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PHPY 303 > 03- Gastrointestinal > Flashcards

03- Gastrointestinal Flashcards

1
Q

What is the fundamental role of the GI tract?

A

Extract nutrients from the external environment to provide energy and building blocks

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2
Q

What are the four functions of the GI tract?

A

Digestion, absorption, secretion, and motility

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3
Q

What is receptive relaxation?

A

Making space in the stomach in response to swallowing

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4
Q

What is gastrica ccomodation?

A

The vagovagal reflex triggers further relaxation in the stomach

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5
Q

What are the three phases of acid secretion in the stomach?

A

Cephalic, gastric, and intestinal

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6
Q

What is the postprandial phase?

A

Digestion period after eating

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7
Q

What is the interdigestive phase?

A

The period where we are not fed or digestion is complete

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8
Q

How small must food be to pass through the pyloric sphincter in the various phases?

A

Less than 2mm during the postprandial phase

More than 2mm in the interdigestive phase

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9
Q

What moves material through the small intestine during the interdigestive phase?

A

The migrating motor complex

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10
Q

Which nerve innervates the majority of the GI tract?

A

The vagus nerve

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11
Q

Which nerve innervates the distal colon?

A

The pelvic nerve

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12
Q

What does calcium do in the body?

A

Modulates hormone secretion, muscle contraction, nerve conduction, exocytosis, and the activity of many metabolic enzymes

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13
Q

What does phosphate do in the body?

A

Acts as a key component in ATP

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14
Q

How do calcium and phosphate regulation coordinate?

A

Together they are the principal components of hydroxyapatite crystals (mineral component of bone) and they are regulated by the same hormone

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15
Q

What is parathyroid hormone?

A

A peptide hormone synthesized and stored in the parathyroid glands

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16
Q

What does parathyroid hormone do?

A

Promotes Ca reabsorption and inhibits PO4 reabsorption

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17
Q

How do calcium levels influence PTH?

A

PTH synthesis is inhibited by high Ca and activated by low Ca

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18
Q

What does vitamin D do?

A

Binds to nuclear receptors to suppress PTH production

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19
Q

How does excess PO4 influence PTH?

A

PTH levels rise to balance the Ca-PO4 ratio

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20
Q

What do epithelial cells secrete?

A

Bicarbonate and mucus

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21
Q

What do parietal cells secrete?

A

HCl

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22
Q

What do chief cells secrete?

A

Pepsinogen and gastric lipase

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23
Q

What cells are in the corpus and what do they secrete?

A

Enterochromaffin-like cells secrete histamine

D cells secrete somatostatin

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24
Q

What cells are in the antrum and what do they secrete?

A

G cells secrete gastrin

D cells secrete somatostatin

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25
Q

What does the low pH of the stomach do to proteins?

A

Causes their denaturation to expose proteolytic sites

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26
Q

What two pH values are important for pepsinogen?

A

Pepsinogen is cleaved at a pH of 3.5 and activated at a pH of 3

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27
Q

Why do H and Cl move to the lumen?

A

H is exchanged for K which enters due to a concentration gradient
Cl follows a concentration gradient

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28
Q

How is the stomach protected from the low pH and pepsin?

A

Epithelial cells secreting bicarbonate and mucins

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29
Q

How does acetylcholine increase gastric acid secretion?

A

It stimulates histamine release which acts on histamine receptors, gastrin release which acts on CCK receptors, and the acetylcholine acts directly on M3 receptors

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30
Q

What factors stimulate acid secretion in the intestinal phase?

A

Gastrin, entero-oxyntin, and absorbed amino acids

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31
Q

How does somatostatin cause negative feedback?

A

Inhibition of histamine, gastrin, and acid secretion

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32
Q

What are the basic functions of salivary exocrine glands?

A

Lubricate ingested food, initiate starch digestion, and prevent dehydration of oral mucosa

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33
Q

What are the basic functions of pancreatic exocrine glands?

A

Produce a pancreatic juice that neutralizes chyme as it enters the duodenum and is rich in zymogens which facilitate digestion

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34
Q

What are acinar cells?

A

Polarized epithelial cells specialized for the production and export of protein

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35
Q

What are duct cells?

A

Polarized epithelial cells specialized for the export of electrolytes

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36
Q

What is the primary function of duct cells?

A

Fluid and electrolyte transport

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37
Q

What do serous-type acinar cells secrete?

A

Amylase

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38
Q

What do mucous-type acinar cells secrete?

A

Mucin and proline-rich proteins

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39
Q

What is sjorgen syndrome?

A

An autoimmune disease that can destroy salivary glands

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40
Q

What controls salivary secretions?

