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GI Final > Intro to GI phys > Flashcards

Intro to GI phys Flashcards

1
Q

The main properties of the GI tract that are responsible for its role in digestion and absorption are:

A

motility and secretion

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2
Q

Name the sphincters that are found along the GI tract.

A
  1. UES
  2. LES
  3. Pylorus
  4. Sphincter of Oddi
  5. Ileocecal valve
  6. Internal anal sphintcer
  7. External anal sphincter
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3
Q

What are the functional layers of the GI tract:

A
  • mucosa layer
  • submucosa
  • muscle layers (circular muslce, longitudinal muscle)
  • Serosa
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4
Q

What makes up the enteric nervous system?

A

Submucosal plexus and myenteric plexus

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5
Q

T or F: GI function relies on central, autonomic, and enteric nervous system.

A

True

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6
Q

T or F: the enteric nervous system gets both CNS stimulation and from chemical and mechanical sensors within the wall.

A

True

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7
Q

What is meant by the extrinsic nervous system of the GI tract ?

A

ANS

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8
Q

What is meant by intrinsic nervous system of the GI tract?

A

ENS

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9
Q

Where are the cell bodies located for the extrinsic nervous system in relationship to the gut wall?

A

Outside of the gut wall

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10
Q

WHere are the cell bodies located for the intrinsic nervous system in relationship to the gut wall?

A

Located within the gut wall.

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11
Q

What nerves are involved in the parasympathetic innervation of the GI tract?

A

Vagus to esophagus, stomach, small and 2/3 of large intestine, and accessory organs like gallbladder and pancreas.
Pelvic nerves to distal 1/3 of large colon, and rectum.

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12
Q

Where are the cell bodies preganglionic nerve of the parasymapthetic located?

A

Brain (vagus) and sacral spinal cord (pelvic nerves)

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13
Q

Where are the postganglionic neurons of the PNS located?

A

THey lie within the wall of the gut wall.

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14
Q

The synpase between pre and post uses what kind of receptors and what neurotransmitter for the PNS?

A

nicotinic (nACHRs), ACh.

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15
Q

T or F, the PNS can directly innervate the GI tract

A

False. It has to go through the myenteric or submucosal plexus of the ENS.

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16
Q

T or F, the SNS can directly innervate the GI tract.

A

True.

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17
Q

For the SNS, where does the preganglionic efferent fibers arise and where do they end?

A

They arise within the spinal cord and end in the prevertebral ganglia.

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18
Q

What are the sympathetic prevertebral ganglias that innervate the GI tract?

A
  1. Celiac
  2. Superior mesenteric
  3. Inferior mesenteric
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19
Q

What type of receptors and neurotransmitters is involved in the pre and post ganglionic fibers for the PNS?

A

nACHR, uses Ach

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20
Q

What type of receptors and neurotransmitters are involved in the post and target organ for the PNS?

A

muscurinic and uses Ach.

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21
Q

For the SNS, what receptor and nt are involved in the pre and post ganglionic fibers?

A

nicotinic receptor and uses Ach

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22
Q

For the SNS, what receptor and nt are involved int he post ganglionic fibers and target organ?

A

Adrenergic (alpha or beta) and uses NE.

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23
Q

T or F, the ENS cannot exert it’s function without the CNS input

A

False.

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24
Q

What is Vagovagal reflex?

A

Refers to GI reflex circuits where afferent and efferent fibers of the vagus nerve coordinate the responses to gut stimuli via the dorsal vagal complex in the brain. It controls contraction of the GI muscle layers in response to distension of the tract by food and allows for the accomodation of large amounts of food int he GI tracts.

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25
Q

Centers that which control food intake are located where?

A

Brain

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26
Q

what is the sensory ganglion of the vagus called and where is it located?

A

Sensory ganglion of the vagal nerve is the nodose ganglion and it’s located in the nucleus of the tractus solitarius (NTS) in the brain stem.

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27
Q

Where do efferent fibers of the vagal nerve arise from?

A

NTS.

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28
Q

About what percent of the vagas fibers are afferent?

A

75%

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29
Q

Somatostatin (peptides), and histamine (messenger molecules) are examples of what kind of cellular communication?

A

paracrine regulation

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30
Q

Within the GI where is the somatostatin released from?

A

secreted by D cells of the GI mucosal enteroendocrine cells.

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31
Q

Within the GI what is the stimuli for somatostatin release?

A

decreased luminal pH

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32
Q

Within the GI, somatostain funs to what do?

A

Inhibit gastric H secretion from parietal cells. They also inhibits secretion of other GI hormones.

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33
Q

Outside of the GI tract, where is somatostatin released from?

A
  1. hypothalamus

2. delta cells of the exocrine pancreas.

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34
Q

Within the GI where is histamine stored?

A

enterochromaffin-like cells (ECL) in gastric glands.

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35
Q

Within the GI what cells secretes histamine?

A

Enterochromaffin-like cell (ECL)

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36
Q

What is the function of histamine within the GI?

