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Physiology II > Exam #4: GI > Flashcards

Exam #4: GI Flashcards

1
Q

Four hormones of GI tract?

A
  • Gastrin
  • CCK
  • Secretin
  • GIP
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2
Q

Two paracrine of GI tract?

A
  • Somatostatin

- Histamine

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3
Q

Four neurocrines of GI tract?

A
  • ACh
  • NE
  • VIP
  • GRP
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4
Q

Which ANS is inhibitory (synapse at ganglia)?

A

SNS

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5
Q

Which ANS is excitatory (directly innervates gut)?

A

PNS

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6
Q

Layers of GI tract (7)?

A 
OUTER
- Serosa
- Longitudinal muscle
- Myenteric plexus
- Circular muscle
- Submucosa
- Submucosal plexus
- Mucosa
INNER
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7
Q

Which nerve plexus involves muscle movement?

A

Myenteric plexus

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8
Q

Which nerve plexus involves intestinal secretion/absorption?

A

Submucosal plexus

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9
Q

Which sections of the GI tract are skeletal muscle? Which are smooth muscle?

A
  • Skeletal: mouth, anal

- Smooth muscle: everything in between (mid-esophagus to internal anal sphincter)

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10
Q

What increases BER amplitude? What decreases it (2)?

A
  • ACh increases BER amplitude (NOT frequency)

- NE/Epi decrease BER amplitude

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11
Q

In visceral smooth muscle cells, tone is proportional to…?

A 
# of APs
- More APs = more tone
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12
Q

What is the cyclical motor activity to remove undigested material from stomach and small intestine – slow, intense? What general phase is it involved in? What is the purpose of the phase?

A

MMC (Migrating Motor Complex) of the Interdigestive Phase

- Ensures contents do not sit stagnant/cause bacterial buildup

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13
Q

What is the MMC (Migrating Motor Complex) regulated by?

A

Motilin

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14
Q

What is the role of alpha-amylase in saliva? Lingual lipase?

A
  • Alpha-amylase = digest starches

- Lingual lipase = digest fats

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15
Q

What is the osmolarity of saliva in acinar cells? What about in ductal cells, and why?

A
  • Acinar cells = isotonic

- Ductal cells = hypotonic (cells NOT permeable to water, Na and Cl removed from saliva/added to blood)

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16
Q

At high flow rates, what is the osmolarity of saliva, and why?

A

Saliva = isotonic at HIGH flow rates

- Increase Na and Cl with high HCO3

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17
Q

What is salivary secretion mostly regulated by?

A

PNS (ACh and VIP)

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18
Q

What four conditions can increase salivary secretion?

A
  • Conditioning
  • Food
  • Nausea
  • Smell
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19
Q

What three conditions can decrease salivary secretion?

A
  • Dehydration
  • Fear
  • Sleep
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20
Q

What is swallowing coordinated by?

A

Medullary swallowing center (initially voluntary, then reflexive)

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21
Q

What are the three phases of swallowing, and which is partially non-reflexive?

A
  1. Oral (non-reflexive)
  2. Pharyngeal
  3. Esophageal
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22
Q

What three steps occur in the oral phase of swallowing (note voluntary vs. involuntary)?

A
  1. Mastication forms bolus
  2. Tongue pushes bolus towards pharynx VOLUNTARY
  3. Somatosensory receptors in pharynx initiate INVOLUNTARY swallow reflex in medulla
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23
Q

What five steps occur in the pharyngeal phase of swallowing?

A

ALL REFLEXIVE

  1. Soft palate pulled upward to prevent nasopharynx reflux
  2. Epiglottis moves to cover larynx
  3. Larynx moves upward against epiglottis to prevent food from entering trachea
  4. UES inhibited and relaxes briefly
  5. Peristaltic wave propels food through UES into esophagus
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24
Q

What two steps occur in the esophageal phase of swallowing?

A

ALL REFLEXIVE

  1. Peristaltic wave further propels food down esophagus toward LES
  2. LES relaxes via VIP then contracts as bolus passes into stomach
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25
Q

What is a second swallow?

A

2nd peristaltic wave controlled by ENS if incomplete swallowing/regurgitation

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26
Q

At what two areas are esophageal pressures highest?

A

UES and LES

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27
Q

Role of ACh?

A

PNS = excitatory

- Increases secretions and motility

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28
Q

Role of NE?

A

SNS = inhibitory

- Decreases motility

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29
Q

Role of VIP (2)?

