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GI Final Exam > Intro to GI physiology > Flashcards

Intro to GI physiology Flashcards

1
Q

What are the main functions of the GI tract?

A

-Digest and absorb nutrients

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2
Q

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

A

Motility and secretions

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3
Q

What restricts the passage of intestinal content to optimize digestion and absorption?

A

Sphincters

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4
Q

What are all of the sphincters of the GI tract?

A

UES, LES, Pylorus, Sphincter of Oddi, Ileocecal valve, Internal anal sphincter, External anal sphincter

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5
Q

What are the layers of the small intestine from outside to inside?

A

Epithelium, lamina propria, muscularis mucosae, submucosa, circular muscle, longitudinal muscle, and serosa

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6
Q

What are the functional layers of the small intestine?

A

Mucosal layer, submucosa, and muscle layers, and serosa

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7
Q

What is in the Mucosal layer?

A

from epithelium up to muscularis mucosae (the submucosa is its own functional layer)

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8
Q

What is in the muscularis propria?

A

Circular and longitudinal muscle

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9
Q

Where are the cell bodies in the extrinsic nervous system?

A

outside the gut wall

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10
Q

Where are the cell bodies int he intrinsic nervous system

A

within the wall of the gut

-example would be the enteric nervous system (ENS)

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11
Q

Where are the postganglionic neurons in the parasympathetic innervation?

A

they lie in the wall of the organ (enteric neuron in the gut wall)

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12
Q

Where do preganglionic efferent fibers end in the sympathetic innervation?

A

in the prevertebral ganglia

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13
Q

Where do the postganglionic fibers go in the sympathetic innervation?

A

they innervate the myenteric and submucosal plexuses just like the parasympathetics

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14
Q

What is the difference between what is released from the postganglionic fibers between symp and parasymp?

A

symp is NE onto adrenergic receptors
parasymp is Ach onto Muscarinic receptors
*remember that they both start with Ach onto Nicotinic receptors

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15
Q

What are the 3 plexuses for the sympathetic innervation outside of the GI tract?

A

Just like the arteries: Celiac, Superior mesenteric, and inferior mesenteric ganglia

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16
Q

What is the ENS innervated by?

A

the extrinsic nervous system

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17
Q

What is the extrinsic nervous system?

A

the thing that has cell bodies located outside the gut wall

-example would be the ANS

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18
Q

What is so special about the ENS?

A

it can exert its functions without CNS input

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19
Q

what secretes somatostatin?

A

D cells of the GI mucosa

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20
Q

What is the stimulus for somatostatin?

A

low luminal pH

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21
Q

What are the actions of somatostatin?

A

inhibits gastric H+ secretion

inhibits secretion of other GI hormones

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22
Q

What also secretes Somatostatin besides the d cells?

A

Hypothalamus and delta cells of the exocrine pancreas

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23
Q

Where is Histamine stored and secreted?

A

it’s in the stomach, by enterochromaffin like (ECL) cells in gastric glands

24
Q

What is the target of histamine?

A

parietal cells

25
Q

What is the action of histamine?

A

stimulate acid production

26
Q

What is the path of hormones once they are released from the GI tract?

A

into the portal circulation, pass through the liver, and reach systemic circulation to bind to specific receptors on target cell

27
Q

What is the hormone family, site of secretion , and stimuli of secretion for Gastrin?

A
  • Gastrin-CCK,
  • G-cells of stomach,
  • small peptides and aa’s, distention of stomach, and vagal stimulation
28
Q

What is the hormone family, site of secretion, and stimuli of secretion for CCK?

A
  • gastrin CCK
  • I cells of the duodenum and jejunum
  • small peptide and aa’s, fatty acids
29
Q

What is the hormone family, site of secretion, and stimuli of secretion for secretin?

A
  • secretin glucagon
  • S cells of the duodenum
  • H+ in the duodenum, fatty acids in the duodenum
30
Q

What is the hormone family, site of secretion, and stimuli for GIP

A

secretin glucagon,

  • Duodenum and jejunum
  • Fatty acids, aa’s, and oral glucose
31
Q

What are the actions of Gastrin?

A

increase gastric acid secretion

stimulates growth of gastric mucosa (trophic effect)

32
Q

What is Sollinger-Ellison syndrome?

A

Gastrin secreting tumors!
-increased circulating levels of gastrin and acid secretion by parietal cells, hypertrophy of the gastric mucosa, duodenal ulcers, and steatorrhea

33
Q

What is steatorrhea?

