Lecture 22: Neuroendocrine Control Flashcards
What is the intrinsic nervous system
Enteric nervous system
ENS samples gut content through ___
Receptors
Efferent ENS neurons innervate what
Smooth muscle, secretory and absorptive cells
Macronutrients are sensed by receptors expressed in enteroendocrine cells. Enteroendocrine cells possess ___ extending into the gut lumen coming into direct contact with macronutrients
Microvilli
Afferent neurons of the ENS are ___neurons
Cholinergic
Afferent nervousness innervate ___ and ___
Mucosa and muscle
Efferent excitatory neurons release what
ACh, Substance P
What do excitatory neurons do to longitudinal/sphincter smooth muscle and secretions
Contract longitudinal/sphincter smooth muscle and stimulate secretions
What do inhibitory neurons secrete
NO, VIP, and ATP
What do inhibitory neurons do to smooth muscle cells, secretion and do they vasodilate or constrict
Inhibit smooth muscle cells, stimulate secretions, and cause vasodilation
What does the myenteric plexus innervate
Longitudinal and circular muscle
What is the myenteric plexus in control of
Gut movements
What does the submucosal plexus innervate
Glandular epithelium, intestinal endocrine cells, and submucosal blood vessels
What is the submucosal plexus in control of
Intestinal secretions
___help to integrate extrinsic and intrinsic input and communicate between myenteric and submucosal plexus
Interneurons
Enteric interneurons establish ___patterns by inhibiting effector neurons in alternating segments
Segmentation
What is ileus
Hypomotility or amotility of GI tract in absence of obstruction
What are the 3 categories of mechanisms that can cause ileus
- Neurogenic
- Inflammatory
- Pharmacological
What do opioids do to GI motility and how
Bind u2 receptors in myenteric plexus causing hypomotility
What is the extrinsic NS
Autonomic- SNS and PNS
Who as the dominant control over the enteric NS the PNS or SNS
PNS
What is the main function of the PNS in the ENS
Promote digestion
What is the main function of the SNS in ENS
Inhibit digestion and recover fluid volume
ENS can operate without input from CNS in ___animals and why
Monogastric, can’t in ruminants because poor fermentation
Describe the pathway and feedback of low pH stimulating bicarbonate release
- Low pH in duodenum
- S cells in duodenum secrete secretin
- Target organ: pancreas
- Bicarbonate release
What do G cells release and where are they located
Release gastrin
Located in the pyloric antrum and duodenum
What is the release stimuli for gastrin
Anticipation of food, stomach distention, presence of proteins/peptides in stomach
What inhibits gastrin release
HCl, somatostatin, secretin and GIP
Gastrin stimulates ___pump activity of __ cells
H/K ATPase pump activity of parietal cells
Gastrin stimulates the release of ___ from ECL cells
Histamine
Histamine stimulates ___mediated insertion of H/K ATPase pumps into parietal cells
CAMP
What do D cells secrete and where are they located
Secrete somatostain and are located in the stomach, pancreas and hypothalamus
What is the release stimuli for somatostatins
Low pH, CCK
What is direct function of somatostatin
Inhibiting AC of parietal cells and antagonize stimulatory effect of histamine
What is the indirect effect of somatostatin
Inhibiting G cells, ECL cells, and parietal cells
Somatostatin is blocked by ___ stimulation during ___ and ___ phase
Vagal, cephalic and gastric
During __phase somatostatin release is stimulated by low __ ins to ACh and by __
Intestinal phase, pH, and CCK
Somatostatin inhibits ___secretion
Gastric acid
Somatostatin inhibits ___ and ___ cells
G cells and E cells
What do S cells secrete and where are they located
Secretin in the crypts of Lieberkuhn in duodenum
What is the release stimuli for secretin
Entry of fat and acid into duodenum
What is the function of secretin
- PH regulation by promoting bicarbonate release
- Reduce gastrin secretions by blocking G cells
What do I cells secrete and where are they located
Secrete CCK and are located in duodenal and jejunal mucosa and neurons in ileum and colon
What is the release stimuli for CCK
Presence of fatty acids, amino acids, and peptides in chyme entering duodenum
What inhibits CCK
Somatostatin
What is the function of CCK
- Enzyme secretion from pancreas
- Contraction of gallbladder to release bile
- Activation of D cells- somatostatin
What do K cells secrete and where are they located
Gastric inhibitory peptide (GIP) in the duodenal and jejunal mucosa
What is the release stimuli for GIP
Presence of glucose and fatty acids in chyme entering duodenum
T or F: glucose injected into blood will increase GIP activity
False only glucose in small intestines increase GIP
What is the function of GIP
- Inhibit parietal cells
- Increase insulin release
What do M cells secrete and where are they located
Motilin located in duodenal and jejunal mucosa
What is the release stimulus for motilin
Increasing pH in duodenum
What is the function of molitin
- Increase gastric emptying during interdigestive migrating motility complex, MMC
- Increase somatostatin release from pancnreas
Erythromycin is a __receptor agonist
Motilin
What is erythromycin use for
Enhance gastric emptying and intra-digestive migratory motor complex
What acts on the salivary glands during cephalic phase
PNS stimulation of Acinar and ductal cells
What happens to gastric secretions during cephalic phase
- PNS stimulation- ENS via ACh stimulates G cells and parietal cells
- G cells secrete gastrin in blood
- Gastrin finds CCK on parietal and chief cells
What are the pancreatic secretions like during cephalic phase
ENS via ACh stimulates Acinar and ductal cells
What happens to salivary glands during gastric phase
PNS stimulation
What happens to gastric secretions/motility during gastric phase
- Stomach is distended which stimulates stretch receptors
- Information transmitted through afferent fibers. G cells stimulated (more gastrin) and parietal cells stimulated (more HCl)
- Low pH lumen is perceived by G cells and activates somatostatin
- Histamine is produced by ECL cells and triggers HCl via H2 receptors
What are the pancreatic secretions during the gastric phase
ENS stimulates ductal and Acinar cells
What are the salivary glands doing during intestinal phase
Ceasing activity
What are the gastric secretions and motility like during intestinal phase
- Duodenal distention, fat, protein trigger release of CCK which cause stomach to relax
- CCK stimulates D cells releasing somatostatin
What happens to pancreatic cells during intestinal phase
ENS via ACh stimulates Acinar and ductal cells.
CCK activates Acinar cells
Secretin activates ductal cells
During the intestinal phase gastric secretions ___
Decrease
What is the neural and humoral control during intestinal phase
Neural: removal stimuli
Humoral: somatostatin released and inhibits parietal and ECL cells
Somatostatin ___intracellular cAMP levels
Decreases
What is Gastrinoma/Zollinger-Ellison Syndrome
Rare neuroendocrine tumor that is constantly secreting gastrin, uninhibited by somatostatin.
Stimulates release of gastric acid
What are the results of gastrinoma
Parietal cell mass, acid secretion—> peptic ulcer
Decrease bile acids and lipase activity lead to diarrhea, steatorrhea, and hypokalemia
What are some treatment options for gastrinoma
- Blocking H/K pump to heal ulcers
- Somatostatin to suppresses gastrin
- Surgical resection of tumor
