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Physiology II > Exam #4: GI > Flashcards

Exam #4: GI Flashcards

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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
What is a second swallow?
2nd peristaltic wave controlled by ENS if incomplete swallowing/regurgitation
26
At what two areas are esophageal pressures highest?
UES and LES
27
Role of ACh?
PNS = excitatory | - Increases secretions and motility
28
Role of NE?
SNS = inhibitory | - Decreases motility
29
Role of VIP (2)?
PNS and ENS - Increase secretions - Decrease motility
30
What organ uses receptive relaxation, and what does this mean?
Stomach | - Proximal stomach (fundus) relaxes, allows for easy passage of food from esophagus
31
Gastric Pits are found in what portion of the stomach? What two cell types are present here?
BODY - Parietal cells - Chief cells
32
Pyloric Glands are found in what portion of the stomach? What two cell types are present here?
ANTRUM - G cells - Mucous cells
33
What cell type secretes Gastrin? What is its primary role?
G cells | - Increase gastric H+
34
What cell type secretes CCK? What is its primary role?
I cells | - Increase pancreatic HCO3
35
What cell type secretes Secretion? What is its primary role?
S cells - Increase pancreatic HCO3 - Decrease gastric H+
36
What secretes GIP (2)? What is its primary role?
Duodenum, jejunum | - Decrease gastric H+
37
What three things stimulate Gastrin release?
- AAs in stomach - Stomach distention - Vagal stimulation (GRP)
38
What two things stimulate CCK release?
- AAs | - FAs
39
What two things stimulate Secretin release?
- H+ in duodenum | - FAs in duodenum
40
What three things stimulate GIP release?
- AAs - FAs - Oral glucose
41
What is the goal of HCl secretion in the stomach?What are three ways by which this occurs?
Increase proton pump activity (H/K) - Gastrin binds CCKb receptor - ECL cells release histamine and histamine binds H2 receptors - Vagus n. stimulation by ACh
42
What phase is most important for HCl secretion? What occurs during this phase to enhance HCl secretion (2)?
Gastric phase Distention of stomach stimulates HCl secretion via... - LOCAL reflex arc - VAGOVAGAL reflex arc
43
What phase is most important for Pepsinogen secretion? What occurs during this phase to enhance Pepsinogen secretion?
Cephalic phase | - Vagus n. directly stimulates chief cells to release Pepsinogen
44
What cell type secretes Pepsinogen, and what activates it to Pepsin?
Chief cells | - Activated by acids to become Pepsin
45
Gastric Mucosal Barrier (GMB) creates what? What three things can damage the GMB?
GMB creates pH gradient Damaged by... - High acid/pepsin - H. pylori - NSAIDs
46
What are the three components of gastric motility?
- Receptive relaxation - Segmentation (mixing motions to reduce bolus size) - Peristalsis (chyme propulsion into duodenum)
47
What are the two primary components of pancreatic juice, and what cell type provides each?
- Digestive enzymes = acinar cells | - Aqueous portion with bicarb = centroacinar cells AND ductal cells
48
What are the three phases of pancreatic stimulation, and which is most important?
- Cephalic phase - Gastric phase - Intestinal phase = MOST important (CCK with enzymes and Secretin with HCO3)
49
What two hormones are utilized for pancreatic secretions, and what does each secrete?
- CCK = enzyme production | - Secretin = HCO3 production
50
What is the low resistance pathway taken by blood from the GI tract (5 steps)?
GI → hepatic portal veins → sinusoids (capillary) → central vein → vena cava
51
In the liver, ____ are fenestrated, and tight junctions separate ____ from ____?
- Sinusoids are fenestrated | - Bile canaliculi are separated from sinusoids via tight junctions
52
What are the four components of bile and which is most prevalent?
- Bile salts = MOST prevalent - Phospholipids - Cholesterol - Bile pigments (like bilirubin)
53
Bile is made by the ____ and stored in the ____?
