus?
Gastrin
ACh
What slows stomach emptying at the pylorus?
Secretin
CCK
NE
Pancreatic Secretion has what two components?
The primary secretion by the acinar cells secrete an isotonic flood which is the enzymatic component
The aqueous component is provided by the ductal secretion.
Pancreatic enzymes are stored in zymogen granules at the apical end. By what process and what neurotransmitters will stimulate their release?
Exocytosis by activation of cAMP through secretin –> SCTR, VIP–>VPAC2 or Ca2+ pathway through ACh –>M3, GRP, CCK –>CCKa
Define the osmolarity of pancreatic juice?
isotonic
During what phase is pancreatic secretion initiated?
cephalic phase
During what phase is most pancreatic secretion released?
intestinal phase
Pancreatic secretion during the intestinal phase is mediated by what nervous system?
ENS
enteropancreatic reflex involving ACh, CCK and VIP
What is the difference in stimuli for CCK and secretin?
CCK is released in response to free FA, other paracrine enterocytes that release CCK-releasing peptide, and monitor peptide from acinar cells.
Secretin is released by S cells sensing the pH in the lumen.