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Aa. Year 1 Questions > Gastrointestinal Physiology > Flashcards

Gastrointestinal Physiology Flashcards

1
Q

What are the pacemaker cells of the GI tract?

A

Interstitial cells of cajal which aloow the basal electrical rhythm

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2
Q

What is the gastroilieal reflex?

A

When food enters the stomach, gastrin is released which feeds-forward and prepares the small intestine for food

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3
Q

What process occurs in the digestive state?

A

Segmentation

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4
Q

What process occurs in the interdigestive (fasting) state?

A

Peristalsis

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5
Q

What is the migrating motor complex?

A

A slowly migrating wave of contraction that occurs across the whole of the small intestine

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6
Q

What inhibits the migrating motor complex?

A

Feeding
Vagal Activity
Gastrin
Cholecystokinin

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7
Q

What triggers the migrating motor complex?

A 
Motilin
Macrolide Antibiotics (mimics motilin)
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8
Q

What is Glucose-Dependent Insulinotropic Peptide?

A

Released from K cells in response to glucose, amino acids and fatty acids
Stimulates insulin release
Inhibits gastric emptying

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9
Q

What is Glucagon-Like Peptide 1?

A

Released from L cells
Stimulates insulin secretion
Inhibits glucagon secretion
Decreases gastric emptying and appetite

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10
Q

What is Motilin?

A

Released from M cells during fasting state

Initiates Migrating Motor Complex

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11
Q

What is Ghrelin?

A

Released from Gr cells

Stimulates appetite

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12
Q

What factors enhances intestinal juice secretion?

A 
Distention
Gastrin
CCK
Secretin
Parasympathetic Nerve Activity
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13
Q

What facetors decreases intestinal juice secretion?

A

Sympathetic Nerve Activity

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14
Q

What is contained within intestinal juice?

A

Mucus - from Goblet Cells

Aqueous Salt - from Bases of the Crypts of Lieberkuhn

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15
Q

Where are the exocrine pancreatic secretions released from?

A

Acinar Cells

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16
Q

Where are the endocrine pancreatic secretions released from?

A

Islet of Langerhans Cells

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17
Q

What are the exocrine pancreatice secretions?

A

Proteases - Trypsinogen, Chymotrypsinogen, Procarboxypeptidase A and B
Amylases - Pancreatic Amylase
Lipases - Pancreatic Lipase

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18
Q

Which group of enzymes are released in an inactive form from the pancreas?

A

Proteases

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19
Q

Which enzyme activates the proteases released from the pnacreas?

A

Enterokinase released from mucosal cells

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20
Q

What are the two types of digestive processes?

A

Luminal digestion

Membrane digestion

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21
Q

What is luminal digestion?

A

This occurs in the lumen. It is mediated by pancreatic enzymes.

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22
Q

What is membrane digestion?

A

This occurs on the external surface of the membrane of microvilli by enteric and absorbed enzymes

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23
Q

What is assimilation?

A

The overall process of digestion and absroption

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24
Q

Name some polysaccharides?

