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Physiology Flashcards

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
Q

Name an example of a local reflex nerve in the GI tract?

A
  • peristalsis
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26
Q

How is BMI calculated?

A

= weight (kg) /square of height (m)

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27
Q

Consequences of obesity?

A
  • stroke
  • respiratory disease
  • heart disease
  • osteoarthritis
  • demential
  • fatty liver
  • diabetes
  • cancer
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28
Q

Why is it hard to loose weight once you have gained it?

A
  • Long-term obesity induces brain re-programming
  • Your brain views the extra weight (fat) as
    normal & dieting as threat to body survival
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29
Q

3 CNS influences on energy balance and body weight?

A
  • behaviour
  • ANS activity
  • Neuroendocrine system
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30
Q

Define Satiation

A

sensation of fullness generated during a meal

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31
Q

Define Satiety

A

period of time between termination of one meal and

the initiation of next

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32
Q

Define Adiposity

A

the state of being obese

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33
Q

What regulates output from the brain in regards to obesity?

A
  • hypothalamus
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34
Q

Examples of satiation signals?

A
  • cholecystokinin
  • peptide YY
  • Glucagon-like peptide 1
  • oxyntomodulin
  • obestatin
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35
Q

What is ghrelin

A
  • a hunger signal

- Increase in levels before meals and decreases after

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36
Q

What are the 2 hormones that report fat status to the brain?

A
  • leptin (made from fat cells)

- insulin (made from pancreatic beta cells)

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37
Q

What is hormone function in regards to obesity?

A
  • inform brain (hypothalamus) to alter energy balance - eat less and increase energy burn
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38
Q

Reducing leptin does what____

A
  • mimics starvation

- causing unrestrained appetite

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39
Q

Biological roles of leptin?

A
  • food intake/energy expenditure/fat depostion
  • peripheral glucose homeostasis
  • maintenance of immune system
  • bone formation
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40
Q

What is an over the counter obesity drug and how does it work?

A
  • Orlistat

- reduces fat absorption

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41
Q

Define peristalsis

A
  • a wave of relaxation followed by a contraction, usually in an aboral direction in the gut
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42
Q

Define segmentation in the GI tract

A
  • segmentation - mixing or churning movements

- rhythmic contractions of the circular muscle layer

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43
Q

Define colonic mass movement

A
  • powerful sweeping contraction that forces faeces into the rectum
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44
Q

What occurs in the stomach?

A
  • starting point of digestion of proteins
  • continues carbohydrate digestion
  • Mixing of food with gastric secretions to produce a semi-liquid liquid chyme
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45
Q

What are the 2 portions of the stomach and what is its role

A
  • Orad stomach –> stores food

- Caudad stomach –> propel semi-digested food

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46
Q

There is slow wave activity in the orad region of the stomach.

True or false

A
  • FALSE
  • there is no slow wave activity
  • food is static
  • continious weak tonic contractions
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47
Q

Why is it important that food is static in the orad region of the stomach?

A
  • allows for carbohydrate partial digestion by salivary amylase
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48
Q

What occurs in the caudad region of the stomach?

A
  • slow waves occur continuously

- propelling contents towards pylorus to the duodenum

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49
Q

What controls the stomach emptying

A
  • 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
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50
Q

What are examples of stimuli within the duodenum that drive neuronal and hormone responses?

A
  • fat
  • acid
  • hypertonicity
  • distension
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51
Q

What are the 3 parts of the small intestine?

A
  • duodenum
  • jejunum
  • ileum
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52
Q

What is received at the small intestine?

A
  • chyme from the stomach
  • pancreatic juice from the pancreas
  • bile from the liver and gall bladder
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53
Q

The name of the process by which chyme is mixed with digestive juices in the small intestine?

A
  • segmentation

- occurs after a meal

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54
Q

How is the small intestine adapted for absorption?

A
  • circular folds of kerckring
  • villi
  • microvilli
  • all increase the surface area
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55
Q

How many contractions per minute does the duodenum have?

A
  • 12 per minute

- 9 Per minute in the ileum

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56
Q

What are migrating motor complex (MMC)?

A
  • Occurs between meals
  • strong peristaltic contraction
  • clears the small intestine of debris
  • inhibited by feeding and vagal activity
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57
Q

Gastrin is secreted by the small intestine into blood, what is it?

A
  • from g cells of gastric Antrum and duodenum

- stimulated H+ Secretion by gastric parietal cells

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58
Q

Cholecystokinin (cck) is released from the small intestine into the blood, what is it?

A
  • 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
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59
Q

Secretion of the small intestine lack digestive enzymes but contains_____

A
  • mucus

- aqueous salts for enzymatic digestion

60
Q

What controls the secretions of the small intestine?

A
  • distension
  • gastrin
  • CCK
  • parasympathetic nerve - increases
  • sympathetic nerve - decreases
61
Q

What are the endocrine secretions of the pancreas?

