10

Question 1

what are three components of gastric secretion

Answer 1

1. HCl
2. Pepsinogen - product of chief cells (concentrated in body region of body) (inactivate cleaved by HCl into active PEPSIN)
3. Mucus - mucous neck cells (protect stomach lining/neutralize acid)

Question 2

what is a zymogen

Answer 2

inactive precursors

Question 3

what does pepsin do

Answer 3

autocatalysis

break down proteins into smaller polypeptides

Question 4

Regulation of stomach motility and secretion

Answer 4

1. stimulate secretion when food is present in stomach
2. stimulate mixing when food is present
3. regulate emptying of chyme to not exceed absorptive capacity of small intestine
4. turn off secretion/motility when stomach is finished

Question 5

cephalic phase of regulation

Answer 5

stomach gets ready before food worked way down to the esophagus (smell/taste = secretion of HCl/pepsinogen)

Question 6

gastric phase of regulation

Answer 6

• the stomach has neural sensors that can detect the presence of food in the lumen and stretching of the walls. •sensors directly stimulate the SUBMUCOSAL PLEXUs They in turn synapse on the chief and parietal cells and stimulate them to secrete.
• the sensors also stimulate the release of the hormone Gastrin, which also stimulates secretion

Question 7

histamine and somatostatin are

Answer 7

paracrine regulators of parietal cells

histamine: potentiates the effects of gastrin/ACh
somatostatin: inhibits the production of acid

Question 8

direct stretching of muscle + stretch receptors = all act on sm to increase depolarisation

Answer 8

• stomach exhibits rhythmic peristaltic waves (slow waves)
• stomach has pacemaker cells near the top depolarization travels through stomach via gap junctions
• neural and hormonal stimulation act on top of the slow waves

Question 9

pyloric sphincter

Answer 9

controls the movement of material into the duodenum

Question 10

intestinal phase of regulation

Answer 10

(1) gives feedback information from the duodenum on progress of absorption/digestion. Will inhibit motility until small intestine is ready for the next batch of chyme.
(2) keeps gastric secretions at proper levels.
(3) shuts off secretion and motility when stomach is empty.

Question 11

• entry of chyme into duodenum stimulates the release of several hormones:

Answer 11

secretin
cholecystokinin (CCK)
glucose-dependent insulinotropic peptide (GIP)

Question 12

secretin

Answer 12

released in response to low pH of chyme. Inhibits gastric

secretion and motility

Question 13

cholecystokinin

Answer 13

released in response to fat (and probably protein) in chyme. Inhibits gastric secretion (and probably motility).

Question 14

glucose-dependent insulinotropic peptide

Answer 14

stimulates insulin secretion at pancreas

Question 15

Pancreatic Secretions: aqueous component

Answer 15

an alkaline fluid (full of HCO3- ), functions to neutralize stomach acids:
•pancreatic enzymes don’t work well at low pH
•stimulated by hormone secretin

Question 16

Pancreatic Secretions: digestive enzymes
•proteases (digest protein)
•lipase (digest fat)
•amylase (digest polysaccharides)
•ribo/ and deoxyribonuclease (digest RNA and DNA)

Answer 16

secretion stimulated by CCK which is released from cells in the duodenum in response to the presence of fatty acids, and protein (amino acids).

Question 17

the pancreatic proteases are also secreted in an inactive form that get activated in the small intestine

Answer 17

trypsinogen + enteropeptidase = trypsin
chymotrypsinogen + trypsin = chymotrypsin
procarboxypeptidase + trypsin = carboxypeptidase

Question 18

majority of the pancreas is

Answer 18

exocrine tissue - synthesize proteases/lipases

Question 19

endocrine tissue

Answer 19

secrete hormones

Question 20

duct cells

Answer 20

secrete bicarbonate + neutralize acid

Question 21

bile

Answer 21

•Bile is a product of the liver. Liver cells (hepatocytes) secrete bile into channels (known as bile canaliculi) that come together to form the common hepatic duct.
(alkaline salts, bile salts, lecithin(phospholipid), cholesterol, bilirubin, trace metals)

Question 22

While bile is produced in the liver, it is stored in the gall bladder.

Answer 22

• made at fairly constant rate in liver.
• passage into the duodenum is regulated by the Sphincter of Oddi.
• CCK will cause it to relax (=it opens in response to chyme in duodenum).
• between meals the Sphincter of Oddi is closed and bile backs up into the gall bladder where it gets concentrated by removal of salt and water.

Question 23

type of contraction in smooth muscle of small intestine

Answer 23

segmentation
•the rhythm of contraction is set by multiple autorhythmic cells, which send out shorter distance slow waves
•the rhythm is faster at the beginning of the small intestine = movement of chyme towards the large intestine

Question 24

what is segmentation stimulate by

Answer 24

distension of intestine
gastrin
parasympathetic nerves

Question 25

Migrating motility

Answer 25

= peristaltic contractions that act to sweep remaining material into large intestine

Question 26

The large intestine (colon)

Answer 26

* main process – active transport of Na+ out of the lumen | * water follows down it’s osmotic gradient