Physiology Flashcards
1
Q
The large intestine is the principal site of dietary nutrient absorption.
True/ False?
A
False
The small intestine is the principle site of dietary nutrient absorption.
2
Q
Which muscle type is predominant in the motility of the GI tract?
A
Smooth muscle
3
Q
What are the main functions of the large intestine?
A
Reabsorbs fluid + electrolytes
Stores faecal matter
4
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.
5
Q
Name some accessory structures of the GI tract!
A
Salivary glands
Pancreas
Liver
Gall bladder
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 the lumen shape/ surface area 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 nervous system of the gut called?
Enteric nervous system
27
The parasympathetic system plays a bigger role in the enteric nervous system than the sympathetic system.
True/ False?
True
28
The submucous plexus mostly regulates ---.
| The myenteric plexus mostly regulates ---.
The submucous plexus mostly regulates epithelia and blood vessels.
The myenteric plexus mostly regulates motility and sphincters.
29
Parasympathetic outflow is thoraco-lumbar.
| True/ False?
False
| Cranio-sacral
30
Which nerve provides parasympathetic cranial outflow?
Vagus nerve
31
Which nerve provides parasympathetic sacral outflow?
Pelvic nerves
32
Post-ganglionic neurones are essentially intrinsic to the ENS.
True/ False?
True
33
Name a local nerve reflex of the GI tract!
Peristalsis
34
Name a short nerve reflex of the GI tract!
Intestino-intestinal reflex
35
What is the intestino-intestinal reflex?
Overdistention in one area of the intestine causes relaxation in the rest of the intestine
36
Name a long nerve reflex of the GI tract!
Gastroileal reflex
37
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
38
What happens to the propulsive (oral) segment in peristalsis?
Circular muscle contracts
| Longitudinal muscle relaxes
39
What happens to the receiving (aboral) segment in peristalsis?
Circular muscle relaxes
| Longitudinal muscle contracts
40
Which substances mediate contraction of circular/ longitudinal muscle?
ACh
| Substance P
41
Which substances mediate relaxation of circular/longitudinal muscle?
VIP
| NO
42
What is the process of segmentation called in the large intestine?
Haustration
43
The upper oesophageal sphincter is controlled by smooth muscle.
True/ False?
False
| Skeletal muscle
44
The lower oesophageal sphincter is controlled by smooth muscle.
True/ False?
True
45
Which anal sphincter is controlled by skeletal muscle?
External anal sphincter
46
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
47
What happens to the larynx during swallowing?
Elevates to prevent food from entering the trachea
48
What happens if food becomes lodged in the oesophagus?
Secondary peristaltic wave, more forceful than the first, is triggered locally
49
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
50
Sublingual salivary gland contribute towards 70% of saliva.
| True/ False?
False
| Submandibular gland contributes 70% of saliva
51
How much saliva is contributed to by the parotid glands?
25%
52
What are the antibacterial components of saliva?
Lysozyme
Lactoferrin
Immunoglobulins
53
What is xerostomia?
Dry mouth syndrome due to inadequate production of saliva
54
Primary saliva secretion occurs from where?
Acinus
55
Secondary saliva secretion occurs from where?
Duct cells
56
What does the primary saliva secretion consist of?
Na, K, Cl and HCO3
57
How is the primary saliva secretion modified by duct cells?
Remove Na and Cl
Add some K and HCO3
Diluted as no H2O movement
58
NaCl content of saliva is lower than that of the plasma.
| True/ False?
True
59
Glucose content of saliva is higher than that of the plasma.
True/ False?
False
| No glucose in saliva
60
When flow rate is high, HCO3 content of the saliva increases.
True/ False?
True
61
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
62
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
63
Which nerves carry parasympathetic innervation of saliva production control?
Facial nerve
| Glossopharyngeal nerve
64
What is the effect of parasympathetic stimulation upon saliva production?
Large volume
Watery
Enzyme rich
65
What is the effect of sympathetic stimulation upon saliva production?
Low volume
Thick
Mucus rich
66
What are the 4 main anatomical areas of the stomach?
