GI phys Lecture 2

Question 1

Difference between segmentation and Peristalsis

Answer 1

Peristalsis: involves smooth muscle / longitudinal muscle interaction, moving contents forward. Propulsion.

Segmentation: purpose is to mix contents. Promotes digestion

Question 2

Secretion:

Acinar Cells / Duct cells

Answer 2

Acinar cells connected to duct cells, both are polarized. (transporters are different from apical and basolateral).

Acinar cells: synthesize / secrete pdts.

Duct cells: transport fluid / electrolytes

Question 3

Increase of flow rate, what happens?

Answer 3

Na increases, plateaus
HCO3- (bicarbonate) increases, plateaus
Cl- increases, linear
K+ decreases, plateus

Question 4

Sjogren Syndrome

Answer 4

Difficulty in tasting/chewing/swallowing/speaking

Dry mucosa, parotid glands enlarged. Autoimmune disorder

Question 5

LES and cardia, what is there

Answer 5

Mucus and Bicarbonate.

Bicarbonate there to maintain pH bc u don’t want acid in esophagus

Question 6

Fundus and upper body secretions

Answer 6

H+, intrinsic factor, mucus, bicarbonate, pepsinogen and lipase

has parietal cells that secrete HCl

Question 7

Antrum and lower body contain…

Answer 7

Mucus and bicarbonate

Question 8

Tubulovesicles

Answer 8

Contain H+, K+ ATPase, morphological change occurs, making canaliculus have more surface area from resting to secreting. In parietal cells.

Question 9

Apical (lumen) transporters of Parietal cells

Answer 9

H / K exchanger
K and Cl can leave through channels

Does not secrete HCl directly, secretes H+ ions and Cl-

Question 10

Basolateral transporters of Parietal cells

Answer 10

HCO3- / Cl-
Na / K
CO2 can come from blood / plasma

Question 11

Which receptors are stimulatory and inhibitory for parietal cells? Which are the secondary messengers associated with these?

Answer 11

Basolateral receptors of ACh, gastrin, histamine stimulate parietal cells, secreting HCl.

M3 = ACh
H2 = Histamine
CCK-B = Gastrin

ECL cell make histamine

Somatostatin (SST) from D cells is ALWAYS inhibitory.

Ca++ for ACh and Gastrin, cAMP for Histamine are the secondary messengers

Question 12

Mechanism of G cells in Antrum

Answer 12

GRP (gastrin releasing peptide) stimulates G cells which makes Gastrin which stimulates parietal secretion of HCl.

D cells stimulate SST which inhibit G cell production of Gastrin.

Note that Gastrin is not a NT (it is a GI hormone) and must be transported via blood.

Question 13

PPI (proton pump inhibitor) mechanism

Answer 13

Inhibits final step, H+ K+ ATPase in parietal cells.

Question 14

Effects of H. Pylori and how it affects gastric mucosa:

skip

Answer 14

Increase NH3 production
Decrease number antral D cells
Increase prod. of gastrin
Increase acid secretion
Inflammatory responses release cytokines

Question 15

Effects of NSAIDS and how it damages gastric mucosa
skip

Answer 15

Less mucous and bicarbonate production, increase gastrin secretion, decrease gastric blood flow, neutrophils release free radicals and proteases.

NSAIDS inhibit prostaglandins, u need prostaglandins for healthy gastric mucosa.

Question 16

3 agents that stimulate pancreatic secretion

Answer 16

CCK, secretin, ACh.

Vagal nerve fibers responsible for ACh.

Question 17

Difference between CCK and Secretin

Answer 17

CCK primary affect on acinar cells, Secretin primarily duct cells.

Secretin causes production of bicarbonate as a buffer, cholecystokinin promotes synthesis of enzymes.

Both are GI hormones and thus must be transported by blood.

Question 18

Acute / Chronic Pancreatitis facts

skip

Answer 18

Gallstones / alcohol consumption cause this. Gallstones can cause fluid from pancreas to back up. Fluid containing enzymes can start digesting the pancreas.

Question 19

How to have constriction behind of a bolus:

How to have relaxation on other side of bolus:

Answer 19

Propulsive segment: Circular muscle contracts, longitudinal muscle relaxes. Inhibitory motor neurons are off

Receiving segment: Relaxation of circular muscle, contraction of longitudinal. Inhibitory motor neurons are on.

Question 20

Gastro colic reflux

Answer 20

Connection between motility pattern in the colon and what goes on in the stomach

Mass movement / Segmentation can occur after you eat a meal.