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Flashcards in Physiology Deck (200)
1

The large intestine is the principal site of dietary nutrient reabsorption. True/False?

False
Small intestine is the principle site of dietary nutrient absorption

2

What are the main functions of the large intestine?

Reabsorbs fluid + electrolytes
Stores faecal matter

3

The exocrine and endocrine "parts" of the pancreas are both part of the GI system. True/False?

False
Only the exocrine pancreas is part of the GI system

4

Name some accessory structures of the GI tract

Salivary glands
Pancreas
Liver
Gall bladder

5

Which muscle - smooth or skeletal - is predominant in the motility of the GI tract?

Smooth muscle

6

Which parts of the GI tract are under skeletal muscle control?

Mouth + pharynx
Upper oesophagus
External anal sphincter

7

Name two polysaccharides

Starch
Glycogen

8

Name two disaccharides

Sucrose
Lactose

9

Name three monosaccharides

Glucose
Fructose
Galactose

10

What are proteins broken down into?

Amino acids
Dipeptides
Tripeptides

11

The apical membrane of an enterocyte faces the lumen. True/False?

True

12

Which membrane of an enterocyte faces the blood?

Basolateral membrane

13

What are the 4 main layers of the GI tract wall, from innermost to outermost?

Mucosa
Submucosa
Muscularis externa
Serosa

14

What is the function of epithelial cells in the mucosa?

Absorption

15

What is the importance/function of the muscularis mucosa?

Can change shape/SA to facilitate absorption

16

What does contraction of circular muscle do to the lumen of the digestive tract?

Makes it narrower and longer

17

What does contraction of longitudinal muscle do to the lumen of the digestive tract?

Makes it shorter and fatter

18

What is the function of gap junctions between adjacent smooth muscle cells?

Enable slow wave of contraction to spread across smooth muscle sheet

19

Which cells drive slow wave electrical activity?

Interstitial cells of Cajal (ICCs)

20

What type of cells are ICCs?

Pacemaker cells

21

What must happen for ICCs to produce contraction?

Slow wave amplitude must reach threshold to trigger an action potential

22

The upstroke of the AP generated by ICCs is mediated by Na+ influx. True/False?

False
Mediated by Ca++ influx through Ca++ channels

23

The force of contraction in the GI tract is related to the number of action potentials discharged from ICCs. True/False?

True
The more APs fired, the greater the force of contraction

24

What determines the basal electrical rhythm of the digestive tract?

Slow wave electrical activity

25

All slow waves trigger contraction. True/False?

False
Threshold must be reached first

26

What is the net direction of luminal contents in the small intestine? Why?

Aboral direction
Fduodenum greater than Fileum

27

What is the net direction of luminal contents in the large intestine? Why?

Oral direction
Fdistalcolon greater than Fproximalcolon in order to allow some reabsorption to take place

28

What connects myenteric and submucosal plexi?

Interganglionic fibre tracts

29

What is the nervous system of the gut called?

Enteric nervous system

30

The parasympathetic system plays a bigger role in the enteric nervous system than the sympathetic system. True/False?

True

31

Parasympathetic outflow is thoraco-lumbar. True/False?

False
Cranio-sacral

32

Which nerve provides parasympathetic cranial outflow?

Vagus nerve

33

Which nerve provides parasympathetic sacral outflow?

Pelvic nerves

34

Post-ganglionic neurones are essentially intrinsic to the ENS. True/False?

True

35

Name a local nerve reflex of the GI tract

Peristalsis

36

Name a short nerve reflex of the GI tract

Intestino-intestinal reflex

37

What is the intestino-intestinal reflex?

Overdistention in one area of the intestine causes relaxation in the rest of the intestine

38

Name a long nerve reflex of the GI tract

Gastroileal reflex

39

What is the gastroileal reflex?

Stomach signals increase motility of the ileum - open the ileocaecal valve to empty chyme to prepare ileum to receive fresh chyme from the stomach

40

What happens to the propulsive (oral) segment in peristalsis?

Circular muscle contracts
Longitudinal muscle relaxes

41

What happens to the receiving (aboral) segment in peristalsis?

Circular muscle relaxes
Longitudinal muscle contracts

42

Which substances mediate contraction of circular/longitudinal muscle?

ACh
Substance P

43

Which substances mediate relaxation of circular/longitudinal muscle?