A

Histamine targets parietal cells and stimulate acid production

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37
Q

After a hormone is released from the EEC in the GI tract, where does the hormone go next?

A

It goes to the portal circulation and then to the liver, then to systemic circulation and then finally to target cells.

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38
Q

What are some examples of hormones produced in the GI tract?

A
  1. gastrin
  2. CCK
  3. secretin
  4. Glucose-dependent insulinotropic peptide
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39
Q

Out of gastrin, CCK, secretin, GIP, which ones belong the same family?

A

gastrin and CCK are in the gastrin-CCK family.

GIP and Secretin are in the secretin-glucagon family.

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40
Q

What cells and where are gastrin released?

A

G cells of the pyloric antrum

41
Q

What stimuli released gastrin?

A
  • presence of small peptides and amino acids
  • distention of the stomach
  • vagal stimulation (via GRP)
42
Q

Where are CCK secreted from?

A

I cells of the duodenum and jejunum.

43
Q

What stimulates CCK release?

A

presence of small peptides and aa, and fatty acids

44
Q

Where are secretin released from?

A

S cells of the duodenum.

45
Q

What stimulates the secretion of secretin?

A

Presence of acid in the duodenum and fatty acids in duodenum.

46
Q

Where is GIP released from?

A

duodenum and jejunum.

47
Q

What stimulates GIP release?

A

Fatty acids, a.a., and oral glucose

48
Q

What is the function of gastrin?

A
  1. Gastrin increases H+ secretion from parietal cells.

2. Stimulates the growth of gastric mucosa and increase the # of parietal cells.

49
Q

What are the consequences of Zollinger-Ellison syndrome:

A

It’s a gastrin-secreting tumors which increases circulating levels of gastrin and increases acid secretion by parietal cells. The consequences are:

  1. The gastric mucosa hypertrophies.
  2. Duodenal ulcers
  3. Steatorrhea. With increased H+ will lead to duodenal ulcers. ( with increased gastrin theres more acid and acid impairs pancreatic enzymes particularly the ones responsible for digesting fat) and without the proper function of duodenum, fat is not being reabsorbed and thus will be excreted out at an abnormal level.
50
Q

In Zollinger-Ellison syndrome, you’re likely to see duodenal ulcers. Why might that be?

A

With increased levels of gastrin you’ll have increased levels of H in the mucosa which can pass on to the duodenum and destroy the lining of the duodenum.

51
Q

Explain why you’d see steatorrhea in patients with Zollinger-Ellison syndrome.

A

With increased acid in the duodenum (leading to the ulcer), the enzymes that are needed to breakdown and absorb fat are destroyed. Therefore, fat is not reabsorbed and is excreted with fece.

52
Q

What are the actions of CCK?

A
  1. increases pancreatic enzyme secretion.
  2. Increases HCO3- secretion indirectly (CCK potentiates the effects of secretin)
  3. Stimulates contraction of the gallbladder and relaxation of the sphincter of oddi
  4. stimulates growth of the exocrine pancreas and gallbladder (trophic effect leading to increased size of pancreas and gallbladder).
53
Q

What are the two types of CCK receptors?

A

CCKa and CCKb.

54
Q

Which CCK receptor is specific only for CCK?

A

CCKa

55
Q

Which CCK receptor is unspecific for CCK and secretin?

A

CCKb

56
Q

Secretin is similar to what hormone made in the pancreas?

A

glucagon.

57
Q

What are the actions of secretin?

A
  1. Increase pancreatic HCO secretion
  2. Increase biliary HCO secretion
    ( action of 1 and 2, help neutralize the acid thats coming from the stomach into the duodenum.)
  3. Inhibits trophic effect of gastrin on gastric mucosa
  4. Can also act as a paracrine signal.
58
Q

What are the actions of GIP?

A
  1. increase insulin secretion from pancreatic beta cells

2. decrease gastric H secretion

59
Q

What would be more effective in increasing insulin secretion oral of IV glucose and why?

A

Oral glucose administration, because oral glucose stimulates GIP, which stimulates insulin secretion, and has also direct stimulatory effects on beta cells.

60
Q

What are some of the neurotransmitters of the GI tract?

A
  1. Ach
  2. NE
  3. VIP (vasoactive intestinal peptide)
  4. GRP (gastrin-releasing peptide)
  5. Enkephalins
  6. Neuropeptide Y
  7. Substance P
61
Q

What is the action of ACH in the GI?

A
  1. contraction of smooth muscle
  2. relaxation of sphincters
  3. Increase salivary, gastric, and pancreatic secretion.
62
Q

What are the action of the NE?

A
  1. Relaxation of the smooth muscle
  2. Contraction of sphincters
  3. increase salivary secretion
63
Q

What are actions of VIP?

A
  1. relaxation of smooth muscle

2. increase intestinal and pancreatic secretion

64
Q

What are actions of GRP?

A

increase gastrin secretion

65
Q

What is the action of Enkephalins

A
  1. Contraction of smooth muscle

2. decrease intestinal secretion

66
Q

What is the action of neuropeptide Y

A
  1. Relaxation of smooth muscle

2. decrease intestinal secretion

67
Q

What is the Action of substance P?

