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Block 1 - GI > Phys 3-5 > Flashcards

Phys 3-5 Flashcards

1
Q

Role of GI secretions:

What 3 things do they do and how?

A
  1. Facilitate digestion (enzymes)
  2. Provide cell protection (mucous and neutralization of acid)
  3. Provide lubrication (mucous and serous fluid)
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2
Q

Locations of:

  1. Mucous cells
  2. Acinar cells
  3. Gastric gland cells
  4. Secretory cells
A
  1. Throughout the GI tract, mouth to large intestine
  2. Salivary glands and pancreas
  3. Wall of the stomach
  4. Mucosa of small intestine, Crypts of Lieberkühn
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3
Q

Neural: autonomic control of secretion

Parasympathetic vs. Sympathetic

A

P: increases secretion
S: decreases secretion by inhibiting parasympathetic ACh release and decreasing blood flow (alpha 1 vasoconstriction)

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4
Q

Secretion is usually mediated by which second messengers ?

A

Ca++
IP3
cAMP

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5
Q

A rise in ___ and ___ increases exocytosis

A

cAMP

Ca++

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6
Q

Mucins lubricate, and are made where?

A

Submandibular and

Sublingual glands

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7
Q

Salivary amylase does what?

Active pH range?

A

Breaks down starch to oligosaccharide molecules
4-11
7 is optimum

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8
Q

What does watery acinar secretion do?

A

Protects by buffering and diluting noxious substances

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9
Q

Absence of saliva due to lack or block or salivary gland

A

Xerostomia

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10
Q

The parotid gland is comprised of __
Submandibular?
Sublingual?

A

Only serous acini
*no mucous

The other two are mixed

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11
Q

Parasympathetic stimulation of salivary glands

A

Vasodilation
Increases blood flow
(ACh activates endothelial NO synthase and NO causes relaxation)

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12
Q

Saliva is always ___ to plasma

pH of secreted saliva:

A

Hypotonic

*higher flow rate=higher tonicity

8

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13
Q

Control of salivary secretion is ___

A

Neuronal - ANS only

Not hormonal

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14
Q

____ nerve ablation leads to atrophy of salivary glands but ___ ablation does not

A

Parasympathetic

Sympathetic

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15
Q

Characteristics unique to saliva:

A
  1. Always hypotonic
  2. Totally neural control
  3. Parasympathetic vasodilates
  4. Sympathetic causes secretion initially
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16
Q

Agents that induce an increase in ___ levels preferentially increase ___ secretion

A

cAMP

Amylase and mucous

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17
Q

___ cells secrete pepsinogen in the stomach
___ cells secrete HCl and intrinsic factor
___ cells secrete much of the mucous

A

Chief
Parietal
Neck

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18
Q

Potassium is always higher in the ___ than in the ___

A

Gastric acid
Plasma

*so vomiting may cause hypokalemia

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19
Q

Gastric juice contains:

A 
Salts
Water
Pepsins
Intrinsic factor
Mucous
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20
Q

Major anion of gastric acid?

___ converts pepsinogen to pepsin

A

Chloride

HCl

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21
Q

Mechanism of acid secretion

A

H+/K+ or proton pump
pH of secreted acid is 0.8!
K+ and Cl- are transported into the lumen
K+ is recycled

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22
Q

What is the “Alkaline Tide”?

A

Bicarbonate leaves the cell and enters the blood, raising the pH of venous blood leaving the stomach

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23
Q

Pepsinogen is secreted from ___ cells and is converted to pepsin at what pH?
What pH does it work best at?
What is it’s release stimulated by?

A

Chief
Less than 5
3 or below
-histamine, ACh, gastrin, secretin, CCK

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24
Q

What is the only gastric function required for life?

A

Secretion of intrinsic factor (which is a glycoproteins) by parietal cells

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25
Q

Intrinsic factor is required for___

A

Absorption of B12

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26
Q

Insoluble mucous for the barrier is secreted by ___

Soluble mucous is secreted by __

A

Surface epithelial cells

Pyloric glands

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27
Q

___ are known to increase mucosal blood flow as well as ___ and mucous secretion and to stimulate ___

A

Prostaglandins
Bicarbonate
Mucosal cell repair and renewal

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28
Q

What things inhibit normal mucous layer formation and reduce prostaglandin production. What can this lead to?

