Lecture 4.A. - Pancreatic Secretions Flashcards
_____ cells in the pancreas secrete digestive enzymes directly into pancreatic ducts (Exocrine function). The duct cells secrete _____. These contents travel into the _____ to facilitate digestion and protection from stomach acid, respectively.
Acinar cells
Bicarb
Duodenum
Unlike Lipases and Proteases, ______ are secreted in active forms from the pancreas.
As a secondary means of protecting against auto-digestion, the pancreas produces _____ inhibitors, which prevent its premature activation.
Amylases
Trypsin inhibitors
Pancreatic aqueous secretions are just about always _____ (hypo-, hyper-, or isotonic?) with plasma. How does this work?
Isotonic
Na+ and K+ secretions are held constant at isotonic concentrations, but HCO3- increases with a mirrored decrease in Cl- –> maintains isotonicity.
_____ is the hormone that stimulates extralobular secretion of Bicarb by pancreatic duct cells. Unlike intralobular cells, extralobular cells do NOT secrete _____ into the ducts.
Secretin
Cl-
While Pancreatic duct cells and Parietal cells in the stomach both use Carbonic anhydrase to form HCO3- intracellularly, how do they differ in its transport?
Pancreatic duct cells have HCO3-/Cl- exchanger on LUMEN side with H+/Na+ exchanger on BASOLATERAL side.
Parietal cells are just the opposite.
_____ is responsible for secreting/recycling Cl- back into the lumen of the pancreatic duct after its exchange with HCO3- –> this buildup of negatively charged ions allows ___ and ___ to diffuse into the lumen via the Paracellular mech.
What should follow as these ions diffuse into the lumen?
CFTR
Na+ and K+
Water will follow via aquaporin.
____ cells in the duodenum respond to increasing HCl concentration and fatty acids by secreting Secretin –> stimulates _____ secretion from Duct cells and Acinar cells in pancreas –> Pancreatic _____ concentration DECREASES via dilution as a result of this process.
S-cells
HCO3-
Amylase
Like in the stomach, ____ from the Vagus nerve acts via the _____ receptor to stimulate enzyme secretion from Pancreatic Acinar cells.
____ from I-cells in the duodenum has a similar but LESSER effect via the ____ receptor.
ACh
M3
CCK
CCK-1 aka CCK-alpha (remember that gastrin binds CCK-2 aka CCK-beta.)
_____ and _____ potentiate the effects of CCK and ACh on pancreatic Acinar cells via the second messenger _____.
_____ acts to inhibit Adenylyl cyclase –> decreases ____ –> inhibits effects of CCK and ACh.
VIP and Secretin
cAMP
SST
cAMP
Epithelial cells in the duodenum recognize Amino acids and Fatty acids when food is consumed –> duodenal epithelial cells secrete _____-__ –> in combination with _____ peptide secreted from neural stimulation of Pancrease in response to thoughts of food, they bind to I-cells in the duodenum to stimulate secretion of ____ into the blood –> travels to pancrease and acts on Acinar cells.
CCK-RP (CCK releasing peptide)
Monitor peptide
CCK
As peptide concentration from food decreases throughout digestion, there is more ____ (which enzyme?) available in the duodenum –> acts on CCK-RP and Monitor peptide –> ______ (increases or decreases?) CCK secretion.
Trypsin
Decreases
Keep in mind CCK has both Neural and Endocrine pathways. Neuronally, it is released from the basolateral side of I-cells in the duodenum and acts directly on the ____ nerve –> stimulates its action on the pancreas. It also activates an _____-_______ reflex –> directly stimulates enzyme secretion from pancreatic Acinar cells.
Vagus (afferent)
Entero-pancreatic reflex
Why does neural stimulation of Pancreatic Acinar cells have greater effect than Hormonal?
There are few CCK-1 receptors in the Pancreas but many ACh receptors.
While vagal stimulation ____ (increases or decreases?) blood flow and vasodilation of the Pancreas, stimulation of the ______ nerve does just the OPPOSITE.
Increases
Splanchnic