A

the increased excretion of fat in the feces due to insufficient absorption of fat by the intestine

34
Q

What are the actions of CCK?

A
  • increase pancreatic enzyme secretion and pancreatic bicarb secretion (indirectly)
  • stimulates contraction of the gallbladder and relaxation of the sphincter of Oddi
  • stimulates growth of the exocrine pancreas and gallbladder (trophic effect)
  • inhibits gastric epmtying
  • can also act as a paracrine signal
35
Q

What are the actions of Secretin?

A
  • Increased pancreatic bicarb secretion (THIS IS THE DIRECT CAUSE OF BICARB SECRETION)
  • Increased biliary bicarb secretion
  • decreased gastric H+ secretion
  • inhibits trophic effect of gastrin on the gastric mucosa
  • can also act as a paracrine signal
36
Q

What are the 2 things that GIP could mean?

A

glucose dependent insulinotropic peptide
OR
gastric inhibitory peptide

37
Q

What are the actions of GIP?

A
  • increase insulin secretion form pancreatic B cells

- decreased gastric H+ secretion

38
Q

What would be more effenctive in increasing insulin secretion? Oral or intravenous glucose administration?

A

oral because that is a stimulus for GIP in the duodenum and jejunum

39
Q

What is the source and action of Ach?

A
  • cholinergic neurons
  • contraction of smooth muscle, relastation of sphincters, increased salivary secretion, gastric secretion, and pancreatic secretion…. IT MAKES US DIGEST STUFF!
40
Q

What is the source and action of NE?

A
  • adrenergic neurons

- relaxation of smooth muscle, contraction of sphincters, and increased salivary secretion

41
Q

What is the source and action of Vasoactive instestinal peptide? (VIP)

A
  • neurons of the mucosa and smooth muscle

- relaxation of smooth muscle, increased intestinal and pancreatic secretions

42
Q

What is the source and actions of Gastrin-releasing peptide (GRP)?

A
  • Neurons from gastric mucosa

- increased gastrin secretion

43
Q

What is the source and actions of Enkephalins?

A
  • neurons of the mucosa and smooth muscle

- contraction of smooth muscle, decreased intestinal secretion

44
Q

What is the source and actions of neuropeptide Y?

A
  • neurons of the mucosa and smooth muscles

- relaxation of smooth muscle, decreased intestinal secretion

45
Q

What is the source and actions of substance P?

A
  • co-release with Ach

- contraction of smooth muscle and increased salivary secretion

46
Q

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

A

-Lateral nucleus
-ventromedial nucleus
-paraventricular
dorsomedial
arcuate

47
Q

Where does most of the integration signaling regulating food intake and energy expenditure happen?

A

int he arcuate nucleus of the hypothalamus

48
Q

What are the 2 pathways int he arcuate nucleus?

A 
alpha melanocortin (a-MSH)
Neuropeptide Y (NPY)
49
Q

How does the MSH pathway work?

A
  • it’s released by POMC neurons
  • binds to MCR-4 present in second order neurons
  • *INHIBITS FOOD INTAKE AND INCREASES METABOLISM
50
Q

How does the NPY pathway work?

A
  • hunger signals stimulate the release of NPY
  • binds to Y1R
  • neurons that release NPY also release AGRP
  • AGRP is an antagonist of MCR-4
  • INCREASES FEEDING BEHAVIOR AND STORAGE OF CALORIES
51
Q

What is important to note about the MSH and NPY pathways?

A

They antagonize each other

52
Q

Describe Ghrelin

A
  • comes from stomach
  • binds to growth hormone secretagogue receptors
  • IN THE HYPOTHALAMUS, IT STIMULATES NEURONS THAT RELEASE NPY**
  • so basically, it makes us grow
53
Q

What does insulin do?

A

binds receptors in POMC and NPY pathways

-Increases metabolism and decreases apetite

54
Q

What does CCK do?

A
  • released by I cells in the duodenum
  • elicits satiety: actons of Vagal, NTS, hypothalamus circui
  • stops ghrelin and gastric emptying
55
Q

What does peptide YY (PYY) do?

A

released by EEC’s on the ileum and colon following a meal

-binds Y2 receptors of the hypothalamus to INHIBIT NPY NEURONS AND RELEASE INHIBITION OF THE POMC NEURONS

56
Q

What does Leptin do?

A

The same thing as insulin but it also decreases ghrelin release

GI Final Exam (10 decks)

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