Green - GI Tract: Structure And Function

Question 1

Reflex found in GI tract in which afferent and efferent impulses travel via the vagus nerve

Answer 1

Vagovagal reflex

Question 2

Fat in feces

Answer 2

Steatorrhea

Question 3

Small tumor in the small intestine or pancreas that produces high levels of gastrin

Answer 3

Gastrinoma

Question 4

Cells in GI tract that release histamine

Answer 4

Enterochromaffin-like cells

Question 5

Intrinsic nervous system of GI tract that is separate from the CNS

Answer 5

Enteric nervous system

Question 6

In extrinsic nervous system, the vagus nerve innervates:

Parasympathetic innervation

Answer 6

Esophagus, stomach, small intestine and upper colon

Question 7

In extrinsic nervous system, pelvic nerve innervates (parasympathetic innervation)

Answer 7

Descending colon
Sigmoid colon
Rectum
Anal canal

Question 8

The _______ plexus and ________ plexus form networks of the enteric nervous system

Answer 8

Myenteric

Submucosal

Question 9

The enteric nervous system innervates:

Answer 9

Blood vessels, smooth muscle, secretory cells, and endocrine cells

Question 10

The enteric nervous system relays info to and from the gut via

Answer 10

The extrinsic system

Question 11

Myenteric plexus is found thru/o GI tract and mostly controls

Answer 11

Motility

Question 12

The submucosal plexus is found predominantly in the intestines and mostly controls

Answer 12

Secretion

Question 13

Extrinsic control of muscles dominates in

Answer 13

Esophagus

Stomach

Defecation

Question 14

Enteric control of muscles dominates in

Answer 14

Small intestine

Large intestine

Question 15

3 different subtypes of gastrointestinal peptides

Answer 15

Hormones

Paracrines

Neurocrines

Question 16

Gastrin is secreted from ?

Answer 16

G cells in stomach

Question 17

Gastrin is released in response to ?

Answer 17

Peptides and amino acids from protein degradation

Distention of stomach

Vagal stimulation

Question 18

Gastrin acts to ?

Answer 18

Stiimulate HCl secretion by parietal cells of stomach

Question 19

Patients with ______ hypersecrete gastric acid due
to continuous release of gastrin into blood from gastrinoma in small intestine
or pancreas; they develop duodenal ulcers, diarrhea, and steatorrhea (excess fat in stools)

Answer 19

Zollinger-Ellison Syndrome

Question 20

Cholecystokinin is secreted from ?

Answer 20

I cells of the proximal small intestine

Question 21

Cholecystokinin is released from I cells in the proximal small intestine in response to ?

Answer 21

small peptides, AA’s, fatty acids, monoglycerides (containing 8 or more carbons) that bind to I cells

CCK releasing peptide

Monitor peptide

Question 22

Monitor peptide is released from the ?

Answer 22

Pancreas

Question 23

CCK-releasing peptide is secreted by ?

Answer 23

Paracrine cells w/in epithelium into lumen of small intestine

Question 24

In the absence of a meal, what happens to both CCK releasing peptide (from paracrine cells) and monitor peptide (from pancreas)

Answer 24

They are both degraded by trypsin

Question 25

Functions of cholecystokinin (CCK)

Answer 25

stimulates gallbladder contraction and pancreatic enzyme secretion;
potentiates pancreatic bicarbonate secretion stimulated by secretin inhibits gastric emptying – reason fatty meals empty more slowly than non- fat meals
signal for satiety

Question 26

Explain what secretin does

Answer 26

Secretin is released by S cells in the proximal small intestine in response to acid. It stimulates the pancreas and liver to release bicarbonate and water, which both neutralizes the acid and decreases acid production in parietal cells. It also increases bile production

Question 27

Explain glucose dependent insulinotropic peptide (GIP)

Answer 27

GIP is secreted in the proximal small intestine by K cells as a response to glucose and fatty acids (and a lesser extent amino acids) it stimulates the release of insulin from the pancreas.

Question 28

Explain motilin

Answer 28

Motilin is released cyclically every 90 minutes from the upper small intestine and stimulates a migrating myoelectric complex in the stomach and small intestine. Release of motilin is abolished by eating.

Question 29

Explain the paracrine factor somatostatin

Answer 29

Secreted by D cells throughout the entire small intestine in response to acid in the lumen. Somatostatin inhibits the release of all GI hormones. It also inhibits gastric acid secretion and the release of gastrin

Question 30

Explain the GI role of Histamine:

Answer 30

Histamine is secreted in the acid producing portions of the stomach by enterochromaffin-like cells. It causes increased gastric acid secretion both directly and by potentiating the effects of gastrin and ACh.

Question 31

Explain vasoactive intestinal peptides actions (VIP

Answer 31

VIP is release from nerves in the mucosa and intestinal smooth muscle. It’s main action is to cause smooth muscle relaxation. It also stimulates intestinal and pancreatic secretion.

Question 32

Explain how Gastrin-Releasing peptide works

Answer 32

GRP (bombesin) is released from nerves in the gastric mucosa secondary to vagal stimulation. GRP then causes the release of gastrin.

Question 33

Explain the actions of enkephalins

Answer 33

Enkephalins are released from the gastric mucosa and the smooth muscle of the GI tract. They cause the contraction of GI smooth muscle, especially the lower esophageal, pyloric, and iliocecal sphincters. Enkephalins also inhibit the secretion of fluid and electrolytes (stopping diarrhea)

Question 34

GI smooth muscle slow waves are generated by ?

Answer 34

Interstitial cells of Cajal

Question 35

Are slow waves action potentials?

Answer 35

No

Question 36

Periodic changes in resting membrane potential of smooth muscle cells.

Potential rhythmicity depolarizes and polarizes

Also called basic electrical rhythm

Characteristic of GI smooth muscle

Answer 36

Slow waves