A

PNS and ENS

  • Increase secretions
  • Decrease motility
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30
Q

What organ uses receptive relaxation, and what does this mean?

A

Stomach

- Proximal stomach (fundus) relaxes, allows for easy passage of food from esophagus

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31
Q

Gastric Pits are found in what portion of the stomach? What two cell types are present here?

A

BODY

  • Parietal cells
  • Chief cells
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32
Q

Pyloric Glands are found in what portion of the stomach? What two cell types are present here?

A

ANTRUM

  • G cells
  • Mucous cells
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33
Q

What cell type secretes Gastrin? What is its primary role?

A

G cells

- Increase gastric H+

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34
Q

What cell type secretes CCK? What is its primary role?

A

I cells

- Increase pancreatic HCO3

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35
Q

What cell type secretes Secretion? What is its primary role?

A

S cells

  • Increase pancreatic HCO3
  • Decrease gastric H+
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36
Q

What secretes GIP (2)? What is its primary role?

A

Duodenum, jejunum

- Decrease gastric H+

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37
Q

What three things stimulate Gastrin release?

A
  • AAs in stomach
  • Stomach distention
  • Vagal stimulation (GRP)
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38
Q

What two things stimulate CCK release?

A
  • AAs

- FAs

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39
Q

What two things stimulate Secretin release?

A
  • H+ in duodenum

- FAs in duodenum

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40
Q

What three things stimulate GIP release?

A
  • AAs
  • FAs
  • Oral glucose
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41
Q

What is the goal of HCl secretion in the stomach?What are three ways by which this occurs?

A

Increase proton pump activity (H/K)

  • Gastrin binds CCKb receptor
  • ECL cells release histamine and histamine binds H2 receptors
  • Vagus n. stimulation by ACh
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42
Q

What phase is most important for HCl secretion? What occurs during this phase to enhance HCl secretion (2)?

A

Gastric phase

Distention of stomach stimulates HCl secretion via…

  • LOCAL reflex arc
  • VAGOVAGAL reflex arc
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43
Q

What phase is most important for Pepsinogen secretion? What occurs during this phase to enhance Pepsinogen secretion?

A

Cephalic phase

- Vagus n. directly stimulates chief cells to release Pepsinogen

44
Q

What cell type secretes Pepsinogen, and what activates it to Pepsin?

A

Chief cells

- Activated by acids to become Pepsin

45
Q

Gastric Mucosal Barrier (GMB) creates what? What three things can damage the GMB?

A

GMB creates pH gradient

Damaged by…

  • High acid/pepsin
  • H. pylori
  • NSAIDs
46
Q

What are the three components of gastric motility?

A
  • Receptive relaxation
  • Segmentation (mixing motions to reduce bolus size)
  • Peristalsis (chyme propulsion into duodenum)
47
Q

What are the two primary components of pancreatic juice, and what cell type provides each?

A
  • Digestive enzymes = acinar cells

- Aqueous portion with bicarb = centroacinar cells AND ductal cells

48
Q

What are the three phases of pancreatic stimulation, and which is most important?

A
  • Cephalic phase
  • Gastric phase
  • Intestinal phase = MOST important (CCK with enzymes and Secretin with HCO3)
49
Q

What two hormones are utilized for pancreatic secretions, and what does each secrete?

A
  • CCK = enzyme production

- Secretin = HCO3 production

50
Q

What is the low resistance pathway taken by blood from the GI tract (5 steps)?

A

GI → hepatic portal veins → sinusoids (capillary) → central vein → vena cava

51
Q

In the liver, ____ are fenestrated, and tight junctions separate ____ from ____?

A
  • Sinusoids are fenestrated

- Bile canaliculi are separated from sinusoids via tight junctions

52
Q

What are the four components of bile and which is most prevalent?

A
  • Bile salts = MOST prevalent
  • Phospholipids
  • Cholesterol
  • Bile pigments (like bilirubin)
53
Q

Bile is made by the ____ and stored in the ____?

A
  • Made in the liver

- Stored in the gallbladder

54
Q

What phase of pancreatic stimulation involves enzymes and HCO3 secretion via the PNS?

A

Cephalic

55
Q

What is an important aspect of primary bile salts production? Secondary bile salts? Conjugated bile salts?

A
  • Primary = made by liver
  • Secondary = made by bacteria in intestines
  • Conjugated = bile acid + glycine/taurine → lowers pH
56
Q

Three etiologies of jaundice, and possible cause of each?

