Physiology Flashcards
1
Q
The large intestine is the principal site of dietary nutrient reabsorption. True/False?
A
False
Small intestine is the principle site of dietary nutrient absorption
2
Q
What are the main functions of the large intestine?
A
Reabsorbs fluid + electrolytes
Stores faecal matter
3
Q
The exocrine and endocrine “parts” of the pancreas are both part of the GI system. True/False?
A
False
Only the exocrine pancreas is part of the GI system
4
Q
Name some accessory structures of the GI tract
A
Salivary glands
Pancreas
Liver
Gall bladder
5
Q
Which muscle - smooth or skeletal - is predominant in the motility of the GI tract?
A
Smooth muscle
6
Q
Which parts of the GI tract are under skeletal muscle control?
A
Mouth + pharynx
Upper oesophagus
External anal sphincter
7
Q
Name two polysaccharides
A
Starch
Glycogen
8
Q
Name two disaccharides
A
Sucrose
Lactose
9
Q
Name three monosaccharides
A
Glucose
Fructose
Galactose
10
Q
What are proteins broken down into?
A
Amino acids
Dipeptides
Tripeptides
11
Q
The apical membrane of an enterocyte faces the lumen. True/False?
A
True
12
Q
Which membrane of an enterocyte faces the blood?
A
Basolateral membrane
13
Q
What are the 4 main layers of the GI tract wall, from innermost to outermost?
A
Mucosa
Submucosa
Muscularis externa
Serosa
14
Q
What is the function of epithelial cells in the mucosa?
A
Absorption
15
Q
What is the importance/function of the muscularis mucosa?
A
Can change shape/SA to facilitate absorption
16
Q
What does contraction of circular muscle do to the lumen of the digestive tract?
A
Makes it narrower and longer
17
Q
What does contraction of longitudinal muscle do to the lumen of the digestive tract?
A
Makes it shorter and fatter
18
Q
What is the function of gap junctions between adjacent smooth muscle cells?
A
Enable slow wave of contraction to spread across smooth muscle sheet
19
Q
Which cells drive slow wave electrical activity?
A
Interstitial cells of Cajal (ICCs)
20
Q
What type of cells are ICCs?
A
Pacemaker cells
21
Q
What must happen for ICCs to produce contraction?
A
Slow wave amplitude must reach threshold to trigger an action potential
22
Q
The upstroke of the AP generated by ICCs is mediated by Na+ influx. True/False?
A
False
Mediated by Ca++ influx through Ca++ channels
23
Q
The force of contraction in the GI tract is related to the number of action potentials discharged from ICCs. True/False?
A
True
The more APs fired, the greater the force of contraction
24
Q
What determines the basal electrical rhythm of the digestive tract?
A
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