A
  • NSAIDs, alcohol, stress

- ulcers

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29
Q

Histamine is released from ___ cells and stimulates ___ receptors. It is blocked by ___

A

Enterochromaffin-like cells
H2
Cimetidine

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30
Q

ACh is released from ____ and stimulates ___ receptors. It is blocked by ___

A

Cholinergic nerves from Vagus
Muscarinic
Atropine

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31
Q

Gastrin is produced by ___ in the stomach antrum and duodenum.
What does it do?

A

G-cells

Stimulates acid release as ACh or Histamine

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32
Q

Any one agonist will potentiate the acid secretion elicited by another

A

Potentiation

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33
Q

3 sources of stimulation of gastric acid secretion

A
  1. Cephalic-sight or smell of food, chewing or swallowing
  2. Gastric-distension
  3. Intestinal-protein digestion products
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34
Q

Major mechanisms for inhibiting gastric acid secretion

A
  1. Acid in the antrum of the stomach
  2. Acid in the duodenum
  3. Hyperosmotic solutions, fatty acids, and monoglycerides on the duodenum
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35
Q

Most agents that increase HCl secretion also increase ____ secretion

But?

A

Pepsinogen

*But CCK and Secretin stimulate chief cells to secrete pepsinogen but inhibit HCl secretion

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36
Q

The pancreatic digestive enzymes are secreted by the acini into the pancreatic ducts and enter the duodenum via ___

A

Sphincter of Oddi

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37
Q

Pancreatic exocrine secretion control?

A

Neuronal and hormonal

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38
Q

Secretin elicits an ___ secretion of pancreatic juice while CCK elicits ___

A

Aqueous

Secretion rich in pancreatic enzymes

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39
Q

Pancreatic juice:

Aqueous part

A
  • Secreted by columnar epithelium lining the ducts
  • [Na] and [K] similar to plasma
  • HCO3 and Cl are the major anions
  • initially hypertonic, but then isotonic
  • secretin is the stimulus
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40
Q

Pancreatic juice:

Enzyme part

A
  • secreted by acinar cells
  • isotonic
  • Important for digestion of EVERYTHING
  • proteases (trypsinogen, chymotrypsinogen, procarboxypeptidase, ribonuclease, deoxyribonuclease)
  • contains amylase, trypsin inhibitor, and lipases
41
Q

Lipases included in pancreatic juices

A

Pancreatic lipase
Cholesterol ester hydrolase
Phospholipase A2

42
Q

The following are activated by what?
trypsinogen
chymotrypsinogen
Procarboxypeptidase

A

Enteropeptidase
Trypsin
Trypsin

43
Q

___ inhibits the activation of the proteases while in the pancreatic duct, thus preventing autodigestion of duct cells

A

Trypsin inhibitor

44
Q

Secretion of pancreatic juice control?

A

Neuronal and hormonal

45
Q

Functions and location of Brunner’s Glands

A

Submucosal

  • alkaline secretions neutralize acid
  • prevent peptic ulcers
46
Q

Functions of Crypts of Lieberkühn

A
  • isotonic alkaline secretion

- secrete Cl- and HCO3-

47
Q

Effects of cholera toxin on Crypts of Lieberkühn

A
  • Binds to brush border
  • Increased cAMP increases Cl- and HCO3- and water
  • Diarrhea
48
Q

Secretions of the Crypts of Lieberkühn in the large intestine are high in __

A

K+ and HCO3-

49
Q

This peptide is a pancreatic secretion which slows absorption

A

Pancreatic polypeptide

50
Q

This peptide is produced in the ileum

Inhibits gastric acid secretion and motility

A

Neurotensin

51
Q

This peptide inhibits gastric secretion and emptying in response to fat in the duodenum

A

Peptide YY

52
Q

This peptide stimulates motility of stomach and small intestine

A

Substance P

53
Q

Neurocrines

A
  • VIP
  • GRP-stimulates most secretions and gall bladder contraction, inhibits most other GI motility
  • Enkephalins-inhibit motility
54
Q

Paracrines

A
  • Somatostatin-released by D cells in the stomach; inhibits release of gastrin and histamine, thus inhibiting acid secretion
  • Histamine-stimulates acid secretion from parietal cells
55
Q

Hepatosplanchnic blood flow accounts for approximately ___% of the resting cardiac output (the most of any regional circulation)

A

25-30%

56
Q

Hepatosplanchnic circulation is arranged in series or parallel?