- Made in the liver | - Stored in the gallbladder
54
What phase of pancreatic stimulation involves enzymes and HCO3 secretion via the PNS?
Cephalic
55
What is an important aspect of primary bile salts production? Secondary bile salts? Conjugated bile salts?
- Primary = made by liver - Secondary = made by bacteria in intestines - Conjugated = bile acid + glycine/taurine → lowers pH
56
Three etiologies of jaundice, and possible cause of each?
- Prehepatic = hemolytic (RBC lysis → pernicious anemia, infants) - Hepatic = liver disease (ex. cirrhosis, Gilbert’s) - Posthepatic = obstructive (bile duct blocked)
57
In the gallbladder, what portion does CCK contract, and what does it relax? What occurs when CCK is PRESENT?
If CCK present = bile flows - Gallbladder contracts via CCK - Sphincter of Oddi relaxes via CCK
58
What portion of the intestines absorbs bile salts? What else is absorbed here?
Ileum absorbs bile salts | - Also absorbs Vitamin B12
59
Synthesis of bile salts is inversely related to what? What is the enzyme of bile acid production, and what inhibits it?
Reabsorption of bile salts | - Cholesterol 7alpha-hydroxylase is inhibited by bile salts
60
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?
Digestion and absorption of NUTRIENTS INCREASED surface area - Kerckring’s folds - Villi - Microvilli
61
What is the purpose of segmentation in the small intestines?
Mixes chyme and brings fresh chyme (with enzymes) into mucosal contact
62
What is the technique used by the small intestines during peristalsis, and what does this involve (2 hormones)?
ORTHOGRADE WAVE - Circular muscles in front of bolus RELAX via VIP - Circular muscles behind bolus CONTRACT via ACh
63
What are the two types of motility in the small intestines, and which is the primary method?
- Segmentation = mixing | - Peristalsis = propulsion (PRIMARY method)
64
What are the two neural components of small intestine motility?
- PNS (Vagus n.) = stimulate intestinal contractions | - SNS = inhibit intestinal contractions
65
What are the four intestinal reflexes? Which one is inhibitory?
- Enterogastric = INHIBITORY - Gastroileal = EXCITATORY - Ileocecal = EXCITATORY - Gastrocolic = EXCITATORY
66
What four neurohormonal factors increase intestinal motility?
- ACh - Gastrin - CCK - Motilin
67
What four neurohormonal factors decrease intestinal motility?
- NE - Somatostatin - Secretin - VIP - GIP
68
Where are Crypts of Lieberkühn found, and what is their primary purpose (2)?
Found between individual villi in small intestines - Produce new enterocytes - Secrete mucous
69
Where are Brush Border cells found, and what do they secrete/what is the purpose of this enzyme?
Found on microvilli of small intestines | - Secrete enterokinase → activates pancreatic enzymes
70
In what two ways is the large intestine different from the small intestine (think anatomy)?
- NO villi (less absorption) | - Thicker mucosa due to more goblet cells
71
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?
- Internal anal sphincter = circular muscle (involuntary) | - External anal sphincter = striated muscle (voluntary)
72
What two intestinal reflexes act on the ileocecal sphincter?
- Gastroileal: gastric activity increases ileal motility | - Ileocecal reflex: ileal distention relaxes ileocecal sphincter
73
What is the primary substance absorbed by the large intestine?
WATER
74
What portion of the GI tract synthesizes vitamins?
COLON in large intestines
75
What are the two neural components of large intestine motility? What are the subtypes of each (2 each)?
PNS = excitatory - Vagus n. = ascending colon, transverse colon - Pelvic n. = descending colon, sigmoid colon, rectum SNS = inhibitory - Superior and inferior mesenteric ganglions
76
With PNS neural component in large intestine, what are the two types and where does each act (2, 3)?
PNS = excitatory - Vagus n. = ascending colon, transverse colon - Pelvic n. = descending colon, sigmoid colon, rectum
77
What are the two types of motility in the large intestines?
