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BMS 150 Final > Physiology of the GI tract and intro to Gut Microbiome > Flashcards

Physiology of the GI tract and intro to Gut Microbiome Flashcards

1
Q

what are the 3 basic movements that take place along the GI tract?

A
  • peristalsis
  • segmentation
  • migrating motor complex (MMC)
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2
Q

peristalsis involves what?

A

entire GI tract, starting with esophagus

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3
Q

what is peristalsis?

A

waves of smooth muscle contractions that propel food bolus throughout GI tract

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4
Q

what type of movement can be stimulated or promoted by distention of smooth muscle cells?

A

peristalsis

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5
Q

what is the function of peristalsis?

A

propel food further along GI tract

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6
Q

what involves contraction behind (proximal) the food bolus and relaxation in front (distal) of the food bolus

A

peristalsis

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7
Q

where does segmentation occur?

A

within SI and LI

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8
Q

how is segmentation produced?

A

produced by the coordination of smooth muscle cells and interstitial cells of Cajal (ICC)

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9
Q

what is the function of segmentation?

A

promote mixing the food particles to increase interaction between the villi of the enterocytes and various food particles to promote absorption

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10
Q

where does migrating motor complex occurs?

A

within stomach and SI (and a few other locations)

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11
Q

what is migrating motor complex?

A

Small movement, almost a vibration, that occurs predominantly during fasting 1.5-2 hr intervals

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12
Q

the movement of migrating motor complex is promoted by ?, secreted by? located in the ?

A

motilin
Mo-cells
duodenum

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13
Q

what is the function of migrating motor complex?

A

suspected that it is a self-cleaning mechanism, as this movement causes small food particles and bacteria to be dislodged from the intestinal wall and prevents bacteria from traveling from LI into SI

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14
Q

what is the pacemakers of the GI?

A

interstitial cells of cajal (ICC)

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15
Q

what is interstital cells of Cajal?

A

Form a network with each other and smooth muscle cells via gap junctions, as well as enteric motor neurons

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16
Q

what generate slow waves and can cause spike potentials that do trigger smooth muscle contractions

A

the interstitial cells of cajal

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17
Q

excitability of smooth muscles can be increased by additional factors such as:

A
  • Muscle stretch (distention)
  • Acetylcholine
  • Other GI hormones
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18
Q

excitability of smooth muscles can be decreased by additional factors such as:

A
  • Norepinephrine (causes hyperpolarization)
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19
Q

Enteric Nervous System is composed of ?

A

sensory, motor, and interneurons

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20
Q

the ENS is organized into ?

A

Submucosal plexus and myenteric plexus

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21
Q

submucosal plexus is located ?

A

Located between the layers of submucosa and circular muscle (only present in SI and LI)

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22
Q

what is the function of submucosal plexus?

A

Function to regulate motility, local blood flow, regulate secretions and epithelial cell function

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23
Q

myenteric plexus is located ?

A

Located between longitudinal and circular muscles (entire GI)

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24
Q

what is the function of myenteric plexus?

A

Function to regulate motility

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25
Q

what are some examples of nerves that connect CNS and ENS

A

○ Vagus Nerve
○ Pelvic Splanchnic Nerves
○ Thoracic Sympathetic Trunk

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26
Q

what is key when it comes to transport throughout the GI tract

A

timing

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27
Q

what happens if food is transported too quickly

A

may not have enough time to digest or absorb it

28
Q

what happens when the food is transported too slowly

A

it may irritate the local or neighboring mucosa

29
Q

what secretions promotes motility?

A

○ I-cells – cholecystokinin
○ Enterochromaffin cells – serotonin
○ G-cells – gastrin
○ Mo-cells – motilin
- Beta-pancreatic cells – insulin

30
Q

what secretions reduces motility?

A

○ S-cells – secretin
○ D-cells – somatostatin
○ Pancreatic cells - Pancreatic peptide YY
○ Alpha-pancreatic cells – glucagon

31
Q

what is digestion?

A

breaking down macromolecules into smaller molecules to increase absorption

32
Q

what are the 2 major types of digestion?

A

mechanical digestion and chemical digestion

33
Q

what is mechanical digestion?

