Physio

Question 1

What are the 4 GI peptide hormones?

Answer 1

gastrin, secretin, CCK, glucose-dependent-inhibitory peptide (GIP)

Question 2

Gastrin

Answer 2

• secreted by G cells of tummy (antrum)
• stomach distention/vagal stimulation via GRP (gastrin releasing peptide) cause secretion
• increase gastric H+ secretion (directly on parietal cell for HCl and indirectly ECL cell for HA)
• peptide hormone

Question 3

cholecystokinin

Answer 3

• secreted by I cells of duodenum/jejunum
• secreted in response to fats
• increase gallbladder contraction, pancreatic enzyme/bicarbonate secretion
• decreases gastric emptying
• peptide hormone

Question 4

secretin

Answer 4

• secreted by S cells of duodenum
• secreted when chyme leaves tummy
• increases bicarb/pancreatic fluid sectretion
• inhibits gastrin (therefore, stops acidic secretions), stops gastric emptying
• peptide hormone

Question 5

glucose-dependent insulinomic peptide (GIP)

Answer 5

• secreted by K cells of duodenum/jejunum
• secreted in response to fat/carbs
• stimulates insulin secretion from pancreas
• inhibits HCl secretion by parietal cells
• peptide hormone

Question 6

What does VIP do?

Answer 6

• neurocrine of mucosa/smooth muscle
• relaxes smooth muscle
• increases intestinal secretions
• increases pancreatic secretions

Question 7

What are the GI paracrines?

Answer 7

somatostatin, serotonin, histamine

Question 8

serotonin

Answer 8

• enterochromaffic cells of intestine

- respond to distension by exciting ENS to increase motility and secretions

Question 9

somatostatin

Answer 9

• D cells of tummy produce it
• inhibits pancreatic and gastric secretions, motility
• can be endocrine or paracrine

Question 10

histamine

Answer 10

• released by EC-like cells in tummy

- stimulates HCL secretion (H2 receptors)

Question 11

mucus neck cells, cardiac glands (these only near esophagus)

Answer 11

• secrete mainly mucus

- in antrum of tummy

Question 12

peptic (chief) cells

Answer 12

• secrete pepsinogen (cleaved to pepsin at low pH) and gastric lipase
• in body of tummy

Question 13

parietal (oxyntic, acid-forming) cells

Answer 13

• secrete intrinsic factor (cyanocobalamin reab. in ileum) and HCl
• in body of tummy

Question 14

HCO3-/Cl- exchanger (no energy!!)

Answer 14

bicarb from carbonic anhydrase sent to blood, Cl- enters from blood

Question 15

H+/K+ ATPase

Answer 15

H+ from carbonic anhydrase into tummy lumen (digestion), K+ into cell

Question 16

What does prolonged vomiting cause?

Answer 16

hypokalemia (kidney response), alkalosis (lost HCl), dehydration (lost volume/H2O)

Question 17

What stimulates acid secretion?

Answer 17

histamine, vagus, gastrin, caffeine, insulin, stress

Question 18

What inhibits acid secretion?

Answer 18

somatostatin, GIP (gastric inhibitory peptide), secretin, glucose insulinotropic peptide

Question 19

Whom does the vagus stimulate?

Answer 19

• parietal cells, ECL cells, D cells (directly via ACh)
• G cells (via GRP)
• D cells (inhibits somatostatin via ACh)

Question 20

What’s in saliva normally?

Answer 20

• hypotonic (less osmolarity than plasma)
• alpha-amylase, lingual lipase
• high K+, high bicarb
• low Na+, low Cl-
• uses Cl-/bicarb, K+/H+, Na+/H+ transporters

Question 21

What about high flow rates?

Answer 21

• less time for ion reabsorption
• bicarb higher, K+ low
• saliva more like plasma

Question 22

What about low flow rates?

Answer 22

• more time for ion reabsorption
• less Na+/Cl-
• more K+, lower bicarb

Question 23

What’s in pancreatic secretions?

Answer 23

• lots of bicarb to neutralize acidic chyme (CCK/secretion increase bicarb secretion)
• isotonic secretion