VIP
NO

44

What is the process of segmentation called in the large intestine?

Haustration

45

The upper oesophageal sphincter is controlled by smooth muscle. True/False?

False
Skeletal muscle

46

The lower oesophageal sphincter is controlled by smooth muscle. True/False?

True

47

Which anal sphincter - internal or external - is controlled by skeletal muscle?

External anal sphincter

48

Which receptors are stimulated when food reaches the pharynx? What do they do?

Pharyngeal pressure receptors send afferent impulses to the swallowing centre in the medulla

49

In swallowing, what happens to the larynx? Why?

Elevates to prevent food from entering the trachea

50

In peristalsis, circular fibres in front of the bolus contract. True/False?

False
Circular muscle behind the bolus contracts

51

What happens if food becomes lodged in the oesophagus?

Secondary peristaltic wave, more forceful than the first, is triggered locally

52

What are the 3 major pairs of salivary glands and their locations?

Parotids - over the masseter below ears
Submandibular - lower edge of mandible
Sublingual - under tongue

53

Sublingual salivary gland contribute towards 70% of saliva. True/False?

False
Submandibular gland contributes 70% of saliva

54

How much saliva is contributed to by the parotid glands?

25%

55

What are the antibacterial components of saliva?

Lysozyme
Lactoferrin
Immunoglobulins

56

What is xerostomia?

Dry mouth syndrome due to inadequate production of saliva

57

Primary saliva secretion occurs from where?

Acinus

58

Secondary saliva secretion occurs from where?

Duct cells

59

What does the primary saliva secretion consist of?

Na, K, Cl and HCO3

60

How is the primary saliva secretion modified by duct cells?

Remove Na and Cl
Add some K and HCO3
Diluted as no H2O movement

61

NaCl content of saliva is lower than that of the plasma. True/False?

True

62

Glucose content of saliva is higher than that of the plasma. True/False?

False
No glucose in saliva

63

When flow rate is high, HCO3 content of the saliva increases. True/False?

True

64

How does the simple (unconditioned) reflex stimulate salivary glands to increase saliva production?

Pressure receptors in mouth activate in presence of food and sent afferent impulses to salivary centre in the medulla

65

How does the conditioned reflex stimulate salivary glands to increase saliva production?

Think/smell/see food activates cerebral cortex which activates salivary centre in the medulla

66

Which nerves carry parasympathetic innervation of saliva production control?

Facial nerve
Glossopharyngeal nerve

67

What is the effect of parasympathetic stimulation upon saliva production?

Large volume
Watery
Enzyme rich

68

What is the effect of sympathetic stimulation upon saliva production?

Low volume
Thick
Mucus rich

69

What are the 4 main anatomical areas of the stomach?

Fundus
Body
Antrum
Pylorus

70

Where does most mixing/churning of food take place in the stomach?

Antrum

71

What is the substance produced when food mixes with gastric secretions?

Chyme

72

Name a substance which can be absorbed by the stomach

Ethanol

73

Thickness of smooth muscle lining decreases distally in the stomach. True/False?

False
Increasing thickness distally (antrum thickness greater than fundus thickness)

74

What occurs in Retropulsion?

Peristaltic wave forces chyme against closed pyloric sphincter, so chyme bounces back and undergoes more mixing

75

Name 2 gastric factors promoting gastric emptying

Volume of chyme (larger volume increases motility due to distention)
Consistency of chyme (thinner liquid facilitates emptying)

76

Which 2 duodenal factors delay gastric emptying?

Enterogastric reflex
Release of enterogastrones

77

What is the enterogastric reflex?

Duodenum signals to stomach that it has enough chyme so slow down emptying/peristaltic contraction

78

What is the effect of enterogastrones on gastric emptying?

CCK and secretin release from duodenum inhibit stomach contraction

79

Where is the pyloric gland area located?

Antrum

80

Where is the oxyntic mucosa area located?

Fundus and Body

81

Which cells are contained in the pyloric gland area?

D cells
G cells

82

What do D cells secrete?

Somatostatin

83

What do G cells secrete?

Gastrin

84

Which cells are contained in the oxyntic mucosa?

Parietal cells
Enterochromaffin-like cells
Chief cells

85

What do ECL cells secrete?

Histamine

86

What do parietal cells secrete?

HCl
Intrinsic factor

87

What do chief cells secrete?

