Intro to GI physiology

Question 1

sympathetic innervation of GI that is different from parasympathetic

Answer 1

sympathetic can synapse on myenteric plexus or directly on motor neurons that innervate muscle or on secretory neurons that secrete

Question 2

vago-vagal reflex tract

Answer 2

vagus sensory afferents in digestive track (nodose ganglion) send info to nucleus of tractus solitaries (NTS) synapses here then sends efferents through vagus nerve back to digestive tract

Question 3

paracrine signaling includes what molecules and what cells release them

Answer 3

somatostatin and histamine

enteroendocrine cells

Question 4

somatostatin:
secreted by what cells
Stimuli
actions
where else secreted

Answer 4

• D cells of GI mucosa
• stimuli: decreased pH in the lumen
• actions: decrease gastric H+ secretion and inhibits secretion of other GI hormones
• Secreted in hypothalamus and delta cells of exocrine pancreas

Question 5

Histamine is secreted by what cells

Answer 5

enterochromaffin-like cells in gastric glands (ECL)

Question 6

target and action of histamine

Answer 6

parietal cells to secrete acid production

Question 7

how do hormones get to specific receptor

Answer 7

• enteroendocrine cells have secretary granules filled with hormone peptides that are released upon stimulation
• secreted into portal circulation, pass through liver, and go to systemic circulation
• bind to specific receptors on target cell

Question 8

criteria to be a hormone

Answer 8

1) substance must be secreted in response to physiologic stimulus and carried in bloodstream to distant site
2) function must be independent of neural activity
3) must have been isolated, purified, chemically identified, and synthesized

Question 9

Gastrin:
site of secretion
Stimuli of secretion

Answer 9

• G cells of the antrum of stomach

- small peptides and aa, distension of the stomach, vagal stimulation via GRP

Question 10

CCK
site of secretion
stimuli of secretion

Answer 10

site is I cells of duodenum and jejunum

small peptides and aa, fatty acids

Question 11

secretin:
site of secretion
stimuli of secretion

Answer 11

S cells of duodenum

fatty acids in duodenum, and H+ in duodenum

Question 12

Glucose-dependent insulinotropic peptide

Answer 12

duodenum and jejunum

oral glucose, aa, fatty acids

Question 13

Gastrin actions

Answer 13

parietal cells secretion of gastric acid

stimulates growth of gastric mucosa

Question 14

Zollinger-Ellison syndrome

Answer 14

increase gastrin and H+ from parietal cells

• hypertrophy of gastric mucosa
• duodenal ulcers
• steatorrhea

Question 15

steatorrhea

Answer 15

from gastrin-secreting tumors: increased H+ secretion results in acidification of intestinal lumen, so pancreatic lipase inactive so fat not absorbed so its excreted in stool

Question 16

CCK actions

Answer 16

HCO3- pancreatic bicarb secretion potentiation (w/secretin)
Exocrine pancreas and gallbladder growth
Pancreatic enzyme secretion
Inhibits gastric emptying
contraction of gallbladder and relaxation of sphincter of oddi

Question 17

Secretin actions

Answer 17

pancreatic and biliary HCO3- secretion
decrease gastric H+ secretion
inhibits trophic effect of gastrin on gastric mucosa

Question 18

GIP is secreted by what cells?

Answer 18

K cells of duodenal and jejunal mucosa in response to FA,aa,glucose

Question 19

GIP actions

Answer 19

• increase insulin secretion from pancreatic B cells

- decrease gastric H+ secretion

Question 20

vasoactive intestinal peptide source

Answer 20

neurons of mucosa and SM

Question 21

gastrin releasing peptide source

Answer 21

neurons from gastric mucosa

Question 22

enkephalins source

Answer 22

neurons of mucosa and SM

Question 23

NPY source

Answer 23

neurons of mucosa and SM

Question 24

substance P source

Answer 24

Co-release with ACh

Question 25

Ach action

Answer 25

- contraction of SM - relaxation of sphincters - increased salivary secretion - increased gastric secretion - increased pancreatic secretion

Question 26

Norepinephrine actions

Answer 26

relaxation of SM contraction of sphincters increased salivary secretion

Question 27

VIP action

Answer 27

relaxation of SM increased intestinal secretion increased pancreatic secretion

Question 28

Gastrin-releasing peptide (GRP) action

Answer 28

increased gastrin secretion

Question 29

enkephalins actions

Answer 29

- contraction of SM | - increased intestinal secretion

Question 30

NPY actions

Answer 30

relaxation of SM | increased intestinal secretion

Question 31

substance P action

Answer 31

conctraction of SM | increased salivary secretion

Question 32

satiety center is located in which nucleus?

Answer 32

ventromedial nucleus

Question 33

feeding center is located where?

Answer 33

lateral nucleus

Question 34

integrative center btwn feeding and satiety

Answer 34

arcuate nucleus

Question 35

a-melanocortin (a-MSH) pathway

Answer 35

- a-MSH released by POMC neurons - a-MSH binds to MCR-4 present in second order neurons - inhibits food intake and increases metabolism (anorexigenic)

Question 36

neuropeptide y pathway

Answer 36

hunger stimulates release NPY NPY binds Y1R neurons that release NPY also release AGRP which antagonizes MCR-4 = increase feeding behavior and storage of calories (orexigenic)

Question 37

cases of obesity have been related to mutations in the ___ and ___ genes

Answer 37

POMC and MCR-4

Question 38

ghrelin

Answer 38

secreted by endocrine cells in stomach binds to growth hormone secretagogue receptors in hyoothalamus it stimulates neurons that release NPY

Question 39

other actions of ghrelin

Answer 39

increases appetite, gastric motility, gastric acid secretion, adipogenesis

Question 40

insulin binds

Answer 40

to receptors in satiety and hunger centers within hypothalamus

Question 41

insulin inhibits and stimulates

Answer 41

inhibits NPY | stimulates POMC

Question 42

insulin actions

Answer 42

decrease appetite and increase metabolism

Question 43

CCK elicits ___ | decreases what and increases what

Answer 43

``` satiety acts on vagal-->NTS-->hypothalamus circuit -decreases ghrelin decreases gastric emptying increases gastric distension ```

Question 44

PYY binds

Answer 44

Y2 receptors of hypothalamus and inhibits NPY, releases inhib of POMC potential as appetite suppressor

Question 45

Leptin is secreted by what cells

Answer 45

adipose tissue and by endocrine cells in stomach

Question 46

leptin binds to what

Answer 46

POMC and NPY, stimulates POMC inhibits NPY

Question 47

leptin increase and decrease

Answer 47

increase metab | decrease ghrelin and appetite