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SF4 Exam I > GI Structure and Function > Flashcards

GI Structure and Function Flashcards

1
Q

In the GI tract the vagus nerve innervates what structures?

A

esophagus
stomach
small intestine
upper colon

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2
Q

In the GI tract the pelvic nerve innervates what structures?

A

descending colon
sigmoid colon
rectum
anal canal

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3
Q

GI parasympathetic fibers synapse with what?

A

cells in enteric/intrinsic nervous system

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4
Q

GI sympathetics synapse where and what is the exception

A

outside the GI tract in pre-vertebral ganglia

some blood vessels and secretory cells are innervated directly

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5
Q

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

A

motor neurons
sensory neurons
interneurons

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6
Q

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

A

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

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7
Q

What are the two networks of the enteric nervous system

A

myenteric plexus

submucosal plexus

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8
Q

The enteric nervous system innervates what?

A

blood vessels
smooth muscle
secretory cells
endocrine cells

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9
Q

The enteric nervous system maintains what?

A

integrity of barrier between gut lumen and cells within gut wall

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10
Q

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

A

extrinsic system

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11
Q

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

A

found throughout GI tract

mostly controls motility

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12
Q

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

A

found predominantly in intestines

mostly controls secretion

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13
Q

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

A

True

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14
Q

Extrinsic Nervous System dominates control in what area

A

esophagus
stomach
defecation

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15
Q

Enteric Nervous System dominates control in what areas

A

small intestine

large intestine

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16
Q

What are the types of gastrointestinal peptides

A

hormones
paracrines
neurocrines

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17
Q

What are the GI hormones (name them all)

A 
Gastrin
Cholecystokinin (CCK)
Secretin
Glucose-dependent Insulinotropic Peptide (GIP)
Motilin
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18
Q

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

A

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)

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19
Q

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

A

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

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20
Q

Vagal Stimulation of Gastrin is mediated by what

A

Gastrin Releasing Peptide (GRP)

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21
Q

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

A

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

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22
Q

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

A

because cholecystokinin (CCK) is secreted and inhibits gastric emptying

23
Q

The signal for satiety is controlled by what hormone

A

cholecystokinin (CCK)

24
Q

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

A

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
Q

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

A

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
Q

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

A

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

27
Q

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

A

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
Q

Name the GI Paracrines

A

somatostatin

histamine

29
Q

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

A

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
Q

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

A

secreted by enterochromaffin-like (ECL) cells

increases gastric acid secretion both directly and by potentiating effects of gastrin and ACh

31
Q

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

A

around the acid-secreting portion of stomach

32
Q

What are the GI Neurocrines

A

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

33
Q

Vasoactive Intestinal Peptide (VIP)

A

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
Q

what is thought to mediate pancreatic cholera/ watery diarrhea syndrome

A

Vasoactive Intestinal Peptide (VIP)

35
Q

Gastrin-Releasing Peptide (GRP)

A

released from nerves in gastric mucosa by vagal stimulation

stimulates gastrin release

36
Q

Enkephalins

A

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
Q

Why are opiates useful in treating diarrhea

A

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

38
Q

Slow waves are initiated by?

A

interstitial cells of Cajal

39
Q

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

A

via gap junctions

40
Q

what are slow waves of GI smooth muscle

A

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

41
Q

What are the phases of slow waves

A

depolarization phase
plateau phase
repolarization phase

42
Q

depolarization phase of slow waves is caused by what?

A

Ca2+ influx

43
Q

plateau phase of slow waves is caused by what?

A

Ca2+ influx

44
Q

repolarization phase of slow waves is caused by what?

A

K+ efflux

45
Q

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

A

plateau phase must exceed threshold

46
Q

action potentials being initiated in the GI tract do what?

A

increase strength and duration of contraction

47
Q

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

A

not required

almost always present

48
Q

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

A

required everywhere except for stomach for contraction to occur

49
Q

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

A

very little influence on slow waves

greatly influence action potentials

50
Q

neural or hormonal input can influence variations in membranes how?

A

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

51
Q

frequency of slow waves does what?

A

sets maximum frequency for contraction of given part of GI tract

52
Q

Pancreatic Cholera/Watery Diarrhea Syndrome are mediated by what?

A

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

53
Q

Gastrinoma

A

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

54
Q

Steatorrhea

A

fat in feces

SF4 Exam I (16 decks)

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