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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
Intrinsic factor is required for___
Absorption of B12
26
Insoluble mucous for the barrier is secreted by ___ | Soluble mucous is secreted by __
Surface epithelial cells | Pyloric glands
27
___ are known to increase mucosal blood flow as well as ___ and mucous secretion and to stimulate ___
Prostaglandins Bicarbonate Mucosal cell repair and renewal
28
What things inhibit normal mucous layer formation and reduce prostaglandin production. What can this lead to?
- NSAIDs, alcohol, stress | - ulcers
29
Histamine is released from ___ cells and stimulates ___ receptors. It is blocked by ___
Enterochromaffin-like cells H2 Cimetidine
30
ACh is released from ____ and stimulates ___ receptors. It is blocked by ___
Cholinergic nerves from Vagus Muscarinic Atropine
31
Gastrin is produced by ___ in the stomach antrum and duodenum. What does it do?
G-cells | Stimulates acid release as ACh or Histamine
32
Any one agonist will potentiate the acid secretion elicited by another
Potentiation
33
3 sources of stimulation of gastric acid secretion
1. Cephalic-sight or smell of food, chewing or swallowing 2. Gastric-distension 3. Intestinal-protein digestion products
34
Major mechanisms for inhibiting gastric acid secretion
1. Acid in the antrum of the stomach 2. Acid in the duodenum 3. Hyperosmotic solutions, fatty acids, and monoglycerides on the duodenum
35
Most agents that increase HCl secretion also increase ____ secretion But?
Pepsinogen *But CCK and Secretin stimulate chief cells to secrete pepsinogen but inhibit HCl secretion
36
The pancreatic digestive enzymes are secreted by the acini into the pancreatic ducts and enter the duodenum via ___
Sphincter of Oddi
37
Pancreatic exocrine secretion control?
Neuronal and hormonal
38
Secretin elicits an ___ secretion of pancreatic juice while CCK elicits ___
Aqueous | Secretion rich in pancreatic enzymes
39
Pancreatic juice: | Aqueous part
- 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
40
Pancreatic juice: | Enzyme part
- secreted by acinar cells - isotonic - Important for digestion of EVERYTHING - proteases (trypsinogen, chymotrypsinogen, procarboxypeptidase, ribonuclease, deoxyribonuclease) - contains amylase, trypsin inhibitor, and lipases
41
Lipases included in pancreatic juices
Pancreatic lipase Cholesterol ester hydrolase Phospholipase A2
42
The following are activated by what? trypsinogen chymotrypsinogen Procarboxypeptidase
Enteropeptidase Trypsin Trypsin
43
___ inhibits the activation of the proteases while in the pancreatic duct, thus preventing autodigestion of duct cells
Trypsin inhibitor
44
Secretion of pancreatic juice control?
Neuronal and hormonal
45
Functions and location of Brunner's Glands
Submucosal - alkaline secretions neutralize acid - prevent peptic ulcers
46
Functions of Crypts of Lieberkühn
- isotonic alkaline secretion | - secrete Cl- and HCO3-
47
Effects of cholera toxin on Crypts of Lieberkühn
- Binds to brush border - Increased cAMP increases Cl- and HCO3- and water - Diarrhea
48
Secretions of the Crypts of Lieberkühn in the large intestine are high in __
K+ and HCO3-
49
This peptide is a pancreatic secretion which slows absorption
Pancreatic polypeptide
50
This peptide is produced in the ileum | Inhibits gastric acid secretion and motility
Neurotensin
51
This peptide inhibits gastric secretion and emptying in response to fat in the duodenum
Peptide YY
52
This peptide stimulates motility of stomach and small intestine
Substance P
53
Neurocrines
- VIP - GRP-stimulates most secretions and gall bladder contraction, inhibits most other GI motility - Enkephalins-inhibit motility
54
Paracrines
- 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
Hepatosplanchnic blood flow accounts for approximately ___% of the resting cardiac output (the most of any regional circulation)
25-30%
56
Hepatosplanchnic circulation is arranged in series or parallel?
Both! Arterial is in parallel Venous is in series
57
SMA vs IMA vs Celiac blood supply
- SMA supplies upper intestine and pancreas - IMA supplies lower intestine and colon - Celiac supplies liver, stomach, and spleen
58
The ___ accounts for about 70-75% of the total liver "in flow" of blood
Portal v. | *collects blood from other organs and transports it to the liver
59
Hepatosplanchnic sympathetic control
Alpha 1 receptors: constriction of smooth muscle in arterioles, venules, and veins
60
Hepatosplanchnic parasympathetic control
- Increases secretion and motility | - secondarily increases production of vasoactive metabolites, which causes vasodilation
61
Parasympathetic vasodilatory fibers are present in ___ glands
Salivary
62
In response to a sudden increase in perfusion pressure ____ increases local vascular resistance to protect capillaries from the high pressure and excess fluid infiltration
Myogenic vasoconstriction
63
Increases in secretory activity are closely linked to increases in ____ while increases in motor activity is linked to increases in ___
Mucosal blood flow | Muscularis blood flow
64
Escape phenomenon
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
Pathway of bile
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
Primary bile acids Formed from? Examples?