A

physically cutting, crushing, and churning food so that the volume of each food particle decreases

34
Q

what is the chemical digestion?

A

chemical processes that allows absorption of food particles

35
Q

what is enzymatic digestion

A

enzymes break macronutrients down into smaller and smaller particles through the process of hydrolysis

36
Q

what is lipid solubilization?

A

emulsifiers (bile salts, lecithin) secreted by the liver emulsify ingested lipids so that enzymes can break them down to smaller, absorbable molecules

37
Q

what is the carbohydrate digestion?

A

begins in the mouth with salivary amylase (minority), further broken down by pancreatic amylase and brush border enzymes within SI (majority of CHO digestion)

38
Q

what is protein digestion?

A

begins in the stomach with HCL and pepsin, further digested by pancreatic enzymes and brush border enzymes

39
Q

what is fat digestion?

A

begins in the stomach with HCl and lipase (minority), further digested by pancreatic lipase and emulsified by bile acids released by the liver (majority of lipid digestion)

40
Q

what is absorption?

A

movement of any substance across the mucosal epithelium of the alimentary tract and into the bloodstream (most substances) or lymphatics (lipids)

41
Q

where does absorption largely takes place in?

A

in the small intestine

42
Q

effective absorption is dependent on

A

a large surface area at the apex of the epithelial cell

43
Q

only what can be transported across the epithelial cells of the small intestine, in terms of carbohydrate?

A

monosaccharides

44
Q

what transports glucose and galactose from lumen into enterocyte

A

Na+/glucose (galactose) co-transporter

45
Q

what is the passive transport of fructose from lumen into enterocyte

A

GLUT-5

46
Q

what transports the monosaccharides from enterocyte into blood stream (hepatic portal vein)

A

GLUT-2 and GLUT-5 basolateral side

47
Q

majority of protein is absorbed in the ?

A

duodenum and jejunum

48
Q

what are the transporters of protein absorption?

A

Na+ symporters and PepT1 transporter

49
Q

what transports dipeptides and tripeptides into enterocyte

A

PepT1 transporter

50
Q

which protein transporter relies in H+ instead of Na+ concentration gradient

A

PepT1 transporter

51
Q

nucleic acids are broken into ? and further broken into ? and ? via digestion

A

nucleotides
nucleoside
phosphoric acid

52
Q

how are fat absorbed?

A

passive diffusion

53
Q

what are chylomicron?

A

FFA’s and cholesterol are coated with proteins, more cholesterol and phospholipids

54
Q

what is steatorrhea

A

impaired fat digestion and absorption result in high amount of fat in the stool

55
Q

where are vitamins absorbed?

A

Majority absorbed in duodenum (upper SI), however vitamin B12 is absorbed in the ileum

56
Q

For absorption, Most of the B-vitamins and vitamin C require what

A

Na+ cotransporters for absorption

57
Q

where does iron get absorbed?

A

Occurs within duodenum via divalent metal transporter 1 (DMT1) – Fe2+ (ferrous) enters enterocytes

58
Q

What is the microbiome?

A

The collection of all organisms living on and in a given environment or habitat

59
Q

what is the human microbiome project

A

the catalog of the microbes in human and their genes

60
Q

what bacteria are in the oral cavity?

A

spirochaetes

61
Q

what bacteria are in the stomach

A

Helicobacter pylori

62
Q

what bacteria are in the small intestine

A

lactobacili, gram positive cocci

63
Q

what are the major compositions of the gut microbiome

A

firmicutes and bacteroidetes

64
Q

what is bacteriostatic?

A

Mechanism of action interferes with bacterial cell activity (including replication) without directly causing death

65
Q

what is bactericidal?

A

○ Mechanism of action directly kills the bacteria

66
Q

what does the broad spectrum mean?

A

Antibiotic is able to effect different types of bacteria’s including gram positive, gram negative, and others (spirochetes, atypical)

67
Q

what is antibiotic associated diarrhea?

A

○ Caused by disruption in normal gut microbiome
§ C. difficile accounts for 10-25% of AAD cases

BMS 150 Final (5 decks)

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