A
  • Prehepatic = hemolytic (RBC lysis → pernicious anemia, infants)
  • Hepatic = liver disease (ex. cirrhosis, Gilbert’s)
  • Posthepatic = obstructive (bile duct blocked)
57
Q

In the gallbladder, what portion does CCK contract, and what does it relax? What occurs when CCK is PRESENT?

A

If CCK present = bile flows

  • Gallbladder contracts via CCK
  • Sphincter of Oddi relaxes via CCK
58
Q

What portion of the intestines absorbs bile salts? What else is absorbed here?

A

Ileum absorbs bile salts

- Also absorbs Vitamin B12

59
Q

Synthesis of bile salts is inversely related to what? What is the enzyme of bile acid production, and what inhibits it?

A

Reabsorption of bile salts

- Cholesterol 7alpha-hydroxylase is inhibited by bile salts

60
Q

What is the primary role of the small intestines (2)? What three characteristics allow for this to better occur, and what is their primary role?

A

Digestion and absorption of NUTRIENTS

INCREASED surface area

  • Kerckring’s folds
  • Villi
  • Microvilli
61
Q

What is the purpose of segmentation in the small intestines?

A

Mixes chyme and brings fresh chyme (with enzymes) into mucosal contact

62
Q

What is the technique used by the small intestines during peristalsis, and what does this involve (2 hormones)?

A

ORTHOGRADE WAVE

  • Circular muscles in front of bolus RELAX via VIP
  • Circular muscles behind bolus CONTRACT via ACh
63
Q

What are the two types of motility in the small intestines, and which is the primary method?

A
  • Segmentation = mixing

- Peristalsis = propulsion (PRIMARY method)

64
Q

What are the two neural components of small intestine motility?

A
  • PNS (Vagus n.) = stimulate intestinal contractions

- SNS = inhibit intestinal contractions

65
Q

What are the four intestinal reflexes? Which one is inhibitory?

A
  • Enterogastric = INHIBITORY
  • Gastroileal = EXCITATORY
  • Ileocecal = EXCITATORY
  • Gastrocolic = EXCITATORY
66
Q

What four neurohormonal factors increase intestinal motility?

A
  • ACh
  • Gastrin
  • CCK
  • Motilin
67
Q

What four neurohormonal factors decrease intestinal motility?

A
  • NE
  • Somatostatin
  • Secretin
  • VIP
  • GIP
68
Q

Where are Crypts of Lieberkühn found, and what is their primary purpose (2)?

A

Found between individual villi in small intestines

  • Produce new enterocytes
  • Secrete mucous
69
Q

Where are Brush Border cells found, and what do they secrete/what is the purpose of this enzyme?

A

Found on microvilli of small intestines

- Secrete enterokinase → activates pancreatic enzymes

70
Q

In what two ways is the large intestine different from the small intestine (think anatomy)?

A
  • NO villi (less absorption)

- Thicker mucosa due to more goblet cells

71
Q

What type of muscle makes up the internal anal sphincter? What type of muscle makes up the external anal sphincter? Which is voluntary and which is involuntary?

A
  • Internal anal sphincter = circular muscle (involuntary)

- External anal sphincter = striated muscle (voluntary)

72
Q

What two intestinal reflexes act on the ileocecal sphincter?

A
  • Gastroileal: gastric activity increases ileal motility

- Ileocecal reflex: ileal distention relaxes ileocecal sphincter

73
Q

What is the primary substance absorbed by the large intestine?

A

WATER

74
Q

What portion of the GI tract synthesizes vitamins?

A

COLON in large intestines

75
Q

What are the two neural components of large intestine motility? What are the subtypes of each (2 each)?

A

PNS = excitatory

  • Vagus n. = ascending colon, transverse colon
  • Pelvic n. = descending colon, sigmoid colon, rectum

SNS = inhibitory
- Superior and inferior mesenteric ganglions

76
Q

With PNS neural component in large intestine, what are the two types and where does each act (2, 3)?

A

PNS = excitatory

  • Vagus n. = ascending colon, transverse colon
  • Pelvic n. = descending colon, sigmoid colon, rectum
77
Q

What are the two types of motility in the large intestines?

A
  • Haustration = mixing

- Mass movement (gastrocolic reflex)

78
Q

What is the gastrocolic reflex and in what part of the GI tract is it used?

A

Same as mass movement = ascending and descending colons contract simultaneously and drive feces through colon within seconds
- Most evident after first meal of day

79
Q

What portion of the GI tract involves longitudinal muscle separated by taeniae coli (3 bands); haustra?

