GIT Physiology Flashcards
1
Q
What type of amylase is the salivary one?
A
alpha-amylase
1
Q
Where does pepsin act on its target molecule?
A
It hydrolyses the bound between a aromatic aa and a second aa
1
Q
What is emulsifying?
A
Breaking up fats into droplets
2
Q
What is vitamin C also known as?
A
L-Ascorbic acid
3
Q
What is the function of Gastrin releasing peptide?
A
Acts in parallel with ACh from vagus to stimulate gastrin release from G cells
4
Q
What is the effect of the release of secretin stimulated bicarbonate solution from the pancreas?
A
Neutralised acid and pepsin activity
This leads to reduced stimulation of stomatostatin release from duodenal D cells and stops the vago-vagal and duodenal-pyloric-antral reflexes inhibiting gastric emptying
4
Q
What type of cells can sense sweet taste?
A
L cells
4
Q
What type of cells express olfactory receptors?
A
EC cells
4
Q
Why don’t most things taste good without fats?
A
Most odourants/favour molecules are fat soluble
4
Q
If tri or dipeptides are absorbed in to the enterocytes what must happen to them?
A
Cleaves into single aa’s by small peptidases
4
Q
How many transport systems are there for free aa’s?
A
7
5
Q
What is the function of mucus and bicarbonate release in the duodenum?
A
Create a barrier to gastric acid
5
Q
What is the result of L cells sensing sweetness?
A
Increased glucose absorption
5
Q
To what level are proteins digested before they can be absorbed?
A
Tri-, Di-peptides and single aa’s
6
Q
What does colon fermentation produce?
A
Short chain fatty acids
7
Q
How is cholesterol esterase activated?
A
By bile
8
Q
What is the function of Ghrelin?
A
It is released from the stomach in fasted state to increase appetite
9
Q
Which enzyme is important for breaking cell-cell adhesion?
A
Pepsin
10
Q
5 of the amino acid absorption systems require what for co-transport?
A
Na - similar to sodium-dependent glucose transporters (SGLT1)
11
Q
If you don’t have a stomach what supplement do you require?
A
Intrinsic factor
12
Q
Which cell secrete pepsinogen?
A
Chief cells
13
Q
Do gastric lipases play a major role in lipid digestion?
A
No
14
Q
What does the vagovagal reflex pathway control/regulate?
A
Swallowing
Acid secretion
Smooth muscle contraction in stomach and duodenum
15
Q
What is the product of fibre fermentation?
A
Short chain fatty acids
16
What neural pathway activates the cephalic phase?
The vagus nerve
17
What are the basic functions of the GIT?
Digest food
Absorb nutrients
Excrete waste
Prevention of invasion by pathogens
Contain the microbiome
17
Where are the major sites of digestion?
Duodenum and upper jejunum
19
What is the last to empty from the stomach? What are the implications?
Fat
Massive increase in CCK release when it come through
20
Which enzyme digests sucrose? What are the products of its digestion?
Sucrase
Glucose and fructose
20
Which enzyme activates enzymes from the pancreatic juices?
Enterokinase
21
What is the name of the enzyme that digests sugars?
Amylase
22
What does the endocrine control system regulate?
Secretion of enzymes and solvents into the intestinal lumen
Helps regulate appetite
23
What are two disaccharides human digested commonly?
Lactose and sucrose
23
What enzymes cleave at the amino end of peptide chains?
Aminopeptidases
24
What is the major transporter for glucose absorption?
Sodium-dependent glucose transporter - Na provides the energy
25
Which hormone's release is stimulated by tastants?
Serotonin (EC cells)
25
Where is conscious control required in the defecation process?
Relaxation of anal sphincter
Contraction of abdominal muscles
25
Does the salivary amylase make it through the stomach?
Yes and it is reactivated once the pH returns to neutral
25
What are micelles composed of?
Bile salts with lecithin and monoglycerides
26
How are fats absorbed into the epithelium?
Micelles come into contact with lipid membrane and lipids dissolve and enter cells
28
What do enterochromaffin cell-like cell release?