Pepsinogen

88

What does autocatalytic mean with regards to pepsinogen and pepsin?

Pepsin formation triggers further pepsin formation from pepsinogen

89

What is the role of intrinsic factor in the oxyntic mucosa?

Binds vitamin B12

90

What is the role of histamine in the oxyntic mucosa?

Stimulates HCl secretion

91

What is the role of gastrin in the pyloric gland area?

Stimulates HCl secretion

92

What is the role of somatostatin in the pyloric gland area?

Inhibits HCl secretion

93

In the gastric parietal cell, present in the gastric pit of the ____ ____, CO2 and H2O combine under the enzyme ____ ____ which dissociates to form _ and ___.
___ is transported out of the cell via an antiporter in exchange for __, which is driven out into the canaliculus.
_ is secreted into the canaliculus via the ___ ___, and combines with __ to form ___.

In the gastric parietal cell, present in the gastric pit of the oxyntic mucosa, CO2 and H2O combine under the enzyme carbonic anhydrase which dissociates to form H+ and HCO3.
HCO3 is transported out of the cell via an antiporter in exchange for Cl, which is driven out into the canaliculus.
H+ is secreted into the canaliculus via the proton pump, and combines with Cl to form HCl.

94

What are Secretagogues?

Substances promoting secretion of HCl (gastrin, ACh, histamine)

95

In response to Secretagogues, where do proton pumps move from and to in the parietal cell?

Move from inactive tubulovesicles in the cytoplasm to being active in the apical membrane

96

What are the 3 phases of gastric secretion?

Cephalic
Gastric
Intestinal

97

What is involved in the cephalic phase?

Stomach is prepared to receive food by conditioned reflex, chewing or swallowing, leading to gastric secretion through ACh and GRP

98

What is involved in the gastric phase?

Distention due to food causes mechanoreceptors to augment secretion

99

What is involved in the intestinal phase?

Gastric secretion is halted through secretin, CCK and somatostatin as the stomach empties

100

What is the importance of the mucus gel layer on the surface of mucous secreting cells?

Prevents pepsin/HCl reaching the apical surface of the cells and damaging the cells

101

What are the two forms of starch?

Amylose
Amylopectin

102

Amylose and amylopectin are branched chain molecules. True/False?

False
Amylose isn't but amylopectin is branched

103

Which type of bond links glucose monomers in amylose?

alpha-1,4

104

Which type of bonds link glucose monomers in amylopectin?

alpha-1,4
alpha-1,6 for branched chain

105

Glycogen is a branched chain polysaccharide. True/False?

True

106

Which type of bond links glucose monomers in glycogen?

alpha-1,4
alpha-1,6

107

Name two oligosaccharides (disaccharides)

Lactose
Sucrose

108

Which monomers make up sucrose?

Glucose and fructose

109

Which monomers make up lactose?

Glucose and galactose

110

Which enzyme carries out luminal digestion of starch?

alpha-amylase

111

What is starch broken down into in luminal digestion?

Oligosaccharides - e.g. maltose

112

Which enzymes carry out brush border digestion of maltose, lactose and sucrose?

Maltase
Lactase
Sucrase-isomaltase

113

What are oligosaccharides such as lactose, maltose and sucrose broken down into in brush border digestion?

Monosaccharides - e.g. glucose, fructose, galactose

114

Alpha-amylase breaks down all alpha-1,4 glucose linkages. True/False?

False
Only breaks down linear internal links - not terminal links, hence no production of glucose

115

Lactase can only break down lactose. True/False?

True

116

How is isomaltase unique?

It is the only enzyme that can split the branching of alpha-1,6 linkages

117

What is lactose intolerance?

Inability to digest lactose, caused by lactase insufficiency

118

Absorption of monosaccharides involves entry via the basolateral membrane and exit via the apical membrane. True/False?

False
Other way around!

119

What is meant by secondary active transport?

Transport either via cotransport or antiport

120

What are oligopeptides?

Dipeptides
Tripeptides
Some tetrapeptides
[products of protein digestion]

121

What denatures proteins in the stomach?

HCl

122

Which enzyme cleaves protein into peptides in the stomach?

Pepsin

123

Is pepsin essential for protein digestion?

No

124

What are the active enzymes that digest protein in the duodenum?

Trypsin
Chymotrypsin
Elastase
Procaroxypeptidase A
Procaroxypeptidase B

125

Where does most fat digestion take place?