A
  • insulin and glucagon

- secreted to blood

62
Q

What are the exocrine secretions of the pancreas?

A
  • digestive enzymes

- secreted to the duodenum

63
Q

What do the pancreatic duct cell secrete?

A
  • alkaline fluid
  • release into the duodenum
  • neutralises acidic chyme entering the duodenum
64
Q

What are the three phases of control of pancreatic secretion?

A
  • cephalic
  • gastric
  • intestinal
65
Q

what must carbohydrates be converted to, to allow absorption?

A
  • carbohydrates must be converted to monosaccharides for absorption
66
Q

Oligosaccharides are ____ membrane proteins?

A
  • integral membrane proteins
67
Q

How many substrates does lactase have?

A
  • has one substrate

- breaks lactose to glucose and galactose

68
Q

Absorption of glucose and galactose are absorbed by _______ mediated by ______

A
  • absorbed by secondary active transport mediated by SGLT1
69
Q

Fructose is absorbed by______ mediated by____

A
  • facilitated diffusion

- mediated by GLUT5

70
Q

Exit for all monosaccharides in the duodenum is mediated by____

A
  • facilitated diffusion

- by GLUT2

71
Q

What is the large intestine compromised of?

A
  • caecum and appendix
  • colon
  • rectum
  • anal canal and anus
72
Q

What are the divisions of the colon?

A
  • ascending
  • transverse
  • descending
  • sigmoid
73
Q

Which part of the large intestine has thickened smooth muscle?

A
  • internal anal sphincter
74
Q

What is the name of the ‘sac-like’ bulges in the large intestine and what causes them?

A
  • haustra

- activity of the taeniae coli and circular muscle

75
Q

What is the function of the caecum and appendix?

A
  • no specialised function in humans
76
Q

how is entry permitted into the caecum?

A
  • gastroileal reflex in response to gastrin and CCK
77
Q

What is obstructed during appendicitis?

A
  • appendiceal orifice
78
Q

What are the primary functions of the colon?

A
  • absorption (Na+, Cl- and H20)
  • absorption (fatty acids)
  • secretion
  • to store colonic contents
  • periodically eliminate faces
79
Q

Why does the large intestine absorb fatty acids?

A
  • carbohydrates not absorbed by the small intestine are fermented by colonic flora to short chain fatty acids
80
Q

The colon has villi to increase surface area

True or false?

A
  • FALSE

- the colon lacks vili, instead it has colonic folds and crypts, microvilli to increases area

81
Q

What are the 3 sources of motility in the large intestine?

A
  • haustratration
  • peristaltic propulsive movements
  • defaecation
82
Q

What is haustration?

A
  • movement of haustra

- activity of the taeniae coli and circular muscle

83
Q

Explain mass movement

A
  • simultaneous contraction of large section of the circular muscle of the ascending and transverse colon
  • triggered by a meal
84
Q

Explain defaecation

A
  • 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
Q

Gas released by the anus comes from where?

A
  • 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
Q

Name drugs that can be used in IBS?

A
  • Linaclotide (peptide drug)

- amitriptyline

87
Q

Name drugs that can be used in IBD?

A
  • Glucocorticoids

- aminosalicylates

88
Q

What are ingested lipids compromised of?

A
  • fats/oils
  • phospholipids
  • cholesterol
  • fatty acids
89
Q

What must fats be converted to?

A
  • emulsion of small oil droplets suspended in water
90
Q

What causes emulsification?

A
  • mouth
  • stomach (gastric curing)
  • small intestine (segmentation and peristalsis, mixing with pancreatic and biliary secretions)
91
Q

How are emulsion droplets stabilised?

A
  • addition of a coat of amphiphilic molecules that form a surface layer on the droplets
92
Q

What are TAGs?

A
  • triacylglyerol
  • 1 glycerol molecule
  • 3 fatty acids
93
Q

How are TAGs digested?

A
  • as they are extremely hydrophobic they are hydrolysed by water and gastric lipase
  • form diacylglyerol and free fatty acid
94
Q

Where does the lingual phase of digestion occur?

A
  • the mouth
95
Q

Short and medium chain fatty acids are absorbed by the stomach, but long chain fatty acids are not

True or false?

A
  • true
96
Q

Where does the intestinal phase of digestion occur?

A
  • duodenum

- by pancreatic (TAG) lipases

97
Q

Where is pancreatic lipase secreted from in response to what?

A
  • secreted from acinar cells

- in response to CCK

98
Q

Gastric lipase breaks triacylglyercol to what?

A
  • diacylglycerol + free fatty acid
99
Q

Pancreatic lipase breaks triacylglyerol to what?

A
  • 2-monoacylglyerol + 2 free fatty acids
100
Q

What is the role and characteristics of bile salts?

A
  • 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
Q

What does a failure to secrete bile salts result in?

