Renal and GI physio Flashcards
Pepsinogen
Source, Stimulus, Action
Source: Chief cells
Stimulus:
- Stretch, Ach from vagus nerve
- HCl
Action: precursor for pepsin (10-20% of protein digestion)
Somatostatin
Source, Stimulus, Action
Source: D cells
Stimulus: Low gastric pH (food has moved on from stomach so no longer providing buffer so pH in stomach drops).
Action:
- paracrine: Inhibit gastrin secretion
- endocrine: inhibit pariatal cell acid secretion
- neurocrine: Decrease gastric motility
Phases of Gastric Secretion
- Cephalic - 30%
- sight/smell of food
- ach from vagus nerve
- gastrin from G cells
- histamine from ECL cells - Gastric - 60%
- Gastric digestion and release of peptides
- stretch - vasovagal and local enteric reflexes
- gastrin from G cells - Intestinal - 10% - shuts down gastric secretion
- gastric emptying
- decreases intestinal and gastric antral pH
- somatostatin from D cells
- Secretin from S cells
- CCK from I cells
What is the purpose of the oxyntic glands and where are they located?
What cells are found here?
Exocrine - Acid secretion
Located in body/fundus of stomach
Parietal cells, chief cells, mucus neck cells
What is the purpose of the pyloric glands and where are they located?
What cells are found here?
Endocrine - Secrete gastrin
Located in the atrum of the stomach
G cells
Gastrin
Source, Stimulus, Action
Source: G cell
Stimulus:
- stretch and vagal stimulation
- peptides and amino acids (spec. phenylalanine and tryptophan)
Action:
- acts on enterochromaffin-like cells in an endocrine like fashion to tell them to secrete histamine which acts on parietal cells
- acts on parietal cells to secrete stomach acid
What is the most potent stimulator of parietal cells?
Histamine
What are the three receptors on parietal cells? What binds to them and how do they activate the parietal cells?
M3 (ach), H2 (histamine), CCK (gastrin)
M3 and CCK increase intracellular calcium and histamine increases cyclic AMP to result in activation of parietal cells by a shape change to secrete HCl.
What is an example of a somatostatin anologue and what does it do?
Ocrtreotide
- inhibit acid secretion and gastrin release
Ghrelin
Source, Stimulus, Action
Source: Stomach (intestine, pancreas, hypothalamus)
Activation: GOAT
Action:
- Pituitary GH secretion
- Stimulate appetite, growth, fat deposition
- Anti-inflammatory
MOA of entyce
Ghrelin analog
Transient increases in growth hormone and IGF-1
Leptin
Source, Stimulus, Action
Source: Adipocytes
Stimulus: Increased fat tissue
Action:
- decrease production of appetite stimulators in hypothalamus (neuropeptide Y, Agouti related protein)
- Activation of POMC neurons ( alpha melanocyte stimulating hormone, activation of melanocortin receptors
- increase sympathetic activity - increase activity and metabolic rate
- decrease insulin secretion
- Pro-inflammatory
Secretin
Source, Stimulus, Action
Source: S cells in duodenum
Stimulus: low duodenal pH (acid), lipids
Action:
- Inhibit acid secretion from parietal cells
- Slow gastric emptying
- Secretion of bicarb rich pancreatic fluid
Cholecystokinin (CCK)
Source, Stimulus, Action:
Source: I cells of duodenum and jejunum
Stimulus: Amino acids (also FA’s, acid)
Actions:
1. Pancreas
- potentiates secretin
- pancreatic enzyme secretion
2. Gallbladder
- gallbladder contraction
- Relaxation of sphincter of Oddi
3. Inhibition of gastric liquid emptying
What are the exocrine cells of the pancreas? Endocrine?
Acinar (digestive enzymes) and ductal cells (bicarb rich fluid)
Alpha (glucagon) and beta cells (insulin)
What stimulates the acinar cells to secrete zymogens?
CCK, Ach
What stimulates the ductal cells?
Secretin
What is an incretin? Give 2 examples.
Hormones from intestine secreted in response to nutrients that potentiate insulin secretion
- GIP
- GLP1
How much conjugated bile acid is reabsorbed in terminal ilium?
95%
Gastric Inhibitory Peptide
Source, Stimulus, Action
Source: K cells of intestine
Stimulus: intraduodenal FA and AA»_space; carbohydrates
Action:
- Inhibit gastric acid secretion
- Stimulate insuline secretion during hyperglycemia
What is the incretin effect?
Oral glucose will cause a much larger spike in insulin than IV glucose
Glucagon like peptide 1 (GLP1)
Source, Action, Stimulus
Source: L cells of ileum and colon (widespread in cats)
Stimulus: intraluminal glucose and lipids
Action:
- inhibit gastric acid secretion
- stimulate insulin secretion
- inhibit gastric emptying (ileal break)
Peptide YY
Other name, Source, Action, Stimulus
AKA GLP-2
Source: Distal ileum and Colon
Stimulus: FAs, less so carbs
Actions:
- Ileal break (slows gastric emptying)
- inhibit CCK and secretin secretion
- proliferation of gut mucosa
What is the gastrocolic reflex?
Distension of the stomach results in activation of colon leading to defecation