Small intestine

126

Which enzyme cleaves off fatty acids from triglycerides in the stomach?

Gastric lipase

127

What is the main lipid digesting enzyme in the duodenum?

Pancreatic lipase

128

What do bile salts do to large lipid droplets?

Emulsify them into smaller droplets with a larger SA to increase affinity for lipase

129

Which enzyme acts as a cofactor for lipase to help it gain access to the triglyceride chain?

Colipase

130

Digestion of triglyceride by pancreatic lipase produces glycerol + 3 fatty acids. True/False?

False
Produces monoglyceride + 2 fatty acids

131

What is a mixed micelle?

Emulsified fat globule containing monoglyceride, fatty acids, phospholipid, bile salt and cholesterol

132

How are short and medium -chain fatty acids absorbed into capillaries?

Exit basolateral membrane via diffusion

133

What happens to long-chain fatty acids and monoglycerides once in the enterocyte?

Resynthesised to triglyceride in the ER and incorporated into chylomicrons

134

What coats the cholesterol ester-triglyceride complex to form a chylomicron?

Apolipoprotein (apo-B48)

135

How does the chylomicron exit the enterocyte? Where does it go?

Exocytosis into the lymphatic system

136

Which enzyme metabolises chylomicrons?

Lipoprotein lipase

137

What carries the free fatty acids and glycerol released by chylomicron degradation?

Albumin

138

What does a chylomicron remnant consist of?

Cholesterol and phospholipid

139

Which protein allows cholesterol absorption?

NPC1L1 protein

140

How does the scaffold containing cholesterol bound to NPC1L1 move around the cell?

Via myosin runners

141

When calcium concn is low, it is absorbed via Ca channels. Which vitamin increases expression for these channels?

Vitamin D

142

Ferric iron can be absorbed by the enterocyte. True/False?

False
Must be converted to ferrous iron (Fe2)

143

Ferrous iron can be absorbed via a cotransporter. Which ion is coupled with its transport?

H+
i.e. H+ dependent cotransport of iron

144

What is the other mechanism (other than receptor transport) by which iron can be absorbed by the enterocyte?

Through haem - haem is taken up and degraded by haem oxidase

145

What is the storage form of iron called?

Ferratin

146

What are the ranges for normal BMI?

18.5-25

147

What are the ranges for BMI classed as overweight?

25-29

148

What are the ranges for BMI classed as obese?

30-39

149

What are the ranges for BMI classed as morbidly obese?

Greater than 40

150

How is obesity "a disease of the brain"?

The brain sees new fat/weight as normal, and attempts to lose weight are seen as a threat to survival, so the new weight is defended

151

Lesioning ventromedial hypothalamus causes leanness. True/False?

False
Lesioning ventromedial hypothalamus causes obesity

152

Which lesioning part of the hypothalamus causes leanness?

Lateral part

153

Define satiation

Feeling of fullness during/following a meal

154

Define satiety

Period from end of one meal to beginning of next

155

What effects do satiation signals have during a meal?

Increased signals limit meal size, i.e. you can't eat anymore

156

What is ghrelin?

A hunger signal - levels increase before a meal and decrease after a meal

157

Which 2 hormones report the "fat status" of fat stores to the brain?

Leptin
Insulin

158

Levels of leptin and insulin increase in the blood as more fat is stored. True/False?

True

159

Reduced leptin mimics starvation. True/False?

True

160

Name a drug that can be prescribed to tackle obesity

Orlistat

161

How does Orlistat work?

Inhibits pancreatic lipase to decrease triglyceride absorption

162

Vomiting is due to stomach contraction. True/False?

False
Stomach, oesophagus + sphincters are relaxed

163

Which centre coordinates vomiting in the brainstem?

Vomiting centre (VC) in the medulla oblongata

164

Does nausea always cause vomiting?

No

165

Toxic materials stimulate enterochromaffin cells to release which mediator of vomiting?

5-HT (serotonin)

166

Which 3 stimulants stimulate the CTZ in the brainstem to act on the VC to initiate vomiting?

Toxins
Mechanical activity/disease
Motion sickness

167

What effects do vagal efferents have on the oesophagus, stomach and small intestine in the vomiting reflex?