A

The parasympathetic nervous system

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41
Q

What do bicarbonate and isotonic fluid secreted from the duct cells do in the duodenum?

A

Provide hydration to the mucous layer and neutralize the pH

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42
Q

What prevents premature activation of zymogens?

A

Enterokinase is only found in the duodenum, zymogens are condensed in granules, and inhibitors of digestive enzymes are co-packed in the secretory granules

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43
Q

What absorption occurs in the small intestine?

A

Nutrients, Na, K, Cl, and water

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44
Q

What absorption occurs in the large intestine?

A

Electrolytes and water

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45
Q

What cells cause absorption in the large and small intestine?

A

Villous absorptive cells in the small intestine

Surface absorptive cells in the large intestine

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46
Q

What cells perform secretion?

A

Crypt cells

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47
Q

Why are tight junctions important?

A

Prevention of unwanted material in the intestinal lumen from entering

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48
Q

What is solvent drag?

A

When fluid movement takes ions with it

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49
Q

What is the most significant contributor to Na absorption in the post-prandial phase?

A

Na/glucose or Na/amino acid cotransporters

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50
Q

What is the main function of the Na/H exchanger?

A

Neutralize pH when it becomes too high

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51
Q

What is the primary mechanism of Na absorption between meals?

A

Na/H and Cl/HCO3 coexchanger

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52
Q

How do epithelial Na channels work?

A

Na moves down its concentraton gradient

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53
Q

How does passive Cl absorption work?

A

Cl moves down its electrochemical gradient in a paracellular or transcellular method

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54
Q

What is unique about the Cl/HCO3 coexchanger when discussing chloride movement?

A

It works independent of the Na/H coexchanger

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55
Q

What is the primary mechanism of Cl absorption between meals?

A

Na/H and Cl/HCO3 exchanger

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56
Q

Where does Cl secretion occur?

A

In the large and small intestine via crypt cells

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57
Q

Where and how does passive K absorption occur?

A

In the small intestine via solvent drag

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58
Q

Where and how does active K absorption occur?

A

The distal end of the colon in exchange for a hydrogen

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59
Q

Where and how does passive K secretion occur?

A

Occurs in the large intestine via solvent drag

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60
Q

What can stimulate secretion?

A

Secretagogues such as the enteric nervous system and immune cells

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61
Q

What can stimulate absorption?

A

Aldosterone, angiotensin, and somatostatin

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62
Q

Where are macronutrients absorbed?

A

The duodenum and jejunum

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63
Q

Where are iron and folate absorbed?

A

Duodenum

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64
Q

Where is calcium absorbed?

A

Throughout the small intestine

65
Q

Where are bile acids absorbed?

A

Distal jejunum, ileum, and ascending colon

66
Q

Where is B12 absorbed?

A

Ileum

67
Q

What does amylase do in digestion?

A

Reduces polysaccharides to oligosaccharides

68
Q

What do brush border enzymes do in carbohydrate digestion?

A

Digest oligosaccharides into monosaccharides

69
Q

What is lactase?

A

The only enzyme which can digest lactose

70
Q

What can maltase, sucrase, and isomaltase all digest?

A

Alpha1-4 linkages of maltose, maltotriose, and alpha-limit dextrins

71
Q

What can maltase digest?

A

Straight chain oligosaccharides 9 monomers long

72
Q

What can sucrase digest?

A

Sucrose

73
Q

What can isomaltase digest?

A

Alpha1-6 linkages

74
Q

How is the absorption of glucose and galactose mediated on the apical surface?

A

Sodium-glucose co-transporter

75
Q

What mediates the absorption of fructose on the apical surface?

A

Glut5

76
Q

What mediates the transport of monosaccharides into the blood stream on the basolateral surface?

A

Glut2

77
Q

What causes lactose intolerance?

A

Lactase deficiency

78
Q

What causes glucose-galactose malabsorption?

A

SGLT1 deficiency

79
Q

What reduces proteins into oligopeptides?

A

Pepsin and pancreatic proteases

80
Q

What breaks oligopeptides into absorbable sizes?

A

Brush border peptidases

81
Q

How are amino acids in the intestinal lumen absorbed?

A

Sodium/amino acid co-transporter

82
Q

How are tetra, tri, and di-peptides absorbed?

A

H/oligopeptide co-transporter called PepT1

83
Q

When does hartnup disease occur?

A

Absorption of neutral amino acids is defective

84
Q

When does cystinuria occur?

A

When absorption of cationic amino acids is defecctive

85
Q

When does lysinuric protein intolerance occur?

