Physiology Flashcards
1
Q
Function of the mouth and oropharynx
A
- chops and lubricates food, starts carbohydrate digestion
2
Q
Function of the oesophagus
A
-propels food to stomach
3
Q
Function of the stomach
A
- stores/churns food, continues carbohydrate,
- initiates protein digestion,
- regulates delivery of chyme to duodenum
4
Q
Function of the small intestine
A
-principal site of digestion and absorption of nutrients
5
Q
Function of the Large intestine
A
-Colon reabsorbs fluids and electrolytes, stores faecal matter before delivery to rectum
6
Q
Function of the rectum and anus
A
- regulated expulsion of faeces
7
Q
Name the accessory structures of the GI tract
A
- salivary glands
- pancreas
- the liver and gall bladder
8
Q
What does aboral mean?
A
- contents of GI track travel towards the anus
9
Q
What is the name given to the movement in the opposite direction of aboral?
A
- oral movement
10
Q
Define chyme
A
-the pulpy acidic fluid which passes from the stomach to the small intestine, consisting of gastric juices and partly digested food.
11
Q
What are the 4 main structures/linings of the Digestive tract?
A
- mucosa
- submucosa
- muscular externa
- serosa
12
Q
What are the 4 major functions of the alimentary canal?
A
- motility
- secretion
- digestion
- absorption
13
Q
What happens to the lumen of the GI tract when the circular muscle contracts?
A
- lumen becomes narrower and longer
14
Q
What happens to the lumen of the GI tract when the longitudinal muscle contracts?
A
- intestine becomes shorter and fatter
15
Q
What junctions are couple to smooth muscle in GI tract?
A
- gap junctions
- allows all of the smooth muscle cells to contract in a synchronous wave
16
Q
what creates spontaneous activity in smooth muscle cells in the Gi tract?
A
- specialised pacemaker cells
- intrinsic (enteric)
- extrinsic (autonomic)
17
Q
What is the importance of the interstitial cells of cajal (ICCs)
A
- pacemaker cells
- located between muscle layers
- drive slow waves that occur in smooth muscle cells
- Determines the frequency, direction and velocity of rhythmic contractions
18
Q
Explain the relationship between thresholds and contraction in the intestines.
A
- contraction only occurs if the slow wave amplitude is sufficient to reach a threshold
- force is related to number of action potentials discharged
19
Q
What 3 factors effect the threshold requirements?
A
- neuronal stimuli
- Hormonal stimuli
- Mechanical stimuli
20
Q
Where are the post-ganglionic parasympathetic cells located?
A
- within the walls of the enteric nervous system
21
Q
What is the excitatory influences of parasympathetic nerves?
A
- increased gastric secretion
- increased blood flow
- smooth muscle contraction
22
Q
The sympathetic influence on GI tract is functionally less important than parasympathetic?
true/false?
A
- true
23
Q
When is the preganglionic fibres of the sympathetic nerves located in the GI tract?
A
- prevertebral ganglia
24
Q
Excitatory influences the sympathetic nerves on the GI tract?
A
- increased sphincter tone
25
Name an example of a local reflex nerve in the GI tract?
- peristalsis
26
How is BMI calculated?
= weight (kg) /square of height (m)
27
Consequences of obesity?
- stroke
- respiratory disease
- heart disease
- osteoarthritis
- demential
- fatty liver
- diabetes
- cancer
28
Why is it hard to loose weight once you have gained it?
- Long-term obesity induces brain re-programming
- Your brain views the extra weight (fat) as
normal & dieting as threat to body survival
29
3 CNS influences on energy balance and body weight?
- behaviour
- ANS activity
- Neuroendocrine system
30
Define Satiation
sensation of fullness generated during a meal
31
Define Satiety
period of time between termination of one meal and
| the initiation of next
32
Define Adiposity
the state of being obese
33
What regulates output from the brain in regards to obesity?
- hypothalamus
34
Examples of satiation signals?
- cholecystokinin
- peptide YY
- Glucagon-like peptide 1
- oxyntomodulin
- obestatin
35
What is ghrelin
- a hunger signal
| - Increase in levels before meals and decreases after
36
What are the 2 hormones that report fat status to the brain?
- leptin (made from fat cells)
| - insulin (made from pancreatic beta cells)
37
What is hormone function in regards to obesity?