A

Both!
Arterial is in parallel
Venous is in series

57
Q

SMA vs IMA vs Celiac blood supply

A
  • SMA supplies upper intestine and pancreas
  • IMA supplies lower intestine and colon
  • Celiac supplies liver, stomach, and spleen
58
Q

The ___ accounts for about 70-75% of the total liver “in flow” of blood

A

Portal v.

*collects blood from other organs and transports it to the liver

59
Q

Hepatosplanchnic sympathetic control

A

Alpha 1 receptors: constriction of smooth muscle in arterioles, venules, and veins

60
Q

Hepatosplanchnic parasympathetic control

A
  • Increases secretion and motility

- secondarily increases production of vasoactive metabolites, which causes vasodilation

61
Q

Parasympathetic vasodilatory fibers are present in ___ glands

A

Salivary

62
Q

In response to a sudden increase in perfusion pressure ____ increases local vascular resistance to protect capillaries from the high pressure and excess fluid infiltration

A

Myogenic vasoconstriction

63
Q

Increases in secretory activity are closely linked to increases in ____ while increases in motor activity is linked to increases in ___

A

Mucosal blood flow

Muscularis blood flow

64
Q

Escape phenomenon

A

Sympathetic stimulation causes construction of arterioles and veins which results in a decrease in splanchnic blood flow
*despite continued stimulation, the splanchnic arterioles BUT NOT THE VEINS will spontaneously vasodilate (escape) within minutes

65
Q

Pathway of bile

A

Hepatic cells secrete bile into bile canaliculi–interlobular bile ducts–hepatic duct—common bile duct– duodenum (or gall bladder for storage via cystic duct)

66
Q

Primary bile acids
Formed from?
Examples?

A
  • from salts or newly synthesized by hepatocytes
  • cholic acid
  • chenodeoxycholic acid
67
Q

Secondary bile acids
Formed from?
Examples?

A
  • from the action of bacteria in the digestive tract
  • deoxycholic acid
  • lithocholic acid
68
Q

As the concentration of bile acids increases ___

A

They aggregate to form micelles

69
Q

Components of bile, in order of most to least prevalent

A 
Bile acids
Phospholipids 
Cholesterol
Bile pigments
Electrolytes
70
Q

This part of bile is not water soluble, becomes an important part of micelles, and is important in solubilizing cholesterol

A

Phospholipids

71
Q

T or F: bile pigments are not part of the micelles

A

True

72
Q

The bile duct epithelium secreted an aqueous solution that is high in ___ and low in ___. This process is stimulated by ___

A

HCO3-
Cl-
Secretin

73
Q

Vagal stimulation and CCK cause ___ of the gall bladder and ___ of the Sphincter of Oddi. CCK release is stimulated by ___

A

Contraction
Relaxation
Fats and partially digested protein in the duodenum

74
Q

Mechanism for absorption of water

A
  1. Na+/K+ ATPase moves Na+ into lateral intercellular spaces
  2. Cl- follows by facilitated transport
  3. Intercellular spaces become hypertonic
  4. Water enters by osmosis
  5. Hydrostatic pressure moves water into capillaries
75
Q

All bile acids are transported away from the intestine in ___ bound to ___

A

Portal blood

Plasma proteins

76
Q

Tight junctions of intestinal epithelial cells are most “leaky” where?

A

Duodenum and they get tighter as you move down

77
Q

Passage for ions and water through tight junctions in the intestinal epithelium and lateral intracellular spaces
Vs.
transport through the cells
**which one contributes more to ion conductance of the mucosa?