Fundus
Body
Antrum
Pylorus
67
Where does most mixing/churning of food take place in the stomach?
Antrum
68
What is the substance produced when food mixes with gastric secretions?
Chyme
69
Name a substance which can be absorbed by the stomach!
Ethanol
70
Thickness of smooth muscle lining decreases distally in the stomach.
True/ False?
False
| Increasing thickness distally (antrum thickness greater than fundus thickness)
71
What occurs in retropulsion?
Peristaltic wave forces chyme against closed pyloric sphincter, so chyme bounces back and undergoes more mixing
72
Name 2 gastric factors promoting gastric emptying
Volume of chyme (larger volume increases motility due to distention)
Consistency of chyme (thinner liquid facilitates emptying)
73
Which 2 duodenal factors delay gastric emptying?
Enterogastric reflex
Release of enterogastrones
*An enterogastrone is any substance in the lower gastrointestinal tract which opposes the forward motion of the contents of chyme when exposed to lipids
74
What is the enterogastric reflex?
Duodenum signals to stomach that it has enough chyme so slow down emptying/ peristaltic contraction
75
What is the effect of enterogastrones on gastric emptying?
CCK and secretin release from duodenum inhibit stomach contraction
76
Where is the pyloric gland area located?
Antrum
77
Where is the oxyntic mucosa area located?
Fundus and Body
78
Which cells are contained in the pyloric gland area?
D cells
| G cells
79
What do D cells secrete?
Somatostatin
80
What do G cells secrete?
Gastrin
81
Which cells are contained in the oxyntic mucosa?
Parietal cells
Enterochromaffin-like cells
Chief cells
82
What do ECL (Enterochromaffin-like cells) cells secrete?
Histamine
83
What do parietal cells secrete?
HCl
| Intrinsic factor
84
What do chief cells secrete?
Pepsinogen
85
What does autocatalytic mean with regards to pepsinogen and pepsin?
Pepsin formation triggers further pepsin formation from pepsinogen
86
What is the role of intrinsic factor in the oxyntic mucosa?
Binds vitamin B12
87
What is the role of histamine in the oxyntic mucosa?
Stimulates HCl secretion
88
What is the role of gastrin in the pyloric gland area?
Stimulates HCl secretion
89
What is the role of somatostatin in the pyloric gland area?
Inhibits HCl secretion
90
Describe how parietal cells produce HCl!
In parietal cells carbonic anhydrase combines CO2 and H2O to form H+ and HCO3.
HCO3 is transported out of the cell in exchange for Cl via an antiporter.
H+ is secreted via a proton pump.
H+ and Cl combine to form HCl.
91
What are secretagogues?
Substances promoting secretion of HCl (gastrin, ACh, histamine)
92
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
93
What are the 3 phases of gastric secretion?
Cephalic - chewing and swallowing - gastric secretion
Gastric - distension - gastric secretion
Intestinal - stomach empties - gastric secretion inhibited
94
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 (gastrin releasing peptide)
95
What is involved in the gastric phase?
Distention due to food causes mechanoreceptors to augment secretion
96
What is involved in the intestinal phase?
Gastric secretion is halted through secretin, CCK and somatostatin as the stomach empties
97
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
98
What are the two forms of starch?
Amylose
| Amylopectin
99
Amylose and amylopectin are branched chain molecules.
| True/ False?
False
| Amylose isn't but amylopectin is branched
100
Which type of bond links glucose monomers in amylose?
alpha-1,4
101
Which type of bonds link glucose monomers in amylopectin?
alpha-1,4
| alpha-1,6 for branched chain
102
Glycogen is a branched chain polysaccharide.
| True/ False?
True
103
Which type of bond links glucose monomers in glycogen?
alpha-1,4
| alpha-1,6
104
Name two oligosaccharides (disaccharides)!
Lactose
| Sucrose
105
Which monomers make up sucrose?
Glucose and fructose
106
Which monomers make up lactose?
Glucose and galactose
107
Which enzyme carries out luminal digestion of starch?