- inform brain (hypothalamus) to alter energy balance - eat less and increase energy burn
38
Reducing leptin does what____
- mimics starvation
| - causing unrestrained appetite
39
Biological roles of leptin?
- food intake/energy expenditure/fat depostion
- peripheral glucose homeostasis
- maintenance of immune system
- bone formation
40
What is an over the counter obesity drug and how does it work?
- Orlistat
| - reduces fat absorption
41
Define peristalsis
- a wave of relaxation followed by a contraction, usually in an aboral direction in the gut
42
Define segmentation in the GI tract
- segmentation - mixing or churning movements
| - rhythmic contractions of the circular muscle layer
43
Define colonic mass movement
- powerful sweeping contraction that forces faeces into the rectum
44
What occurs in the stomach?
- starting point of digestion of proteins
- continues carbohydrate digestion
- Mixing of food with gastric secretions to produce a semi-liquid liquid chyme
45
What are the 2 portions of the stomach and what is its role
- Orad stomach --> stores food
| - Caudad stomach --> propel semi-digested food
46
There is slow wave activity in the orad region of the stomach.
True or false
- FALSE
- there is no slow wave activity
- food is static
- continious weak tonic contractions
47
Why is it important that food is static in the orad region of the stomach?
- allows for carbohydrate partial digestion by salivary amylase
48
What occurs in the caudad region of the stomach?
- slow waves occur continuously
| - propelling contents towards pylorus to the duodenum
49
What controls the stomach emptying
- strength of antral wave, or pump, determines escape of chyme through pyloric sphincter
- proportional to the amount of chyme in the stomach
- the consistency of the chyme
50
What are examples of stimuli within the duodenum that drive neuronal and hormone responses?
- fat
- acid
- hypertonicity
- distension
51
What are the 3 parts of the small intestine?
- duodenum
- jejunum
- ileum
52
What is received at the small intestine?
- chyme from the stomach
- pancreatic juice from the pancreas
- bile from the liver and gall bladder
53
The name of the process by which chyme is mixed with digestive juices in the small intestine?
- segmentation
| - occurs after a meal
54
How is the small intestine adapted for absorption?
- circular folds of kerckring
- villi
- microvilli
- all increase the surface area
55
How many contractions per minute does the duodenum have?
- 12 per minute
| - 9 Per minute in the ileum
56
What are migrating motor complex (MMC)?
- Occurs between meals
- strong peristaltic contraction
- clears the small intestine of debris
- inhibited by feeding and vagal activity
57
Gastrin is secreted by the small intestine into blood, what is it?
- from g cells of gastric Antrum and duodenum
| - stimulated H+ Secretion by gastric parietal cells
58
Cholecystokinin (cck) is released from the small intestine into the blood, what is it?
- from I cells of the duodenum and jejunum
- released in response to mnoglycerides, fatty acids and amino acids
- stimulates the release of bile
- inhibits gastric emptying
59
Secretion of the small intestine lack digestive enzymes but contains_____
- mucus
| - aqueous salts for enzymatic digestion
60
What controls the secretions of the small intestine?
- distension
- gastrin
- CCK
- parasympathetic nerve - increases
- sympathetic nerve - decreases
61
What are the endocrine secretions of the pancreas?
- insulin and glucagon
| - secreted to blood
62
What are the exocrine secretions of the pancreas?
- digestive enzymes
| - secreted to the duodenum
63
What do the pancreatic duct cell secrete?
- alkaline fluid
- release into the duodenum
- neutralises acidic chyme entering the duodenum
64
What are the three phases of control of pancreatic secretion?
- cephalic
- gastric
- intestinal
65
what must carbohydrates be converted to, to allow absorption?
- carbohydrates must be converted to monosaccharides for absorption
66
Oligosaccharides are ____ membrane proteins?
- integral membrane proteins
67
How many substrates does lactase have?
- has one substrate
| - breaks lactose to glucose and galactose
68
Absorption of glucose and galactose are absorbed by _______ mediated by ______
- absorbed by secondary active transport mediated by SGLT1
69
Fructose is absorbed by______ mediated by____
- facilitated diffusion
| - mediated by GLUT5
70
Exit for all monosaccharides in the duodenum is mediated by____
- facilitated diffusion
| - by GLUT2
71
What is the large intestine compromised of?