A

When there is impaired basolateral transport of cationic amino acids

86
Q

What is key to lipid digestion?

A

Emulsification in the duodenum to form a microenvironment in which digested lipids become accessible

87
Q

What makes up mixed micelles?

A

Bile salts, fatty acids, monoacylglycerols, lysophospolipids, and cholesterol

88
Q

Which proteins mediate fatty acid uptake?

A

Fatty acid translocase, intestinal fatty acid binding protein, and fatty acid transport protein

89
Q

What happens if bile acids are absorbed?

A

They are secreted into the lumen using ABCG1/ABCG8 transporter

90
Q

How is cholesterol absorption mediated?

A

Niemann-pick C-1 like 1 protein

91
Q

What happens to lipids once they have been absorbed?

A

They are packaged into chylomicrons and enter the lymphatic system

92
Q

How is folate absorbed?

A

PteGlu7 is deconjugated by folate conjugase which converts it to PteGlu1. This is absorbed by SLC46A1

93
Q

How is cobalamin absorbed?

A

It binds to intrinsic factor and is carried into enterocytes through receptor mediated uptake

94
Q

How is non-heme iron absorbed?

A

Ferric iron is converted to ferrous iron by ferric reductase Dcytb, and then ferrous iron is absorbed via the divalent metal co-transporter DMT1

95
Q

What are the functions of the liver?

A

Enhance lipid absorption, detoxify compounds, produce substances, and store, metabolize, and distribute nutrients

96
Q

What side of hepatocytes are microvilli present on?

A

Basolateral

97
Q

Which side of hepatocytes are canaliculi on?

A

Apical

98
Q

Where does the blood flowing through the liver come from?

A

75% portal vein, 25% hepatic artery

99
Q

What makes up the portal triad?

A

Hepatic artery, portal vein, and bile duct

100
Q

What are the main primary bile acids present in humans?

A

Cholic acid and chenodeoxycholic acid

101
Q

What is used to uptake bile salts?

A

Sodium/taurocholate cotransporting polypeptide

102
Q

What is the main exporter of bile acids?

A

Bile salt export protein

103
Q

What mediates conjugated bilirubin uptake?

A

OATP1B1 and OATP1B3

104
Q

What mediates the uptake and excretion of organic cations?

A

Uptake occurs via the organic cation transporter and excretion occurs via MDR1

105
Q

What is the major component of bile?

A

Phosphatidylcholine

106
Q

What occurs in phase one of hepatocyte detoxification?

A

Oxidation-reduction reactions performed by cytochrome p450 enzymes to make the compound more polar

107
Q

What occurs in phase two of hepatocyte detoxification?

A

Conjugation with agents such as sulfate, glucuronate, or glutathione to make the compound more water soluble.

108
Q

What occurs in phase three of hepatocyte detoxification?

A

Modified compound is recognized and delivered to transporters for excretion

109
Q

What is canalicular bile flow?

A

The sum of a constant bile acid independent flow, and a flow that is dependent on the amount of bile being excreted

110
Q

What is total bile flow?

A

The sum of canalicular bile flow and ductular secretions from cholangiocytes

111
Q

What is the second major source of fluid in bile?

A

Cholangiocytes

112
Q

What stimulates gallbladder emptying?

A

CCK secreted from I cells

113
Q

What provides negative feedback to the gallbladder?

A

Fibroblast growth factor 19 which is secreted when bile reaches the ileum

114
Q

What does the sphincter of oddi do?

A

Controls bile flow

115
Q

What are the mechanisms of bile recycling?

A

Passive intestinal absorption, active intestinal absorption, feedback via FGF19, and hepatic regulation

116
Q

What does microsomal triglyceride transfer protein do?

A

Catalyzes the lipidation of apolipoprotein B-48 and the lipid droplet

117
Q

What is a lacteal?

A

A single, blind-ended, lymphatic vessel at the centre of each intestinal villus

118
Q

What are lipoproteins?

A

Structures of lipids and proteins used to transport lipids through the body

119
Q

What does GPIHBP1 do?

A

Tethers the lipoprotein to the lipase to encourage breakdown

120
Q

Where does the liver get cholesterol?

A

Chylomicron remnant, LDL, HDL remnant, and synthesis

121
Q

Where does cholesterol from the liver get sent?

A

Bile acids, direct secretion, and out in VLDL

122
Q

What is TG-CE exchange?

A

HDL gives other lipoproteins cholesterol ester in exchange for TAG

123
Q

What are VLDLs made of?

A

TAG. phospholipids, cholesterol, cholesterol esters, and proteins

124
Q

Where do triacylglycerol’s in the liver come from?