- from salts or newly synthesized by hepatocytes - cholic acid - chenodeoxycholic acid
67
Secondary bile acids Formed from? Examples?
- from the action of bacteria in the digestive tract - deoxycholic acid - lithocholic acid
68
As the concentration of bile acids increases ___
They aggregate to form micelles
69
Components of bile, in order of most to least prevalent
``` Bile acids Phospholipids Cholesterol Bile pigments Electrolytes ```
70
This part of bile is not water soluble, becomes an important part of micelles, and is important in solubilizing cholesterol
Phospholipids
71
T or F: bile pigments are not part of the micelles
True
72
The bile duct epithelium secreted an aqueous solution that is high in ___ and low in ___. This process is stimulated by ___
HCO3- Cl- Secretin
73
Vagal stimulation and CCK cause ___ of the gall bladder and ___ of the Sphincter of Oddi. CCK release is stimulated by ___
Contraction Relaxation Fats and partially digested protein in the duodenum
74
Mechanism for absorption of water
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
All bile acids are transported away from the intestine in ___ bound to ___
Portal blood | Plasma proteins
76
Tight junctions of intestinal epithelial cells are most "leaky" where?
Duodenum and they get tighter as you move down
77
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?
**Paracellular transport | Transcellular transport
78
Net flux of water and ions is from the ___ to the ___
GI lumen to the blood
79
Little net absorption of water occurs in the ___, most occurs in the ___, and some occurs in the ___
Duodenum Jejunum Colon
80
In which part of the intestines is Na+ absorbed? Up or down it's electrochemical gradient? Net rate of absorption is highest where?
Entire length down Jejunum
81
Chloride and bicarbonate ions are absorbed in large amounts in the ___. In the ___ chloride continues to be reabsorbed but bicarbonate is normally secreted. Why?
Jejunum Ileum and colon -Brush border exchange protein that is not found in the jejunum
82
Net flux of K+ is from the ___ to the ___
Lumen to the blood in the jejunum and ileum
83
What is a big concern with diarrhea?
Hypokalemia
84
T or F: Ca++ is only absorbed in the duodenum
False | All segments of the intestine but esp. Duodenum and jejunum
85
IMCal
Intestinal membrane calcium binding protein | -binds Ca at the brush border membrane
86
CaBP
Or Calbindin Calcium binding protein Binds two Ca ions, essential for Ca absorption
87
Where can you find 2 transport proteins that can extrude Ca from the cell?
Basolateral membrane
88
Stomach and intestine motility and tone 1. Sympathetic receptor type 2. Sympathetic influence 3. Parasympathetic influence
1. Alpha 2 2. Decrease 3. Increase
89
Sphincters 1. Sympathetic receptor type 2. Sympathetic influence 3. Parasympathetic influence
1. Alpha 1 2. Contract 3. Relax
90
Secretion 1. Sympathetic receptor type 2. Sympathetic influence 3. Parasympathetic influence
1. Alpha 2 2. Inhibit 3. Stimulate
91
Gall bladder and ducts 1. Sympathetic receptor type 2. Sympathetic influence 3. Parasympathetic influence
1. / 2. Relaxation 3. Contraction
92
Pancreas Acini 1. Sympathetic receptor type 2. Sympathetic influence 3. Parasympathetic influence
1. Alpha 2 2. Decreased enzyme secretion 3. Increased enzyme secretion
93
Salivary glands 1. Sympathetic receptor type 2. Sympathetic influence 3. Parasympathetic influence
1. Alpha 1 2. Scant viscous secretion 3. Profuse watery secretion 1. Beta 2 2. Amylase secretion
94
gastrin 1. Stimulus for release 2. Target organ 3. Effects on motility 4. Effects on secretion
1. Sight, smell, chewing food (vagal) - stomach stretch, proteins in duodenum 2. Stomach 3. Increase 4. Pepsinogen and HCl
95
Secretin 1. Stimulus for release 2. Target organ 3. Effects on motility 4. Effects on secretion
1. Acid in S.I. 2. Stomach and pancreas 3. Decrease 4. Increase Pepsinogen , block HCl
96
CCK 1. Stimulus for release 2. Target organ 3. Effects on motility 4. Effects on secretion
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
GIP 1. Stimulus for release 2. Target organ 3. Effects on motility 4. Effects on secretion
1. Fat in S.I. 2. Stomach 3. Decrease 4. Block HCl
98
Motilin 1. Stimulus for release 2. Target organ 3. Effects on motility 4. Effects on secretion
1. Cyclic/2hrs inhibited by digestion 2. Stomach and S.I. 3. Increase 4. /

Block 1 - GI (15 decks)

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