Histamine
30
What three factors stimulate gastric acid secretion in parietal cells?
Vagus stimulation via enteric nerves releasing ACh acting on parietal cells
Histamine for enterochromaffin cell-like cell
Gastrin from G cells in the antrum (of stomach) and duodenum (endocrine signalling - must travel through the portal system)
31
What does cholesterol esterase do?
Hydrolyse cholesterol esters and esters of fat soluble vitamins and phospholipids
32
What happens to fat in the stomach?
It floats to the top due to action of acid, pepsin and mechanical action
33
What happens if the lower oesophageal sphincter doesn't close properly?
Oesophageal reflux
If chronic - can lead to GORD - gastrooesophageal reflux disease
34
What happens to fatty acids and monoglycerides inside epithelials cells?
They form triglycerides in the smooth endoplasmic reticulum
35
How does somatostatin act on parietal cells?
By paracrine action directly on parietal cells to dampen acid secretion and,
By inhibiting histamine (which stimulates parietal cell acid secretion) release in enterochromaffin cell-like cells
37
What mechanism of sensing are present in the intestine lumen?
Mechanical reception - distension and mucosal deformation
Chemical stimuli
37
What type of vessel do chylomicrons get exocytosed into for enterocytes?
Lymphatics
39
What happens when the GIT is activated during the cephalic stage of eating?
Salivation begins
Gastric acid pepsin secretion begins
The gastric body and fundus relax
41
What four functions must be regulated in the GIT?
Contractions of muscles to mix food
Secretion of digestive enzymes
Re-absorption of water
Coordination of separate regions
43
When food initially enters the duodenum, what is the fat content?
Low
44
What linkage can't pancreatic and salivary amylase digest?
1:6alpha
45
What does the CNS control in relation to food?
Anticipation
Mood/activity - fight or flight responses
46
Does glucose and fructose require digestion in the GIT?
No, they are immediately absorbed
47
Triglycerides are covered by what to form chylomicrons?
Apolipoproteins
48
Where do aa go after being absorbed into enterocytes?
Blood \> portal circulation \> liver
49
Which enzyme acts at the carboxy end of polypeptides?
Pancreatic carboxypeptidases
50
Which transporter facilitates fructose transport into the epithelium?
GLUT5
52
What is the consistency of the food when it leaves the antrum?
Diluted paste
53
What enzymes digest maltotriose and maltose?
Isomaltase
Sucrose
Maltase
54
Which endocrine signal induces expression of alpha-amylase in the pancreas?
CCK
56
What is segmentation?
A motor pattern in the duodenum where there are alternate contrictions and relaxations to further mix food with digestive enzymes and bile and bring it into contact with the epithelium for absorption
57
Via what pathway does acid trigger the release of mucus and bicarbonate by Brunner's cells?
Vagal afferent neurones trigger the vago-vagal reflex
58
What stimulates the urge to defecate?
Distension of the rectum
59
What is sacrose a polymer of?
Glucose and fructose
60
Distension of the stomach causes what?
Activation of enteric and vago-vagal reflexes that lead to more acid and pepsin release
61
What is fermented in the distal small intestine and colon?
Cellulose
62
How is it insured that pancreatic enzymes are only active once they reach the food?
With a multi-dependent activation cascade.
63
Why must pepsin have an inactivated form?
So it doesn't digest the contents of the cells it's stored in
64
Which sugar polymers are digested at the brush boarder?
Oligosaccharides
Disaccharides
65
Why must D cells in the duodenum release much greater amounts of somatostatin cf to those in the stomach for it to have it desired effect?
It must travel through the portal system and the whole body therefore it is diluted
67
At what point does the microbiota metabolism start?
Ileum and colon
67
What linkage does alpha-amylase hydrolyse?
1:4alpha
68
How does activation of sweet taste receptors increase glucose absorption?
It activates glucose-Na channels
70
Where is primary peristalsis generated from? How is it communicated to the GIT?
