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Physiology Exam 3 > Lecture 5: Gastric, Pancreatic, Bile Secretions > Flashcards

Lecture 5: Gastric, Pancreatic, Bile Secretions Flashcards

1
Q

What are the direct paths of vagal stimulation?

A

Vagus nerve -> Parietal cells -> ACh -> HCl
Vagus nerve -> GRP -> G Cells

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2
Q

What are the indirect paths of vagal stimulation

A

Rest of G cell path
Gastrin from G cells -> Systemic circulation -> HCl from parietal cells

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3
Q

Which pathway will atropine block?

A

Vagus nerve -> Parietal cells -> ACh -> HCl

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4
Q

Why will atrophne not block HCl secretion completely?

A

Only affecting 1 of 3 pathways

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5
Q

Name the phases of gastric HCl secretion

A

Cephalic, gastric, intestinal

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6
Q

Which phase accounts for 30% of total HCl?

A

Cephalic

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7
Q

Which phase accounts for 60% of total HCl?

A

Gastric

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8
Q

Which phase accounts for 10% of total HCl?

A

Intestinal

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9
Q

What are stimuli for the cephalic phase?

A

Smelling, tasting, chewing, swallowing, conditioned reflexes

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10
Q

What are the mechanisms to promote HCl secretion in the cephalic phase?

A

Direct stimulation of parietal cells by vagus nerve
Indirect stimulation via gastrin

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11
Q

What are the stimuli for the gastric phase?

A

Distention of stomach and presence of AA and peptides

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12
Q

What are the mechanisms to promote HCl secretion in gastric phase?

A
  1. Distention -> Vagal nerve stimulation -> Parietal cells
  2. Indirect via gastrin
  3. Distention of antrum -> Local reflexes -> Gastrin release
  4. AA + Peptides -> G cells -> Gastrin
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13
Q

What is the intestinal phase stimulated by?

A

Products of protein digestion

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14
Q

What is the intestinal phase stimulated by?

A

Products of protein digestion

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15
Q

When is HCl secretion inhibited (why is it no longer needed)

A

No longer needed for conversion of pepsinogen to pepsin

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16
Q

Decreased what of gastric contents inhibits HCl secretion?

A

pH

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17
Q

How does somatostatin directly inhibit HCl secretion?

A

Binds parietal cells and antagonizes histamine pathway by decreasing cAMP

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18
Q

How does somatostatin indirectly inhibit HCl secretion?

A

Inhibits both histamine and gastrin release

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19
Q

How do prostaglandins antagonize histamine in the inhibition of HCl secretion?

A

Reducing cAMP

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20
Q

What are the barriers to acid and pepsin damage to gastric mucosa?

A

Bicarbonate and mucus

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21
Q

What is peptic ulcer disease?

A

Ulcerative lesion of gastric or duodenal mucosa

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22
Q

Name the causes of peptic ulcer disease

A

Could be 1 or both:
Loss of mucus
Excessive H+ and pepsin secretion

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23
Q

Why do gastric ulcers form?

A

Because mucosal barrier is defective, so H+ and pepsin digest mucosa

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24
Q

Why do duodenal ulcers form?

A

Occur when H+ secretory rate higher than normal, overwhelm buffering capacity of pancreas