- Haustration = mixing | - Mass movement (gastrocolic reflex)
78
What is the gastrocolic reflex and in what part of the GI tract is it used?
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
What portion of the GI tract involves longitudinal muscle separated by taeniae coli (3 bands); haustra?
Large intestines
80
Explain the process of defecation?
As rectal pressure increases, the rectal muscle contracts and IAS relaxes, EAS is contracted - When ready, EAS relaxes = BM
81
What enzyme breaks down complex sugars to oligosaccharides, and what are these five oligosaccharides?
AMYLASE - Lactose - Alpha-dextrins - Maltotriose - Maltose - Sucrose
82
Where are oligosaccharides broken down to simple sugars, and what are these three simple sugars?
At brush border - Glucose - Fructose - Galactose
83
What enzyme breaks down Lactose, and what two simple sugars is it broken down to?
Lactase - Glucose - Galactose
84
What two enzymes break down Alpha-dextrin, and what simple sugar is it broken down to?
Maltase and Alpha-dextrinase | - Glucose
85
What three enzymes break down Maltotriose, and what simple sugar is it broken down to?
Maltase, Sucrase, Alpha-dextrinase | - Glucose
86
What three enzymes break down Maltose, and what simple sugar is it broken down to?
Maltase, Sucrase, Alpha-dextrinase | - Glucose
87
What enzyme breaks down Sucrose, and what two simple sugars is it broken down to?
Sucrase - Glucose - Fructose
88
What simple sugar are most carbs digested into?
Glucose
89
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?
SGLT1 transport glucose and galactose | - Na-dependent
90
What transporter is found at the basolateral membrane to transport simple sugars/carbs, and which two carbs are transported here?
GLUT2 transports glucose/galactose
91
What two transporters are used to transport Fructose, and how does this occur?
DIFFUSION (not active) - GLUT5 on apical mem. - GLUT2 on basolateral mem.
92
What enzyme converts trypsinogen to trypsin, and what is the role of trypsin?
Enteropeptidase: trypsinogen → trypsin | - Trypsin activates inactive pancreatic enzymes in small intestine
93
Where are oligopeptides broken down, and what three things are they broken down to? What enzyme does this?
At brush border, oligosaccharides become... - AAs - Dipeptides - Tripeptides PERFORMED BY PEPTIDASES
94
What type of transport is used for AAs? What type of transport is used for dipeptides/tripeptides? How do these enter cells
- AAs = Na transport - Dipeptides/tripeptides = H+ transport All three enter cells via carriers
95
What enzyme converts TGs → FFAs?
Pancreatic Lipase
96
What enzyme converts cholesterolester → cholesterol?
Cholesterolester Hydrolase
97
What enzyme converts lecithin → lysolecithin?
Phospholipase A2
98
Three steps of fat transport/reabsorption?
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
How do Fat-Soluble vitamins differ from Water-Soluble vitamins in terms of transport?
- Fat-Soluble = processed like fats so micelles and chylomicrons - Water-soluble: Na-dependent transporters
100
Where does calcium absorption occur, and what can increase this? What is the role of this substance?
At Brush Border | - Increased CaBP → moves Ca2+ from apical membrane to basolateral membrane then out of cell (into blood)
101
Is more iron ingested or absorbed?
MORE INGESTED
102
What two proteins are involved in iron absorption, and what is the role of each?
- Transferrin = transport | - Ferritin = storage
103
How does water movement occur in the intestines?
Follows solutes/coupled to Na
104
What two substances are reabsorbed at the jejunum?
- Na | - HCO3
105
What two substances are reabsorbed at the ileum?
- Na | - Cl
106
What renal structure is the small intestine similar to? Large intestine?
- SI: proximal tubule | - LI: collecting duct
107
What two substances are reabsorbed by the large intestine, and how?
- Na via ENaC (induced by Aldosterone) | - K via diffusion

Physiology II (5 decks)

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