Gi Physiology

Front 1

What is the difference between hormones, paracrines, and neurocrines?

Back 1

They all regulate GI function but hormones are delivered in blood, paracrines diffuse through interstitial fluid, and neurocrines are released from neurons.

Front 2

What are 5 GI tract hormones?

Back 2

Gastrin, Cholecyctokinin, Secretin, GIP, motilin

Front 3

What are the two important paracrine agents?

Back 3

Somatostatin and histamine

Front 4

What are three peptide neurocrines?

Back 4

VIP, bombesin (GRP) and enkephalins

Front 5

What is the division of parasympathetic control on the GI system?

Back 5

From esophagus to transverse colon, parasympathetic supply by vagus nerve. From transverse colon to anal canal, parasympathetics supply by pelvic nerves.

Front 6

What is striated muscle of upper third esophagus and external anal canal innervated by? parasympathetics

Back 6

Cholinergic innervation from vagus and pelvic nerves. (parasympathetics)

Front 7

Where are cell bodies of parasympathetic nerves loccated for GI?

Back 7

Preganglionics- medulla (vagus) and spinal cord (sacral), postganglions- myenteric plexus.

Front 8

What is a vasovagal reflex?

Back 8

vagus nerve afferents deliver information to brain and relay information back to vagus nerve.

Front 9

Where are cell bodies for GI sympathetics? What is released by sympathetics?

Back 9

Preganglionics- spinal cord
Postganglionics- prevertebral ganglia (celiac, superior and inferior mesenteric, hypogastic) Preganglionics- ACh, Postganglionics- NE

Front 10

Do sympathetics and parasympathetics innervating gut include afferents?

Back 10

Yes
75% para, 50% sym

Front 11

What is the intrinsic innervation of the gut?

Back 11

Enteric nervous system made up of submucosal and myenteric plexus...relay information along the gut.

Front 12

What are neurocrine mediators of the enteric nervous system?

Back 12

Ach, NO, VIP, enkaphalins, serotonin, Sub P (a single neuron may release more than one mediator)

Front 13

What are GI hormones?

Back 13

All peptides. Can be endocrine(blood), paracrines(interstitial), neurocrine(nerves)

Front 14

Criteria to define GI hormone

Back 14

1) Response area separate from stimulus area
2) response persists when nerves are servered
3) Extract mucosa of stimulus site produces response
4) substance isolated, purified, identified, synthesized

Front 15

What are the effects of Gastrin? Where is it released from? When is it released?

Back 15

Stimulates Gastric acid secretion. Released from G cells of antral mucosa (and duodenum). When protein digestion products enter stromach, stomach is distended, or PNS (vagal stimulation).

Front 16

What triggers CCK release? What releases it? What is its action?

Back 16

Fatty meals trigger release of CCK from I cells in duodenum and jejunum. Stimulates gallbladder contraction, pancreatic enzyme secretion, bicarbonate secretion, growth of pancrease, and inhibits gastric emptying (fatty meal takes longer to digest because it spends more time in stomach)

Front 17

What causes release of secretin? where is it released from? what does it do?

Back 17

Acid in duodenum causes release of secretin which stimulates pancreatic bicarbonate secretion, bilarly bicarbonate secretion, growth of pancrease, and pepsin secretion and inhibits gastric acid secretion and trophic effets of gastrin.

Front 18

When is GIP released? From where? what does it do?

Back 18

Released by Duodenum and jejunum in response to Glucose, AA and Fatty acids (food), Stimulates Insulin release and inhibits gastric acid secretion. (Slow down...food is coming,, and prepare...insulin)

Front 19

What is role of motilin?

Back 19

Nerves fat or acid stimulates Duodenum and Jejunum, triggers gastric and intestinal motility.

Front 20

What GI hormones are released by stomach?

Back 20

Gastrin

Front 21

What GI hormones released by duodenum?

Back 21

Secretin (acid triggers bicarbonate release and inhibits more acid secretion), CCK (food triggers pancreatic enzyme release, slows gastric emptying) GIP(insulin release, less acid), Motilin (motility)

Front 22

What GI hormones released in Jejunum?

Back 22

CCK, GIP, Motilin

Front 23

What is Somatostatin? What does it do?

Back 23

A paracrine. Somatostatin acts when acid acts on GI mucosa or vagus nerve is less active. It is released from GI mucosa and pancreatic islets and inhibits gastrin release and gastric acid secretion.

Front 24

What is histamine? what does it do?

Back 24

Paracrine. released when gastrin is released from ECL cells. Stimulates Gastric acid secretion from parietal cells. Potentiates acid secretion.

Front 25

What are the neurocrines?

Back 25

VIP, Bombesin, Enkephalins

Front 26

What does VIP do?

Back 26

It is released near mucosa and smooth muscle of GI tract . It relaxes spinchters, circular muscle, stimulates intestinal and pancreatic secretion

Front 27

What does Bombesin (GRP) do?

Back 27

From Gastric mucosa stimulates gastrin release

Front 28

What do enkephalins do?

Back 28

from nerves near mucosa and smooth muscle of GI. stimulate smooth muscle contraction and inhibit intestinal secretion.

Front 29

Where and how are primary peristaltic contractions? What is their purpose?

Back 29

inititated in esophagus by swallowing. move food through esophagus.

Front 30

What initiates secondary peristaltic contractions? What is their purpose?

Back 30

initiated by distension and local reflexes. remove leftover material

Front 31

What is the principle motility function of the orad region of stomach?

Back 31

receptive relaxation mediated by vasovagal reflex allows storage.

Front 32

What is principle activity of caudal stomach?

Back 32

mixing and emptying

Front 33

What triggers gastric contractions?

Back 33

slow waves (regularly occirng depolarizations)

Front 34

Characterize small intestinal motility

Back 34

after meal: segmental and short peristaltic contractions
intermeal: brief irregular contractions and every 90 min- migrating motility complexes.

Front 35

What initiates contractions of small intestine?

Back 35

Spike potentials superimposed on slow waves.

Front 36

What are the principle movements of proximal colon?

Back 36

weak peristaltic contractions permit storage of contents and water reabsorbtion

Front 37

What is a mass movement?

Back 37

2 or 3 times a day, peristaltic wave propels material into distal colon or rectum. Distention triggers rectosphincteric reflex.

Front 38

What exhibits tonic contractions?

Back 38

all sphincters and orad stomach

Front 39

Where are there phasic contractions?

Back 39

esophagus, distal stomach (antrum), small intestine

Front 40

What effects slow waves?

Back 40

body temperature postive correlation, metabolic activity positive correlation.