A

Starch

Glycogen

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25
Name some oligosaccharides (3-10 simple sugars)?
Sucrose Lactose Maltose
26
Name some monosaccharides?
Glucose Fructose Galacrose
27
Which enzyme mediates conversion of polysaccharides to oligosaccharides?
Alpha Amylase
28
Which enzyme mediates conversion of oligosaccharides to monosaccharides?
Oligosaccharidases - Lactase Maltase Sucrose-Isomaltase
29
What is the action of alpha amylase?
Breaks down linear internal alpha 1,4 linkages
30
What is the action of lactase?
Brakes down glucose to galactose
31
What is the action of all other oligosaccharidases?
Cleave the terminal alpha 1,4 linkages of maltose, maltotriose and alpha-dextrins
32
Where does the absorption of the final products of carbohydrate digestion occur?
Duodenum and Jejunum
33
How do glucose and galactose cross the apical membrane?
Secondary active transport mediated by SGLT1
34
How does fructose cross the apical membrane?
Facillitated diffusion by GLUT5
35
How do the monosaccharides cross the basolateral membrane?
Facilitated diffusion by GLUT2
36
What is the process of protein digestion in the stomach?
HCl begins to denature proteins | Pepsin cleases the proteins into peptides
37
What is the process of protein digestion in the duodenum?
Pancreatic proteases carry out hydrolysis
38
How do amino acids cross the apical membrane?
There are both Na+ dependent co-transporters and Na+ independent transporters
39
How do amino acids cross the basolateral membrane?
Movement is bidirectional to satisfy enterocytes nutritional requirements. Na+ Independent efflux channels Na+ dependent influx channels
40
How do peptides cross the apical membrane?
PepT1 and SLC15A co-transporters (H+ dependent)
41
How do peptides cross the basolateral membrane?
They are hydrolysed to amino acids within the enterocytes and are then transported across the basolateral membrane as amino acids
42
How are triacylglycerols digested in the stomach?
By gastric lipase which is secreted in response to gastrin
43
How are triacylglycerols digested in the duodenum?
By pancreatic lipase secreted from acinar cells in response to CCK
44
What is the action of pancreatic lipase?
Hydrolyses TAGs at the 1 and 3 positions
45
What is the role of biles salts?
They act as detergents to help emulsify large liquid droplets to small droplets They increase the surface area for attack by pancreatic lipase but block access of the enzyme for TAGs
46
What is colipase?
An amphipathic polypeptide which binds to bile salts and lipase allowing binding between lipase and TAGs
47
How do fatty micelles cross the apical membrane?
By passive diffusion or by membrane fatty-acid translocases, fatty-acid binding protein and fatty-acid transport proteins
48
What happens to long chain fatty acids within the enterocytes?
They are resynthesized to triglycerides in the ER and are incorportared into chylomicrons
49
How is cholesterol absorbed?
Transport by endocytosis in clatherin coated pits by Niemann-Pick C1-Like-1 Protein (NPC1L1)
50
How is Ca2+ absorbed?
Passive - between enterocytes | Active - Ca2+ channes (apical), Ca2+ATpase and Sodium Calcium Exchanger (basolateral)
51
How is Iron reduced?
Only reduced Fe2+ cna be absorbed by the apical membrane therefore reduction is promoted by HCl, Vitamin C, Ferric Reductase, Gastroferrin
52
How is iron absorbed?
Apical - DMT1 Within enterocytes - Transported by mobilferrin Basolateral - Ferroportin 1
53
What controls the ileocaecal valve?
Enteric Neurons Vagus Nerve Sympathetic Nerves Hormonal Signals
54
What is involved in the gastroileal reflex?
Relaxation of the ileocaecal valve/sphincter Increased contractions of the ileum Delivery of chyme from the lieum to the caecum
55
What are the triggers for the gastroileal reflex?
Gastrin | CCK
56
What are the primary functions of the large intestine?
Absorption of Na+, Cl- and H2) Absorption of short chain fatty acids Secretion of K+, HCO3- and mucus Resevoir of colonic ocntents
57
What mediates electroyte abosorption in the large intestine?
Surface epithelial cells
58
What mediates ion secretion in the large intestine?
Crypt cells
59
What secretes mucus in the large intestine?
Goblet cells
60
What is haustration?
Non-propulsive segmentation
61
What are peristaltic propulsive movements?
Mass movement
62
What is defecation?
Periodic egestion
63
What is the gastrocolic reflex?
Presence of food in the stomach is coupled to the mass movement reflex in the colon
64
What stimulates the gastrocolic reflex?
Gastrin | Enteric nerve plexuses
65
What provides the osmotic force for the absorption of water?
Na+
66
What are the 5 principle mechanisms of Na+ absorption?
``` Na+/glucose co-transport Na+/amino acid co-transport Na+/H+ exchange Parallel Na+/H+ and Cl-/HCO3- exchange Epithelial Na+ Channels ```
67
What factors reduce Parallel Na+/H+ and Cl-/HCO3- exchange?
Intracellular cAMP, cGMP and Ca2+
68
What regulates epithelial Na+ channels?
Aldosterone
69
Where is Cl- secreted from?
Crypt cells
70
What activates the CFTR protein?
Bacterial enterotoxins Hormones and neuortransmitters Immune cell products Some laxatives
71
What is the overall effect of the opening of CFTR proteins?
Secretory diarrhoea
72
What are the main neurotransmitter systems involved in nausea and vomiting?
5-HT Dopamine ACh
73
What area of the brain can cause nausea and vomiting?
Chemoreceptor trigger zone
74
What is the action of Vasoactive Intestinal Peptide?
Stimulates secretion by the pancreas and intestines | Inhibits acid secretion
75
Where is somatostatin released from?
D cells
76
Where is CCK released from?
I cells
77
Where are bile salts absorbed?
Terminal Ileum

Aa. Year 1 Questions (12 decks)

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