A
  • lipid malabsorption

- secondary vitamin deficiency

102
Q

What is colipase?

A
  • amphipathic polypeptide

- binds to bile salts and lipase allowing access by the latter to try and di- acylglycerols

103
Q

What is procolipase activated by? and what does it become?

A
  • activate by: trypsin

- becomes : colipase

104
Q

How do small/medium fatty acid chains enter the enterocyte?

A
  • fatty acid translocases

- transport proteins

105
Q

What happens to the long chain fatty acids and monoglycerides during lipid absorption?

A
  • resynthesized to triglycerides

- incorporated into chylomicrons

106
Q

How is cholesterol absorbed?

A
  • NPC1L1 proteins
107
Q

Where are newly formed chylomicrons sent?

A
  • to the lymph
108
Q

What is calcium absorption regulated by?

A
  • 1,25-dihydroxyvitamin D3

- aka calcitriol

109
Q

What would a deficiency in iron cause?

A
  • microcytic anaemia
110
Q

What would happen due to an excess of iron?

A
  • toxic

- accumulation in the liver, pancreas and heart

111
Q

What state is most dietary iron?

A
  • Fe3+

- oxidised form

112
Q

What form of iron can be absorbed across the apical membrane of the duodenal enterocytes?

A
  • reduced form

- Fe2+

113
Q

What does Fe2+ bind to in the stomach?

A
  • gastroferrin
114
Q

What oxidises Fe2+

A

Hephaestin

115
Q

What is the main transport protein of iron in the body?

A
  • transferrin
116
Q

How is vitamin B12 obtained from the diet?

A
  • 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
Q

How are fat soluble vitamins absorbed?

A
  • 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
Q

What digestion occurs in the stomach?

A
  • continuation of carbohydrate digestion (salivary amylase)

- start of protein digestion (pepsin and HCl)

119
Q

Explain retropulsion?

A
  • mixes gastric contents reducing chyme to small particles to pass through the pylorus
120
Q

What are the duodenal factors that influence stomach emptying?

A
  • neuronal responses –> enterogastric reflex

- hormonal responses –> release of enterogastrones (cck)

121
Q

D cells secrete?

A
  • somatostatin
122
Q

G cell secrete?

A
  • gastrin
123
Q

Enterochromaffin-like cells secrete?

A
  • histamine
124
Q

Function of HCl?

A
  • activates pepsinogen to pepsin
  • kills microorganisms
  • denatures proteins
125
Q

What is an intrinsic factor for?

A
  • binds vitamin B12
126
Q

What is gastroferrin

A
  • binds Fe2+
127
Q

What does histamine do?

A
  • increases HCl secretion
128
Q

Explain HCl secretion by parietal cells?

A
  • 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
Q

What are the 3 phases of gastric acid secretion?

A
  • cephalic phase (head)
  • gastric phase
  • intestinal phase
130
Q

Absorption of water is a ________ process?

A
  • passive process
131
Q

Absroption of water is driven by the transport of ______

A
  • solutes
132
Q

Define diarrhoea in terms of fluid loss?

A
  • loss of fluid and solutes in excess of 500ml/day
133
Q

Where does Na+/H+ transport occur?

A
  • ileum and proximal colon
134
Q

Where does Na+/glucose co-transport occur?

A
  • jejunum
135
Q

CFTR closed = ____ secretions

A

-little

136
Q

What causes diarrhoea?

A
  • impaired absorption of Na+
  • no absorption of solutes
  • hypermobility
137
Q

What does nausea involve?

A
  • pallor
  • sweating
  • salivation
  • perisalsis in opposite direction
138
Q

Define retching?

A
  • rhythmic reverse peristalsis of the stomach and oesophagus

- dry - no efflux of vomitis

139
Q

Define vomiting?

A
  • forecful expulsion of gastric contents out of the mouth
140
Q

Explain the pathway of vomiting

A
  • forceful inspiration, closure of rima glottiddis
  • relaxation of LOS
  • Contraction of diaphragm
  • opening of UOS
  • ejection of gastric contents
141
Q

Where is the vomiting centre located?

A
  • medulla of the brainstem
142
Q

What are the consequences of severe vomiting?

A
  • dehydration
  • loss of electolytes
  • hypokakaemia
  • rare –> mallory weiss tear
143
Q

Ondanestron is what class of anti-emetic drug?

A
  • 5-HT3 receptor antagonist

- supress chemo side effects

144
Q

Hyosine is what class of anti-emetic drug?

A

muscarininc acetylcholie receptor antagonist

- used for motionsickness

145
Q

Cyclizine is what class of anti-emetic drug?

A
  • histamine H1 receptor antagonist
  • motionsickness
  • can cause drowsiness
146
Q

Domperiadone is what class of anti-emetic drug?

A
  • used fr drug induced vomiting

- not effective for motionsickness

GI (36 decks)

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