Oesophagus shortens
Stomach relaxes
Small intestine retrograde contraction

168

Place the parts of the small intestine in order from shortest to longest

Duodenum (0.25m)
Jejunum (2.5m)
Ileum (3m)

169

Which 3 components increase the SA of the small intestine?

Circular folds
Villi
Microvilli

170

Where is gastrin secreted from?

G cells of stomach + duodenum

171

Where is CCK secreted from?

I cells of duodenum + jejunum

172

Where is secretin secreted from?

S cells of duodenum

173

Where is motilin secreted from?

M cells of duodenum + jejunum

174

Where is ghrelin secreted from?

Gr cells of stomach, small intestine + pancreas

175

Distention, gastrin, CCK, secretin + parasympathetic activity all enhance the secretion of intestinal juice. True/False?

True

176

What is the migrating motor complex in the small intestine?

Strong peristaltic contraction spanning from stomach to end of ileum which clears debris and mucus between meals (housekeeper - migrating "mother" complex!)

177

Gastrin and CCK trigger the migrating motor complex. True/False?

False
Motilin triggers it; CCK and gastrin inhibit it

178

The exocrine pancreas secretes digestive enzymes from ____ cells and aqueous salt from ____ cells, collectively called pancreatic juice

The exocrine pancreas secretes digestive enzymes from acinar cells and aqueous salt from duct cells

179

What does the aqueous salt solution released from pancreatic duct cells do?

Neutralises acidic chyme in the duodenum

180

In the duodenum, proton is lost/added to blood and bicarbonate is lost/added to lumen; in the stomach, proton is lost/added to lumen and bicarbonate lost/added to blood

In the duodenum, proton is lost to blood and bicarbonate is added to lumen; in the stomach, proton is added to lumen and bicarbonate lost to blood

181

Acid/chyme in duodenum stimulates/inhibits the release of secretin, which stimulates/inhibits release of intestinal juice from pancreas

Acid/chyme in duodenum stimulates the release of secretin, which stimulates release of intestinal juice from pancreas

182

Fat and protein in the duodenum stimulates/inhibits the release of CCK, which stimulates/inhibits release of intestinal juice from pancreas

Fat and protein in the duodenum stimulates the release of CCK, which stimulates release of intestinal juice from pancreas

183

Describe haustration

Intermittent contraction of circular muscle in proximal colon at slow rate to allow contents to move but leave enough opportunity for reabsorption

184

Which nerve conveys efferents to cause either relaxation or contraction of the external anal sphincter?

Pudendal nerve

185

Reabsorption of water is largely driven by the reabsorption of which salt?

Sodium

186

Which mechanism is the most major in Na reabsorption in the post-prandial period in the jejunum?

Na-glucose and Na-amino acid cotransport

187

What is the effect of cAMP, cGMP and Ca2+ on NaCl absorption?

Reduce NaCl absorption

188

Where do epithelial Na channels (ENaC) mediate Na absorption?

Distal colon

189

Where does blood from the hepatic artery and hepatic portal vein meet and mix in the liver?

Sinusoids (fenestrated capillaries that enable blood to leak out into space of Disse)

190

The liver is made up of hexagonal lobules. List the vessels and ducts contained in each lobule

Central vein (branch of hepatic vein)
Portal triad (hepatic portal branch + hepatic artery branch + bile duct)

191

What is the direction of blood flow in a liver lobule?

Inwardly through sinusoids towards the central vein

192

What is the direction of bile flow in a liver lobule?

Outwardly through canaliculi towards the bile duct

193

Canaliculi are formed by the basolateral membrane. True/False?

False
Canaliculi are formed by the apical membrane

194

Which membrane faces the space of Disse?

Basolateral membrane

195

Which 3 types of cell are located in the sinusoidal spaces?

Endothelial cells
Kuppfer cells
Stellate (Ito) cells

196

What is the function of endothelial cells in the sinusoidal space?

Fenestrated structure allows passage of solute, but not cells

197

What is the function of Kuppfer cells in the sinusoidal space?

Macrophages that remove bacterial matter and dead RBCs

198

What is the function of Stellate (Ito) cells in the sinusoidal space?

Store vitamin A within the space of Disse
May deposit collagen, beginning liver cirrhosis

199

Most bile is secreted by bile duct cells. True/False?

False
Most is secreted by the liver

200

Most of the bile entering the duodenum is reabsorbed in the terminal ileum. True/False?

True