A

Large intestines

80
Q

Explain the process of defecation?

A

As rectal pressure increases, the rectal muscle contracts and IAS relaxes, EAS is contracted
- When ready, EAS relaxes = BM

81
Q

What enzyme breaks down complex sugars to oligosaccharides, and what are these five oligosaccharides?

A

AMYLASE

  • Lactose
  • Alpha-dextrins
  • Maltotriose
  • Maltose
  • Sucrose
82
Q

Where are oligosaccharides broken down to simple sugars, and what are these three simple sugars?

A

At brush border

  • Glucose
  • Fructose
  • Galactose
83
Q

What enzyme breaks down Lactose, and what two simple sugars is it broken down to?

A

Lactase

  • Glucose
  • Galactose
84
Q

What two enzymes break down Alpha-dextrin, and what simple sugar is it broken down to?

A

Maltase and Alpha-dextrinase

- Glucose

85
Q

What three enzymes break down Maltotriose, and what simple sugar is it broken down to?

A

Maltase, Sucrase, Alpha-dextrinase

- Glucose

86
Q

What three enzymes break down Maltose, and what simple sugar is it broken down to?

A

Maltase, Sucrase, Alpha-dextrinase

- Glucose

87
Q

What enzyme breaks down Sucrose, and what two simple sugars is it broken down to?

A

Sucrase

  • Glucose
  • Fructose
88
Q

What simple sugar are most carbs digested into?

A

Glucose

89
Q

What transporter is found at the apical membrane to transport simple sugars/carbs, and which two carbs are transported here? How is this transporter regulated?

A

SGLT1 transport glucose and galactose

- Na-dependent

90
Q

What transporter is found at the basolateral membrane to transport simple sugars/carbs, and which two carbs are transported here?

A

GLUT2 transports glucose/galactose

91
Q

What two transporters are used to transport Fructose, and how does this occur?

A

DIFFUSION (not active)

  • GLUT5 on apical mem.
  • GLUT2 on basolateral mem.
92
Q

What enzyme converts trypsinogen to trypsin, and what is the role of trypsin?

A

Enteropeptidase: trypsinogen → trypsin

- Trypsin activates inactive pancreatic enzymes in small intestine

93
Q

Where are oligopeptides broken down, and what three things are they broken down to? What enzyme does this?

A

At brush border, oligosaccharides become…

  • AAs
  • Dipeptides
  • Tripeptides

PERFORMED BY PEPTIDASES

94
Q

What type of transport is used for AAs? What type of transport is used for dipeptides/tripeptides?

How do these enter cells

A
  • AAs = Na transport
  • Dipeptides/tripeptides = H+ transport

All three enter cells via carriers

95
Q

What enzyme converts TGs → FFAs?

A

Pancreatic Lipase

96
Q

What enzyme converts cholesterolester → cholesterol?

A

Cholesterolester Hydrolase

97
Q

What enzyme converts lecithin → lysolecithin?

A

Phospholipase A2

98
Q

Three steps of fat transport/reabsorption?

A
  1. Micelles formed in small intestine = TGs, FFAs, cholesterols packaged inside for transport, then micelles diffuse across brush border into small intestine and release contents
  2. Lipids reassembled and packaged into chylomicrons
  3. Chylomicrons transported into lacteals then enter lymph → blood
99
Q

How do Fat-Soluble vitamins differ from Water-Soluble vitamins in terms of transport?

A
  • Fat-Soluble = processed like fats so micelles and chylomicrons
  • Water-soluble: Na-dependent transporters
100
Q

Where does calcium absorption occur, and what can increase this? What is the role of this substance?

A

At Brush Border

- Increased CaBP → moves Ca2+ from apical membrane to basolateral membrane then out of cell (into blood)

101
Q

Is more iron ingested or absorbed?

A

MORE INGESTED

102
Q

What two proteins are involved in iron absorption, and what is the role of each?

A
  • Transferrin = transport

- Ferritin = storage

103
Q

How does water movement occur in the intestines?

A

Follows solutes/coupled to Na

104
Q

What two substances are reabsorbed at the jejunum?

A
  • Na

- HCO3

105
Q

What two substances are reabsorbed at the ileum?

A
  • Na

- Cl

106
Q

What renal structure is the small intestine similar to? Large intestine?

A
  • SI: proximal tubule

- LI: collecting duct

107
Q

What two substances are reabsorbed by the large intestine, and how?

A
  • Na via ENaC (induced by Aldosterone)

- K via diffusion

Physiology II (5 decks)

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