- caecum and appendix
- colon
- rectum
- anal canal and anus
72
What are the divisions of the colon?
- ascending
- transverse
- descending
- sigmoid
73
Which part of the large intestine has thickened smooth muscle?
- internal anal sphincter
74
What is the name of the 'sac-like' bulges in the large intestine and what causes them?
- haustra
| - activity of the taeniae coli and circular muscle
75
What is the function of the caecum and appendix?
- no specialised function in humans
76
how is entry permitted into the caecum?
- gastroileal reflex in response to gastrin and CCK
77
What is obstructed during appendicitis?
- appendiceal orifice
78
What are the primary functions of the colon?
- absorption (Na+, Cl- and H20)
- absorption (fatty acids)
- secretion
- to store colonic contents
- periodically eliminate faces
79
Why does the large intestine absorb fatty acids?
- carbohydrates not absorbed by the small intestine are fermented by colonic flora to short chain fatty acids
80
The colon has villi to increase surface area
True or false?
- FALSE
| - the colon lacks vili, instead it has colonic folds and crypts, microvilli to increases area
81
What are the 3 sources of motility in the large intestine?
- haustratration
- peristaltic propulsive movements
- defaecation
82
What is haustration?
- movement of haustra
| - activity of the taeniae coli and circular muscle
83
Explain mass movement
- simultaneous contraction of large section of the circular muscle of the ascending and transverse colon
- triggered by a meal
84
Explain defaecation
- mass movement - rectum fills with faecal matter
- activation of rectal stretch receptors
- activation of afferents to brain/spinal cord
- relaxation or contraction of skeletal muscle of external anal spnicter
85
Gas released by the anus comes from where?
- swallowed air
- bacteria in the colon which attacks forms of carbohydrates that are indigestible to humans
- gas that is not absorbed by the large intestine
86
Name drugs that can be used in IBS?
- Linaclotide (peptide drug)
| - amitriptyline
87
Name drugs that can be used in IBD?
- Glucocorticoids
| - aminosalicylates
88
What are ingested lipids compromised of?
- fats/oils
- phospholipids
- cholesterol
- fatty acids
89
What must fats be converted to?
- emulsion of small oil droplets suspended in water
90
What causes emulsification?
- mouth
- stomach (gastric curing)
- small intestine (segmentation and peristalsis, mixing with pancreatic and biliary secretions)
91
How are emulsion droplets stabilised?
- addition of a coat of amphiphilic molecules that form a surface layer on the droplets
92
What are TAGs?
- triacylglyerol
- 1 glycerol molecule
- 3 fatty acids
93
How are TAGs digested?
- as they are extremely hydrophobic they are hydrolysed by water and gastric lipase
- form diacylglyerol and free fatty acid
94
Where does the lingual phase of digestion occur?
- the mouth
95
Short and medium chain fatty acids are absorbed by the stomach, but long chain fatty acids are not
True or false?
- true
96
Where does the intestinal phase of digestion occur?
- duodenum
| - by pancreatic (TAG) lipases
97
Where is pancreatic lipase secreted from in response to what?
- secreted from acinar cells
| - in response to CCK
98
Gastric lipase breaks triacylglyercol to what?
- diacylglycerol + free fatty acid
99
Pancreatic lipase breaks triacylglyerol to what?
- 2-monoacylglyerol + 2 free fatty acids
100
What is the role and characteristics of bile salts?
- released in the duodenum in bile from the gall bladder in response to CCK
- Help emulsify large lipid droplets to small droplets
- amphipathic
- increase the surface area for attack by pancreatic lipase - but block for TAG
101
What does a failure to secrete bile salts result in?
- lipid malabsorption
| - secondary vitamin deficiency
102
What is colipase?
- amphipathic polypeptide
| - binds to bile salts and lipase allowing access by the latter to try and di- acylglycerols
103
What is procolipase activated by? and what does it become?
- activate by: trypsin
| - becomes : colipase
104
How do small/medium fatty acid chains enter the enterocyte?
- fatty acid translocases
| - transport proteins
105
What happens to the long chain fatty acids and monoglycerides during lipid absorption?