A
  1. Contraction of smooth muscle

2. increase salivary secretion

68
Q

Where are neural centers that control feeding and satiety located within the brain?

A

Hypothalamus.

69
Q

What are the neural centers of the hypothalamus that which participate on the regulation of food intake?

A
  1. Lateral nucleus
  2. Ventromedial nucleus
  3. Paraventricular nucleus
  4. Dorsomedial nucleus
  5. Arcuate nucleus
70
Q

Which of the neural centers of the hypothalamus that which participate on the regulation of food intake is known as the feeding center?

A

Lateral nucleus

71
Q

Which of the neural centers of the hypothalamus that which participate on the regulation of food intake is known as the satiety center?

A

Ventromedial nucleus.

72
Q

Which of the neural centers of the hypothalamus that which participate on the regulation of food intake is known as the integrate center which feeds into the Lateral nucleus and ventromedial nucleus?

A

Arcuate nucleus.

73
Q

The hypothalamus receives many types of signal in regulating food intake. What are some of these signals?

A
  1. Neural siganls from the GI tract via the vagas n.
  2. Chemcial signals from nutrients in the blood
  3. Sigals from GI hormones like CCK and secretin
  4. signals from adipose tissue
  5. Signals from cerebral cortex (sight, smell and taste)
74
Q

Where is alpha -melanocortic stimulating hormone released from?

A

Pro-opiomelanocortin (POMC) neurons

75
Q

After a-MSH is released where does it bind to?

A

It binds to MCR-4 receptor.

76
Q

What is the result of a-MSH binding to MCR-4?

A

inhibits food intake and increases metabolism (anorexigenic)

77
Q

What stimulatory hormones activates POMC to release a-MSH and thus leading to decreased food intake?

A
  1. Insulin
  2. Leptin
  3. CCK.
78
Q

Insulin, leptin, and CCK inhibits the food intake pathway by blocking what?

A

LepR binding to AGRP/NPY

79
Q

Hunger signals stimulate the release of what peptide which then binds to Y1R to stimulate the neurons of the PVN and thus increases food intake.

A

Neuropeptide Y.

80
Q

Neurons that release neuropeptide Y also release what other peptide which is responsible for inhibiting PVN.

A

Agouti-related peptide (AGRP).

81
Q

AGRP is an antagonist for what receptor?

A

MCR-4

82
Q

What is the end result of the neuropeptide Y pathway?

A

Increase feeding behavior and storage of calories (orexigenic)

83
Q

Mutation in what genes can lead to obesity?

A

POMC and MCR-4

84
Q

What are some hormones that are released by the GI tract pancreas and adipose tissue which work to regulate feeding behavior?

A 
Ghrelin
Insulin
CCK
PYY
Leptin
Appetive-suppressing hormone
85
Q

Where are ghrelin secreted from

A

Secreted mainly by endocrine cells int he stomach

86
Q

Once released, what type of receptors do ghrelin bind to?

A

They bind to growth hormone secretagogue receptors

87
Q

In the hypothalamus, ghrelin stimulates neurons that release what peptide?

A

neuropeptide Y

88
Q

What are some other actions of ghrelin beside stimulating neurons that release NPY?

A

Ghrelin increases appetite, gastric motility, gastric acid secretion, adipogenesis and insulin secretion.

89
Q

In the hypothalamus, insulin binds to receptors in satiety and hunger centers and inhibits 1 pathway, and stimulates 2 pathway?

A
  1. inhibits NPY pathway

2. Stimulates POMC pathway

90
Q

Insulin acts to 1 (decrease/increase) appetite, and 2 (decrease/increase) metabolism.

A
  1. decrease

2. increase

91
Q

Compare food intake in patients with poorly controlled DM1 vs. normal.

A

Their food intake increases becuase their insulin level is decreased.

92
Q

CCK acts to elicits 1 (satiety or hunger), 2 (decrease or increaes) ghrelin; 3 (decrease or increase) gastric emptying; and 4 (decrease or increase) gastric distention.

A
  1. Satiety
  2. decrease
  3. decrease
  4. increase
93
Q

Following a meal, the L cells of the EEC of the ileum and colon releases what?

A

PYY

94
Q

What receptors do PYY bind to in the hypothalamus?

A

Y2

95
Q

When PYY binds to Y2, what happens to NPY neurons and POMC neurons?

A

NPY neurons are inhibited and releases inhibition of POMC neurons

96
Q

PYY acts as a potential appetite _ (supressor or stimulator)

A

supressor

97
Q

Where are leptin released from?

A

adipose tissue and endocrine cells in the stomach

98
Q

Leptin binds to receptors in satiety and hunger centers within the hypothalamus (POMC and NPY system) to 1 (inhibit or stimulate) NPY pathway; and 2 (stimulates or inhibit) POMC.

A
  1. inhibit

2. stimulate

99
Q

What hormone is involved in the negative feedback system for the regulation of food intake?

A

Appetive-suppressing hormone

GI Final (11 decks)

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