The brain
Vagus nerve
71
Why might initial acid digestion in the mouth be important?
Initiates preparation of lipid storage
73
Which enzyme can break I:6alpha linkages?
Isomaltase
74
What are the name of the intrinsic pacemaker cells in the muscles?
Interstitial cells of Cajal
74
Does fat digestion occur in the mouth?
Yes, starts with lingual lipase
75
What is the first thing that must happen when food enters the duodenum?
Neutralise acids
77
What does cholecystokinin excite? What is the effects? (there are three)
Afferent vagal nerves that act on the hypothalamus to suppress appetite
Enteric sensory neurones to activate motor action to mix food
Contraction of gall bladder for secretion and pancreatic digestive enzymes secretion
79
What is the function of the neurally regulated interdigestive motor complex?
Clear bacteria to prevent overgrowth
80
Amino acids and fatty acids stimulate release of what from which cells?
CCK (cholecystokinin) from I cells
Secretin from S cells (just AA's)
81
T/F the majority of movement in the intestines after a meal is propulsion?
False, 90% is mixing
82
What is retropulsion?
Food pushed back towards pyloris to facilitate mixing with pancreatic duct secretions and bile - further digestion
83
Which transporter facilitate fructose transport from the epithelium to the interstitium?
GLUT2
84
What is the function of secretin?
Stimulate secretion of a bicarbonate solution from the pancreas
85
How is lipase activated?
Colipase activates it
Colipase is activated by trypsin
87
What does the enteric nervous system and institial cells of Cajal regulate?
Contractile activity and secretion of water and salt
88
Why do enteroendocrine cells often span the epithelium?
So they can release mediators into the lumen of the GIT or into the blood stream
89
Which endocrine hormone is required for secretion of pancreatic lipolytic enzymes?
CCK
91
What are the 4 responses to acid in the duodenum?
Activates D cells to release somatostatin
Activates to Brunner's glands produce mucus and bicarbonate
Activates the vago-vagal reflex to stop gastric emptying
Duodenal-pyloro-antral reflex closes the pylorus to further prevent gastric emptying
92
Which is absorbed better, glucose or fructose?
Glucose
93
Are enzymes released in the pancreas active?
No, they're in their inactivated form
94
Where do trypsin, elastase and chymotrypsins act on their substrates (it's the same for each of them)?
At the interior bonds of peptides to produce short polypeptides
95
Where is pepsinogen I secreted?
Acid secreting region of the stomach
97
T/F Smooth muscle cells of the GIT have intrinsic pacemakers
True
99
How do active maltase and sucrase get to their site of action?
An inactivated pro form is placed on the mucosal membrane as combined glycoprotein until pancreatic proteases cleave them to activate them
100
What does digestion by pancreatic carboxypeptidases produce?
single aa's
101
Where is pepsinogen II secreted?
Pylorus
102
What does the body and antrum of the stomach do before food enters?
Reflex to accommodate
103
T/F Cellulose and starch are resistant to digestion.
False, only cellulose
104
What emulsifies lipids in the GIT?
Bile salt and lecithin
105
What is the cephalic stage of eating?
The sight and smell of food initates aspects of the GIT including salivation. The site of food will affect how it tastes eg red lollies taste "sweeter"
106
What does pepsinogen become?
Pepsin
107
What activates pepsinogen secretion by chief cells?
Gastrin
108
What controls swallowing?
Somatic NS via vagus
109
Where is CCK released in sugar digestion?
Duodenal mucosa
110
What stimulates D cells to release somatostatin?
Vagal stimulation via the enteric ns releasing ACh
Gastrin released from G cells
Acid in the stomach
111
What is the response to food entering the fundus?
Inhibition of acid secretion in the body
112
How are short chain fatty acids absorbed?
In a H+ dependent manner in the distal small intestine and colon
113
What factor tones down gastric acid secretion by parietal cells? Which cells release it?
Somatostatin
D cells
114
What are enteroendocrine cells?
GIT signally cells that contain many different hormone signalling molecules