A

Fatty acid flux, de novo lipogenesis, and liver stores

125
Q

Where does the liver send TAGs?

A

VLDL synthesis and secretion, oxidation, and liver stores

126
Q

What exchange occurs between the liver and the muscle?

A

Liver produces glucose and ketone bodies

Muscle provides lactate and amino acids

127
Q

How does adipose tissue regulate the liver?

A

Liver metabolism is regulated by adipokines and hormones secreted from the adipose tissue

128
Q

What characteristics do white adipocytes have?

A

They are spherical, contain a single lipid droplet, and expand for larger lipid storage capacity

129
Q

What characteristics do brown adipocytes have?

A

They are ellipsoidal, have dispersed lipid droplets, and numerous mitochondria

130
Q

How do beige adipocytes come to be?

A

Arise from beiging of white adipocyte tissue induced by cold, diet, and exercise

131
Q

Where are pink adipocytes found and why?

A

Animal mammary glands because they are needed for milk fat production

132
Q

What occurs in white adipocytes during the post-prandial phase?

A

Fatty acid uptake, TAG synthesis, and lipid storage

133
Q

What occurs in white adipocyte tissue during the fasting phase?

A

Fatty acid release

134
Q

What is ectopic lipid accumulation?

A

Insufficient lipid retention in white adipose tissue leading to lipid accumulation in other tissues

135
Q

What does leptin do?

A

Suppress appetite, promote energy expenditure, and regulate heat loss

136
Q

What is leptin resistance?

A

The inability to respond to leptin despite sufficient or excess levels in circulation

137
Q

What are lipokines?

A

Lipid hormones which are produced by adipocytes

138
Q

What are microRNAs?

A

Small noncoding RNAs produced by all cells of the body

139
Q

What is proglucagon cleaved to in pancreatic alpha cells?

A

Glucagon-related polypeptide, glucagon, and a C-terminal fragment

140
Q

What is proglucagon cleaved into in neuroendocrine cells?

A

Glicentin, intervening peptide-1, glucagon-like peptide-1, and glucagon-like peptide-2

141
Q

How do GIP, CCK, GLP2, and 5-HT impact glucose absorption in enterocytes?

A

GIP and GLP2 stimulate absorption

CCK and 5-HT decrease absorption

142
Q

How do GIP, GLP2, and 5-HT impact amino acid absorption in enterocytes?

A

GIP and GLP2 increase amino acid absorption

5-HT reduces amino acid absorption

143
Q

How do NTS, SCT, PYY, GLP1, and GLP2 impact lipid absorption in the enterocytes?

A

NTS, SCT, and GLP2 increase lipid absorption

PYY and GLP1 decrease lipid absorption

144
Q

What is the incretin effect?

A

There is higher insulin secretory response with oral glucose administration as compared to intravenous insulin

145
Q

What does DPP4 do?

A

Cleaves proteins which reduces their bioactivity

146
Q

What impacts energy homeostasis?

A

Food intake and energy expenditure

147
Q

What impacts glucose homeostasis?

A

Glucose production and utilization

148
Q

Which neurons sense the body’s energy state?

A

Neuropeptide Y, agouti-related protein, and proopiomelanocortin producing neurons

149
Q

What does the NTS do in response to signals of increased food intake?

A

Activates vagal afferents to reduce food intake

150
Q

What is activated by the preoptic area to promote thermogenesis?

A

The preoptic area dorsomedial hypothalamus rastral raphe pallidus pathway

151
Q

What does the autonomic nervous system do when it is signaled of increased food intake?

A

Modulates pancreatic insulin/glucagon secretion, hepatic glucose production, and skeletal muscle glucose uptake

152
Q

What do central glucoregulatory circuits neurons do?

A

Respond to input from afferent glucose-sensing neurons and project onto and regulate the output from neuroendocrine and autonomic control systems

153
Q

What is type 1 diabetes?

A

An autoimmune disease in which pancreatic islet beta-cells are destroyed

154
Q

What is type 2 diabetes?

A

Insulin resistance and beta-cell dysfunction

155
Q

What is the most effective treatment for people with severe obesity?

A

Bariatric surgery

156
Q

What is dyslipidemia?

A

Disrupted lipid homeostasis leading to high LDL levels

157
Q

What is atherogenic dyslipidemia?

A

Increased fasting triglycerides, low HDL, and small dense LDL

158
Q

What is metabolic syndrome?

A

The co-occurrence of several known cardiovascular risk factors, such as insulin resistance, obesity, atherogenic dyslipidemia, and hypertension

PHPY 303 (3 decks)

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