- resynthesized to triglycerides
| - incorporated into chylomicrons
106
How is cholesterol absorbed?
- NPC1L1 proteins
107
Where are newly formed chylomicrons sent?
- to the lymph
108
What is calcium absorption regulated by?
- 1,25-dihydroxyvitamin D3
| - aka calcitriol
109
What would a deficiency in iron cause?
- microcytic anaemia
110
What would happen due to an excess of iron?
- toxic
| - accumulation in the liver, pancreas and heart
111
What state is most dietary iron?
- Fe3+
| - oxidised form
112
What form of iron can be absorbed across the apical membrane of the duodenal enterocytes?
- reduced form
| - Fe2+
113
What does Fe2+ bind to in the stomach?
- gastroferrin
114
What oxidises Fe2+
Hephaestin
115
What is the main transport protein of iron in the body?
- transferrin
116
How is vitamin B12 obtained from the diet?
- ingested bound to protein
- stomach releases the b12
- haptocorin secreted in saliva binds to the b12
- digested by pancreatic proteases
- b12 absorbed by terminal ileum
117
How are fat soluble vitamins absorbed?
- they are incorporated into mixed micelles with other lipids and bile acids in the lumen of the small intestine
- enter the enterocyte largely by diffusion.
118
What digestion occurs in the stomach?
- continuation of carbohydrate digestion (salivary amylase)
| - start of protein digestion (pepsin and HCl)
119
Explain retropulsion?
- mixes gastric contents reducing chyme to small particles to pass through the pylorus
120
What are the duodenal factors that influence stomach emptying?
- neuronal responses --> enterogastric reflex
| - hormonal responses --> release of enterogastrones (cck)
121
D cells secrete?
- somatostatin
122
G cell secrete?
- gastrin
123
Enterochromaffin-like cells secrete?
- histamine
124
Function of HCl?
- activates pepsinogen to pepsin
- kills microorganisms
- denatures proteins
125
What is an intrinsic factor for?
- binds vitamin B12
126
What is gastroferrin
- binds Fe2+
127
What does histamine do?
- increases HCl secretion
128
Explain HCl secretion by parietal cells?
- CO2 enters parietal cells from basolateral end
- combines with water to produce H2CO3
- H2CO3 --> HCO3- + H+
- HCO3 leaves cell and CL- enters
- H+ leaves through proton pump and K+ enters
- K+ leaves through K channel
- Cl- leaves through Cl- channel
- Cl and H+ Combine in stomach lumen
129
What are the 3 phases of gastric acid secretion?
- cephalic phase (head)
- gastric phase
- intestinal phase
130
Absorption of water is a ________ process?
- passive process
131
Absroption of water is driven by the transport of ______
- solutes
132
Define diarrhoea in terms of fluid loss?
- loss of fluid and solutes in excess of 500ml/day
133
Where does Na+/H+ transport occur?
- ileum and proximal colon
134
Where does Na+/glucose co-transport occur?
- jejunum
135
CFTR closed = ____ secretions
-little
136
What causes diarrhoea?
- impaired absorption of Na+
- no absorption of solutes
- hypermobility
137
What does nausea involve?
- pallor
- sweating
- salivation
- perisalsis in opposite direction
138
Define retching?
- rhythmic reverse peristalsis of the stomach and oesophagus
| - dry - no efflux of vomitis
139
Define vomiting?
- forecful expulsion of gastric contents out of the mouth
140
Explain the pathway of vomiting
- forceful inspiration, closure of rima glottiddis
- relaxation of LOS
- Contraction of diaphragm
- opening of UOS
- ejection of gastric contents
141
Where is the vomiting centre located?
- medulla of the brainstem
142
What are the consequences of severe vomiting?
- dehydration
- loss of electolytes
- hypokakaemia
- rare --> mallory weiss tear
143
Ondanestron is what class of anti-emetic drug?
- 5-HT3 receptor antagonist
| - supress chemo side effects
144
Hyosine is what class of anti-emetic drug?
muscarininc acetylcholie receptor antagonist
| - used for motionsickness
145
Cyclizine is what class of anti-emetic drug?
- histamine H1 receptor antagonist
- motionsickness
- can cause drowsiness
146
Domperiadone is what class of anti-emetic drug?
- used fr drug induced vomiting
| - not effective for motionsickness