Alpha-amylase
108
What is starch broken down into in luminal digestion?
Oligosaccharides - e.g. maltose, lactose sucrose
109
Which enzymes carry out brush border digestion of maltose, lactose and sucrose?
Maltase
Lactase
Sucrase-isomaltase
110
What are oligosaccharides such as lactose, maltose and sucrose broken down into in brush border digestion?
Monosaccharides - e.g. glucose, fructose, galactose
111
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
112
Lactase can only break down lactose.
| True/ False?
True
113
How is isomaltase unique?
It is the only enzyme that can split the branching of alpha-1,6 linkages
114
What is lactose intolerance?
Inability to digest lactose, caused by lactase insufficiency
115
Absorption of monosaccharides involves entry via the basolateral membrane and exit via the apical membrane.
True/ False?
False
| Other way around!
116
What is meant by secondary active transport?
Transport either via cotransport or antiport
117
What are oligopeptides?
Dipeptides
Tripeptides
Some tetrapeptides
[products of protein digestion]
118
What denatures proteins in the stomach?
HCl
119
Which enzyme cleaves protein into peptides in the stomach?
Pepsin
120
Is pepsin essential for protein digestion?
No
121
What are the active enzymes that digest protein in the duodenum?
```
Trypsin
Chymotrypsin
Elastase
Procaroxypeptidase A
Procaroxypeptidase B
```
122
Where does most fat digestion take place?
Small intestine
123
Which enzyme cleaves off fatty acids from triglycerides in the stomach?
Gastric lipase
124
What is the main lipid digesting enzyme in the duodenum?
Pancreatic lipase
125
What do bile salts do to large lipid droplets?
Emulsify them into smaller droplets
126
Which enzyme acts as a cofactor for lipase to help it gain access to the triglyceride chain?
Colipase
127
What is a mixed micelle?
Emulsified fat globule containing monoglyceride, fatty acids, phospholipid, bile salt and cholesterol
128
How are short and medium -chain fatty acids absorbed into capillaries?
Exit basolateral membrane via diffusion
129
What happens to long-chain fatty acids and monoglycerides once in the enterocyte?
Resynthesised to triglyceride in the ER and incorporated into chylomicrons
130
What coats the cholesterol ester-triglyceride complex to form a chylomicron?
Apolipoprotein (apo-B48)
131
How does the chylomicron exit the enterocyte?
| Where does it go?
Exocytosis into the lymphatic system
132
Chylomicrons are cleaved by --- in muscle and adipose tissue.
Lipoprotein lipase
133
What carries the free fatty acids and glycerol released by chylomicron degradation?
Albumin
134
What does a chylomicron remnant consist of?
Cholesterol and phospholipid
135
Which protein allows cholesterol absorption?
NPC1L1 protein
136
How does the scaffold containing cholesterol bound to NPC1L1 move around the cell?
Via myosin runners
137
When calcium concentration is low, it is absorbed via Ca channels.
Which vitamin increases expression for these channels?
Vitamin D
138
Ferric iron can be absorbed by the enterocyte.
| True/ False?
False
| Must be converted to ferrous iron (Fe2)
139
What is the other mechanism (other than receptor transport) by which iron can be absorbed by the enterocyte?
Haem is taken up and degraded by haem oxidase
140
What is the storage form of iron called?
Ferratin
141
What are the ranges for normal BMI?
18.5-25
142
What are the ranges for BMI classed as overweight?
25-29
143
What are the ranges for BMI classed as obese?
30-39
144
What are the ranges for BMI classed as morbidly obese?
Greater than 40
145
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
146
Lesioning ventromedial hypothalamus causes leanness.
| True/ False?
False
| Lesioning ventromedial hypothalamus causes obesity
147
Which lesioning part of the hypothalamus causes leanness?
Lateral part
148
Define satiation!
Feeling of fullness during/ following a meal
149
Define satiety!
Period from end of one meal to beginning of next
150
What effects do satiation signals have during a meal?
Increased signals limit meal size
151
What is ghrelin?
