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Physiology Flashcards

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1
Q

Function of the mouth and oropharynx

A
  • chops and lubricates food, starts carbohydrate digestion
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2
Q

Function of the oesophagus

A

-propels food to stomach

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3
Q

Function of the stomach

A
  • stores/churns food, continues carbohydrate,
  • initiates protein digestion,
  • regulates delivery of chyme to duodenum
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4
Q

Function of the small intestine

A

-principal site of digestion and absorption of nutrients

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5
Q

Function of the Large intestine

A

-Colon reabsorbs fluids and electrolytes, stores faecal matter before delivery to rectum

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6
Q

Function of the rectum and anus

A
  • regulated expulsion of faeces
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7
Q

Name the accessory structures of the GI tract

A
  • salivary glands
  • pancreas
  • the liver and gall bladder
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8
Q

What does aboral mean?

A
  • contents of GI track travel towards the anus
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9
Q

What is the name given to the movement in the opposite direction of aboral?

A
  • oral movement
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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.

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11
Q

What are the 4 main structures/linings of the Digestive tract?

A
  • mucosa
  • submucosa
  • muscular externa
  • serosa
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12
Q

What are the 4 major functions of the alimentary canal?

A
  • motility
  • secretion
  • digestion
  • absorption
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13
Q

What happens to the lumen of the GI tract when the circular muscle contracts?

A
  • lumen becomes narrower and longer
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14
Q

What happens to the lumen of the GI tract when the longitudinal muscle contracts?

A
  • intestine becomes shorter and fatter
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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

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16
Q

what creates spontaneous activity in smooth muscle cells in the Gi tract?

A
  • specialised pacemaker cells
  • intrinsic (enteric)
  • extrinsic (autonomic)
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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
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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
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19
Q

What 3 factors effect the threshold requirements?

A
  • neuronal stimuli
  • Hormonal stimuli
  • Mechanical stimuli
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20
Q

Where are the post-ganglionic parasympathetic cells located?

A
  • within the walls of the enteric nervous system
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21
Q

What is the excitatory influences of parasympathetic nerves?

A
  • increased gastric secretion
  • increased blood flow
  • smooth muscle contraction
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22
Q

The sympathetic influence on GI tract is functionally less important than parasympathetic?
true/false?

A
  • true
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23
Q

When is the preganglionic fibres of the sympathetic nerves located in the GI tract?

A
  • prevertebral ganglia
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24
Q

Excitatory influences the sympathetic nerves on the GI tract?

A
  • increased sphincter tone
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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
GI
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