Physiology Flashcards
What are the Interstitial cells of Cajal? What is their role?
The are intrinsic pacemaker cells near the myenteric plexus. They are connected themselves and to smooth muscle, generating rhythmic slow wave membrane potentials to alter its excitability
What is the vaso vagal reflex? give example.
When local stimuli e.g. stretch activate vagal afferents, go to dorsal vagal complex, vagal effects cause acid secretion, swallowing etc.
What is the cephalic phase of digestion? What nerve regulated? What # of gastric acid secreted here?
Triggered by anticipation of food.
Causes salivation and 30% of gastric acid secretion, also pepsin secretion.
Corpus and fundas also relax
Regulated by vagus nerve
What 3 cell types does the vagus nerve stimulate in the stomach? (2 in corpus and 1 in antrum) What is the result?
What does it inhibit?
Stimulates parietal cells and ECL-cell in corpus and G cells in antrum. Result is acid secretion from parietal cells.
Inhibits D cells in corpus and antrum
What activates D cells? What do they produce and what does that do?
Acid in antrum/duodenum and gastrin.
Produce somatostatin which inhibits parietal cells and ECL-cells
What happens when acid hits the duodenum? How is the vago-vagal reflex involved?
- D cells activated to produce somatostatin
- Vaso-vagal reflex causes Brunner’s glands to be activated secreting mucus and bicarbonate.
- The reflex also inhibits gastric emptying
- Duodenum-pyloro-antral reflex also causes the pylorus to close
What secretes cholecystokinin? (CCK) what does it do? What causes its secretion?
I cells in the small intestine.
It causes the gall bladder to contract, the SOO to relax, suppresses the appetite via the hypothalamus.
Amino acids and fatty acids arriving in duodenum
What causes secretin release? What cells release it? What does it do?
Amino acids and low pH in the duodenum.
S cells release it.
It causes the secretion of the bicarbonate rich solution from the pancreas and neutralising the acid.
What 3 motor patterns are occuring in the duodenum?
- Retropulsion
- Segmentation
- Peristalsis
Where are the two amylases from and what do they do?
One in saliva and one from pancreas.
They break down starch into disaccarides maltose and maltotriose.
What enyzmes are present on the brush border?
What do they produce?
Maltase and sucrase which are secreted as one glycoprotein and broken there by pancreatic enzymes.
Break maltose, maltotriose and sucrose into glucose.
Isomaltase also there assisting
Where and how is glucose absorbed in the SI?
With Na via SGLT1 (sodium-dependent glucose transporter)
What enzyme in the stomach and SI gets protein digestion going?
Pepsin in stomach.
In SI endopeptidases do, trypsin being one which when activated activates the others. (all come inactive from pancreas)
What is the main enzyme that breaks down fat?
What helps it do that?
How is the fat absorbed?
What system carries it away?
Pancreatic lipase.
Helped by bile which capture and make smaller droplets (micelles)
Absorbed as fatty acid and monoglycerol.
Remade into triglycerol in epithelial, packages into cholymicrons and goes into lymphatics
What is the main variable between people that effects metabolic rate/energy expenditure?
Level of physical activity