A hunger signal - levels increase before a meal and decrease after a meal
152
Which 2 hormones report the "fat status" of fat stores to the brain?
Leptin
| Insulin
153
Levels of leptin and insulin increase in the blood as more fat is stored.
True/ False?
True
154
Reduced leptin mimics starvation.
| True/ False?
True
155
Name a drug that can be prescribed to tackle obesity!
Orlistat
156
How does Orlistat work?
Inhibits pancreatic lipase to decrease triglyceride absorption
157
Vomiting is due to stomach contraction.
| True/ False?
False
| Stomach, oesophagus + sphincters are relaxed
158
Which centre coordinates vomiting in the brainstem?
Vomiting centre (VC) in the medulla oblongata
159
Does nausea always cause vomiting?
No
160
Toxic materials stimulate enterochromaffin cells to release which mediator of vomiting?
5-HT (serotonin)
161
Which 3 stimulants stimulate the brainstem to act on the vomiting centre to initiate vomiting?
Toxins
Mechanical activity/ disease
Motion sickness
162
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
163
Place the parts of the small intestine in order from shortest to longest
Duodenum (0.25m)
Jejunum (2.5m)
Ileum (3m)
164
Which 3 components increase the surface area of the small intestine?
Circular folds
Villi
Microvilli
165
Where is gastrin secreted from?
G cells of stomach + duodenum
166
Where is CCK secreted from?
I cells of duodenum + jejunum
167
Where is secretin secreted from?
S cells of duodenum
168
Where is motilin secreted from?
M cells of duodenum + jejunum
169
Where is ghrelin secreted from?
Gr cells of stomach, small intestine + pancreas
170
Distention, gastrin, CCK, secretin + parasympathetic activity all enhance the secretion of intestinal juice.
True/ False?
True
171
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
172
Gastrin and CCK trigger the migrating motor complex.
| True/ False?
False
| Motilin triggers it; CCK and gastrin inhibit it
173
What does the aqueous salt solution released from pancreatic duct cells do?
Neutralises acidic chyme in the duodenum
174
Acid and chyme in duodenum stimulates/ inhibits the release of secretin.
This stimulates/ inhibits release of intestinal juice from pancreas.
Acid and chyme in duodenum stimulates the release of secretin.
This stimulates release of intestinal juice from pancreas.
175
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
176
Describe haustration!
Intermittent contraction of circular muscle in proximal colon at slow rate to allow contents to move but leave enough opportunity for reabsorption
177
Which nerve conveys efferents to cause either relaxation or contraction of the external anal sphincter?
Pudendal nerve
178
Reabsorption of water is largely driven by the reabsorption of which ion?
Sodium
179
Which mechanism is the most major in Na reabsorption in the post-prandial period in the jejunum?
Na-glucose and Na-amino acid cotransport
180
What is the effect of cAMP, cGMP and Ca2+ on NaCl absorption?
Reduce NaCl absorption
181
Where do epithelial Na channels (ENaC) mediate Na absorption?
Distal colon
182
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)
183
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)
```
184
What is the direction of blood flow in a liver lobule?
Inwardly through sinusoids towards the central vein
185
What is the direction of bile flow in a liver lobule?
Outwardly through canaliculi towards the bile duct
186
Canaliculi are formed by the basolateral membrane.
| True/ False?
False
| Canaliculi are formed by the apical membrane
187
Which membrane faces the space of Disse?
Basolateral membrane
188
Which 3 types of cell are located in the sinusoidal spaces?
Endothelial cells
Kuppfer cells
Stellate (Ito) cells
189
What is the function of endothelial cells in the sinusoidal space?
Fenestrated structure allows passage of solute, but not cells
190
What is the function of Kuppfer cells in the sinusoidal space?
Macrophages that remove bacterial matter and dead RBCs
191
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
192
Most bile is secreted by bile duct cells.
| True/ False?
False
| Most is secreted by the liver
193
Most of the bile entering the duodenum is reabsorbed in the terminal ileum.
True/ False?
True