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25
What is the SNS innervation of the exocrine pancreas?
Celiac and superior mesenteric plexuses
26
What is the PNS innervation of the exocrine pancreas?
Vagal nerve
27
What effect does PSNS stimulation have on exocrine pancreas?
Stimulates secretion
28
What effect does SNS stimulation have on exocrine pancreas?
Inhibits secretions
29
Name the two components of pancreatic secretions
Enzymatic component Aqueous component
30
What is the enzymatic component of pancreatic secretions responsible for digesting?
Carbs, proteins, lipids
31
Where are the enzymes of pancreatic secretion synthesized?
Rough ER of acinar cells
32
Where are the enzymes of pancreatic secretion stored?
On zymogens
33
What form are amylase and lipases secreted by pancreas?
Active
34
What form are proteases secreted by pancreas?
Inactive (known as zymogens)
35
Pancreatic juice is ______
Isotonic
36
What does pancreatic juice contain
Na, Cl, K, HCO3
37
What cell produces initial aqueous component of pancreas secretion?
Centroacinar and ductal cells
38
What cell modifies the secretion of pancreatic juice?
Ductal cells
39
For pancreatic secretions, where does HCO3 go, and where does H+ go?
HCO3 goes to lumen H+ goes to blood
40
What transports are on the luminal membrane?
HCO3/Cl exchanger
41
What transports are on the basolateral membrane?
Na/K ATPase Na/K Exchanger
42
How do Na+ and K+ concentrations in pancreatic juice compare to plasma?
Similar
43
The concentrations of Cl and HCO3 of pancreatic juice...
Vary with flow rate
44
T/F: The concentrations of Na+ and K+ in plasma vary with flow rate
False
45
At high flow rates HCO3 concentration
Increases
46
At low flow rates HCO3 concentration
Decreases
47
At high flow rates Cl concentration
Decreases
48
At low flow rates Cl concentration
Increases
49
At high flow rates, what does pancreatic juice mostly contain?
Na, HCO3, water
50
At low flow rates, what does pancreatic juice mostly contain?
Na, Cl, water
51
What is aqueous portion of pancreatic secretion stimulated by?
H+ in duodenum (will need bicarb)
52
What is the enzymatic portion of pancreatic secretions stimulated by?
Products of digestion
53
Gastric phase accounts for what % of secretions?
80%
54
Acinar cells contain receptors for what
CCK and ACh (muscarinic)
55
H+ stimulates which cells to release what?
S cells to release secretin
56
AA and peptides stimulate secretion of what?
CCK
57
What potentiates action of CCK?
ACh
58
Describe the pathway for aqueous secretion in pancreatic juice
H+ > S cells > Secretin > cAMP on ductal cells (Ach and CCK potentiate) > Secretion
59
Describe the pathway for enzymatic secretion in pancreatic juice
Small peptides + fatty acids > I cells > CCK > IP3, Ca2+ (Ach potentiates) > Enzymes
60
Ductal cells have receptors for what
CCK, ACh, Secretin
61
Stimulation of ductal cell receptors stimulates
Bicarb for aqueous portion of pancreatic juice
62
Mixture of bile salts, bile pigments, cholesterol, phospholipids, ions, water
Bile
63
Emulsify lipids to prepare for digestion, then solubilizes products into micelles for absorption
Bile salts
64
What is contained in the biliary system?
Liver, gallbladder, bile duct, duodenum, ileum, portal circulation
65
What synthesize components of liver bile?
Hepatocytes
66
What does CCK do in biliary system?
Stimulates contraction of gallbladder Relaxes sphincter of Oddi
67
What happens to bile salts after lipid absorption?
Recirculated to liver via reabsorption in ileum
68
What is the composition of bile?
Bile salts, bile pigments, cholesterol, phospholipids, ions, water
69
What is 50% of the composition of bile?
Bile salts
70
What is 40% of the composition of bile?
Phospholipids
71
What does liver conjugate to form bile salts?
Bile acids and AA (glycine and taurine)
72
What are the two primary bile acids made by hepatocytes?
Colic acid and chenodeoxycholic acid
73
What is the responsibility of bile acids?
Emulsify lipids so digestion can occur
74
T/F: Bile acids are amphipathic
True
75
Bile salts bind to form
Micelles
76
What does the core of a micelle contain?
Products of digestion
77
What two things equal a micelle?
Finely emulsified fat + bile salts
78
What is the product of hemoglobin degradation?
Bilirubin
79
What are the functions of the gallbladder?
Stores, concentrates, ejects bile Filling of gallbladder Concentration of bile Ejection of bile
80
Is bile produced continuously or periodically?
Continuously
81
Bile ejection occurs how long after meal ingested
30 minutes
82
CCK contacts and relaxes what for bile ejection
Contracts gallbladder Relaxes sphincter of Oddi
83
Bile is ejected in
Spurts
84
Enterohepatic circulation
How most bile salts return to the liver
85
What are bile salts transported from ileum lumen to portal blood by?
Na+/bile salt co-transporters

Physiology Exam 3 (13 decks)

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