A

**Paracellular transport

Transcellular transport

78
Q

Net flux of water and ions is from the ___ to the ___

A

GI lumen to the blood

79
Q

Little net absorption of water occurs in the ___, most occurs in the ___, and some occurs in the ___

A

Duodenum
Jejunum
Colon

80
Q

In which part of the intestines is Na+ absorbed?
Up or down it’s electrochemical gradient?
Net rate of absorption is highest where?

A

Entire length
down
Jejunum

81
Q

Chloride and bicarbonate ions are absorbed in large amounts in the ___. In the ___ chloride continues to be reabsorbed but bicarbonate is normally secreted. Why?

A

Jejunum
Ileum and colon
-Brush border exchange protein that is not found in the jejunum

82
Q

Net flux of K+ is from the ___ to the ___

A

Lumen to the blood in the jejunum and ileum

83
Q

What is a big concern with diarrhea?

A

Hypokalemia

84
Q

T or F: Ca++ is only absorbed in the duodenum

A

False

All segments of the intestine but esp. Duodenum and jejunum

85
Q

IMCal

A

Intestinal membrane calcium binding protein

-binds Ca at the brush border membrane

86
Q

CaBP

A

Or Calbindin
Calcium binding protein
Binds two Ca ions, essential for Ca absorption

87
Q

Where can you find 2 transport proteins that can extrude Ca from the cell?

A

Basolateral membrane

88
Q

Stomach and intestine motility and tone

  1. Sympathetic receptor type
  2. Sympathetic influence
  3. Parasympathetic influence
A
  1. Alpha 2
  2. Decrease
  3. Increase
89
Q

Sphincters

  1. Sympathetic receptor type
  2. Sympathetic influence
  3. Parasympathetic influence
A
  1. Alpha 1
  2. Contract
  3. Relax
90
Q

Secretion

  1. Sympathetic receptor type
  2. Sympathetic influence
  3. Parasympathetic influence
A
  1. Alpha 2
  2. Inhibit
  3. Stimulate
91
Q

Gall bladder and ducts

  1. Sympathetic receptor type
  2. Sympathetic influence
  3. Parasympathetic influence
A
  1. /
  2. Relaxation
  3. Contraction
92
Q

Pancreas Acini

  1. Sympathetic receptor type
  2. Sympathetic influence
  3. Parasympathetic influence
A
  1. Alpha 2
  2. Decreased enzyme secretion
  3. Increased enzyme secretion
93
Q

Salivary glands

  1. Sympathetic receptor type
  2. Sympathetic influence
  3. Parasympathetic influence
A
  1. Alpha 1
  2. Scant viscous secretion
  3. Profuse watery secretion
  4. Beta 2
  5. Amylase secretion
94
Q

gastrin

  1. Stimulus for release
  2. Target organ
  3. Effects on motility
  4. Effects on secretion
A
  1. Sight, smell, chewing food (vagal)
    - stomach stretch, proteins in duodenum
  2. Stomach
  3. Increase
  4. Pepsinogen and HCl
95
Q

Secretin

  1. Stimulus for release
  2. Target organ
  3. Effects on motility
  4. Effects on secretion
A
  1. Acid in S.I.
  2. Stomach and pancreas
  3. Decrease
  4. Increase Pepsinogen , block HCl
96
Q

CCK

  1. Stimulus for release
  2. Target organ
  3. Effects on motility
  4. Effects on secretion
A
  1. Fat or small proteins in S.I.
    - Stomach (decrease motility, block HCl, increase pepsinogen)
    - gall bladder (increase motility)
    - sphincter of Oddi (relaxed)
    - Pancreas (enzyme secretin increases)
97
Q

GIP

  1. Stimulus for release
  2. Target organ
  3. Effects on motility
  4. Effects on secretion
A
  1. Fat in S.I.
  2. Stomach
  3. Decrease
  4. Block HCl
98
Q

Motilin

  1. Stimulus for release
  2. Target organ
  3. Effects on motility
  4. Effects on secretion
A
  1. Cyclic/2hrs inhibited by digestion
  2. Stomach and S.I.
  3. Increase
  4. /

Block 1 - GI (15 decks)

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