GI Structure and Function Flashcards Preview

SF4 Exam I > GI Structure and Function > Flashcards

Flashcards in GI Structure and Function Deck (54):
1

In the GI tract the vagus nerve innervates what structures?

esophagus
stomach
small intestine
upper colon

2

In the GI tract the pelvic nerve innervates what structures?

descending colon
sigmoid colon
rectum
anal canal

3

GI parasympathetic fibers synapse with what?

cells in enteric/intrinsic nervous system

4

GI sympathetics synapse where and what is the exception

outside the GI tract in pre-vertebral ganglia
some blood vessels and secretory cells are innervated directly

5

The enteric (intrinsic) nervous systemis made up of what types of neurons?

motor neurons
sensory neurons
interneurons

6

Vagovagal reflex (where is the information coming from and going to and through what nerves)

vagus nerve afferents relay info from mucosa and smooth muscle to CNS
vagus nerve efferents carry response back to GI tract

7

What are the two networks of the enteric nervous system

myenteric plexus
submucosal plexus

8

The enteric nervous system innervates what?

blood vessels
smooth muscle
secretory cells
endocrine cells

9

The enteric nervous system maintains what?

integrity of barrier between gut lumen and cells within gut wall

10

How does the enteric nervous system relay information to and from the gut (via what pathway)

extrinsic system

11

myenteric plexus (where is it found and what does it do)

found throughout GI tract
mostly controls motility

12

submucosal plexus (what does it do and where is it found)

found predominantly in intestines
mostly controls secretion

13

True/False: Stimulus in one part of GI tract can produce response in another part in absence
of extrinsic nervous system

True

14

Extrinsic Nervous System dominates control in what area

esophagus
stomach
defecation

15

Enteric Nervous System dominates control in what areas

small intestine
large intestine

16

What are the types of gastrointestinal peptides

hormones
paracrines
neurocrines

17

What are the GI hormones (name them all)

Gastrin
Cholecystokinin (CCK)
Secretin
Glucose-dependent Insulinotropic Peptide (GIP)
Motilin

18

Zollinger-Ellison Syndrome (what is it and what are the symptoms)

hypersecretion of gastric acid due to continuous release of gastrin into blood from gastrinoma in small intestine or pancreas
develop duodenal ulcers, diarrhea, and steatorrhea (excess fat in stool)

19

Gastrin (where is it secreted, in response to what, and what does it stimulate)

secreted from G cells in stomach (antrum)
released in response to peptides and amino acids from protein digestion, distention of stomach, vagal stimulation
stimulates HCl secretion by parietal cells

20

Vagal Stimulation of Gastrin is mediated by what

Gastrin Releasing Peptide (GRP)

21

Cholecystokinin (CCK) (where is it secreted, in response to what, and what does it do)

secreted from I cells of proximal small intestine (duodenum and jejunum)
released in response to small peptides, amino acids, fatty acids, and monoglycerides (w/ 8 or more Cs)
stimulates gallbaldder contraction and pancreatic enzyme secretion
potentiates pancreatic bicarbonate secretion stimulated by secretin
inhibits gastric emptying
signal for satiety

22

What is the reason fatty meals empty more slowly than non-fatty meals

because cholecystokinin (CCK) is secreted and inhibits gastric emptying

23

The signal for satiety is controlled by what hormone

cholecystokinin (CCK)

24

Secretin (where is it secreted, in response to what, and what does it do)

release by S cells of proximal small intestine (duodenum)
released in response to acid
stimulates bicarbonate and water secretion in pancreas and liver
increase bile production
inhibits gastric acid section by parietal cells

25

Glucose-Dependent Insulinotropic Peptide (GIP) (where is it secreted, in response to what, and what does it do)

secreted by K cells in proximal small intestine (duodenum and jejunum)
released in response to fatty acids, glucose, and amino acids (to a lesser extent)
stimulates insulin release from pancreas

26

Why is oral glucose load more effective than intravenous glucose in causing insulin release

because of glucose-dependent insulinotropic peptide (GIP) stimulating insulin release from pancreas in response to glucose

27

Motilin (where is it secreted, in response to what, and what does it do)

released cyclically every 90 minutes from upper small intestine during fasting (duodenum and jejunum)
stimulates migrating myoelectric complex in stomach and small intestine
release abolished by eating

28

Name the GI Paracrines

somatostatin
histamine

29

Somatostatin (where is it secreted, in response to what, and what does it do)

secreted by D cells throughout the GI tract (mucosa)
released in response to acid
inhibits gastric acid secretion and release of gastrin
inhibits release of all GI hormones

30

Histamine (where is it secreted, in response to what, and what does it do)

secreted by enterochromaffin-like (ECL) cells
increases gastric acid secretion both directly and by potentiating effects of gastrin and ACh

31

where are enterochromaffin-like (ECL) cells found in high concentrations

around the acid-secreting portion of stomach

32

What are the GI Neurocrines

vasoactive intestinal peptide (VIP)
gastrin-releasing peptide (GRP or bombesin)
enkephalins

33

Vasoactive Intestinal Peptide (VIP)

released from nerves in mucosa and smooth muscle of GI tract
predominant action- relaxation of GI smooth muscle
stimulates intestinal and pancreatic secretion
secreted from pancreatic islet cell tumor

34

what is thought to mediate pancreatic cholera/ watery diarrhea syndrome

Vasoactive Intestinal Peptide (VIP)

35

Gastrin-Releasing Peptide (GRP)

released from nerves in gastric mucosa by vagal stimulation
stimulates gastrin release

36

Enkephalins

secreted from nerves in mucosa and smooth muscle of GI tract
stimulate contraction of GI smooth muscle (particularly the lower esophageal, pyloric, and ileocecal sphincters)
inhibit intestinal secretion of fluid and electrolytes

37

Why are opiates useful in treating diarrhea

enkephalins (from the opiates) inhibit intestinal secretion of fluid and electrolytes

38

Slow waves are initiated by?

interstitial cells of Cajal

39

Slow waves are spread from interstitial cells of Cajal to other cells how?

via gap junctions

40

what are slow waves of GI smooth muscle

period changes in resting membrane potential of smooth muscle
potential rhythmically depolarizes and repolarizes
also called basic electrical rhythm (BER)

41

What are the phases of slow waves

depolarization phase
plateau phase
repolarization phase

42

depolarization phase of slow waves is caused by what?

Ca2+ influx

43

plateau phase of slow waves is caused by what?

Ca2+ influx

44

repolarization phase of slow waves is caused by what?

K+ efflux

45

for slow wave contraction to occur what most happen (in regards to plateau phase)

plateau phase must exceed threshold

46

action potentials being initiated in the GI tract do what?

increase strength and duration of contraction

47

action potentials in stomach contractions (required/not required and present/not present)

not required
almost always present

48

Action potentials in GI tract (requried/not required and where) for contraction

required everywhere except for stomach for contraction to occur

49

neural or hormonal input on slow waves and action potentials of GI tract

very little influence on slow waves
greatly influence action potentials

50

neural or hormonal input can influence variations in membranes how?

produce action potentials and thus contractions
can inhibit action potentials
determine strength of contractions

51

frequency of slow waves does what?

sets maximum frequency for contraction of given part of GI tract

52

Pancreatic Cholera/Watery Diarrhea Syndrome are mediated by what?

vasoactive intestinal peptide (VIP) b/c it stimulates intestinal and pancreatic secretion

53

Gastrinoma

small tumor in the small intestine (duodenum) or pancreas that produces high levels of gastrin

54

Steatorrhea

fat in feces