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S2 Case 2 - Diarrhoea > Large Intestine, Constipation, Diarrhoea + Lactose Intolerance > Flashcards

Large Intestine, Constipation, Diarrhoea + Lactose Intolerance Flashcards

(71 cards)

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1
Q

What does the longitudinal muscle do?

A

Lumen becomes shorter + fatter
= facilitate movement of food

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2
Q

What does the circular muscle do?

A

Narrower + longer

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3
Q

What does the muscularis mucosae do?

A

Change in absorptive + secretory area of mucosa

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4
Q

What are the 2 plexuses in enteric nervous system?

A

Myenteric
Submucosa

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5
Q

What is the enteric nervous system comprised of?

A

Sensory neurons then interneurons then effector neurons

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6
Q

What are the sensory neurons?

A

Mechanoreceptors, chemoreceptors + thermoreceptors

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7
Q

What are the interneurons?

A

Co-ordinate reflexes + motor programs

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8
Q

What are the effector neurons?

A

Excitatory + inhibitory motor neurons

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9
Q

What is involved in autonomic innervation of GI?

A

Parasympathetic + sympathetic

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10
Q

What are the excitatory influences of parasympathetic?

A

Increase gastric secretion, blood flow + smooth muscle contraction

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11
Q

What are the inhibitory influences of parasympathetic?

A

Relaxation of sphincters
Receptive relaxation of stomach

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12
Q

What does the parasympathetic not have?

A

Discrete ganglia = found on target organ

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13
Q

What does the sympathetic do?

A

Inhibitory influences
= decrease motility, secretion + blood flow

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14
Q

What is functionally more important parasympathetic or sympathetic?

A

Parasympathetic

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15
Q

What is smooth muscle in GI tract capable of + why?

A

Spontaneous contraction
= contract as one big cell
= joined by gap junctions

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16
Q

What is spontaneous activity of smooth muscle in GI tract modulated by?

A

Intrinsic (enteric) + extrinsic (autonomic) nervous system
Hormones

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17
Q

What does spontaneous electrical activity occur as?

A

Slow waves

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18
Q

What are slow waves driven by?

A

Interstitial cells of Cajal (ICCs)
= pacemaker cells

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19
Q

Where are ICCs located?

A

Between longitudinal + circular muscle layers in submucosa

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20
Q

What do slow waves determine?

A

Basic electrical rhythm

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21
Q

What does it depend on that slow waves reach threshold?

A

Neuronal stimuli
Hormonal stimuli
Mechanical stimuli

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22
Q

What is peristalsis?

A

Series of wave-like muscle contractions that move food through digestive-tract triggered by distention of gut wall
Involves longitudinal muscle layers

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23
Q

What is segmentation?

A

Rhythmic contraction of circular muscle layer that mix + divide luminal contents

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24
Q

What do circular muscle do?

A

Make lumen smaller = squeeze food = break large bits apart

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25
What is the absorption of water driven by?
Transport of Na+ Passive process
26
What is diarrhoea defined as in terms of water loss?
Excess of 500 ml per day
27
How may water move?
Paracellularly = through tight junction Transcellularly = through cell
28
Describe Na+/glucose co-transport mechanism for H2O movement
Electrogenic Small intestine
29
Describe Na+/amino acid co-transport mechanism for H2O movement
Electrogenic Small intestine
30
Describe Na+/H+ co-transport mechanism for H2O movement
Electroneutral (powered by presence of bicarbonate) Duodenum + jejunum
31
Describe parallel Na+/H+ + Cl-/HCO3- co-transport mechanism for H2O movement
Electroneutral Ileum + colon
32
Describe epithelial Na+ channel mechanism for H2O movement
Electrogenic Distal colon
33
Why is something electrogenic?
Na+ goes to blood = makes blood more positive = creates electrical charge
34
What is something electroneutral?
Na+ goes in H+ comes out = NO change in electrical charge
35
When is Cl- also reabsorbed?
IN ALL OF THEM
36
Describe Cl- secretion
Occurs at basal rate From crypt cells Important in diarrhoea
37
What happens in basolateral membrane mechanism of Cl- secretion?
Na+, K+ + Cl- enter by co-transport Cl- enters lumen through CFTR channel Na+ reabsorbed Cl- attracts Na+ via paracellular = H2O follows
38
What are CRTF channels normally?
Closed
39
What are CFTR activated by?
Bacterial enterotoxins Hormones + neurotransmitters Immune cell products Laxatives
40
What is the role of CFTR in diarrhoea?
Activation = generation of 2nd messengers
41
What are the 2nd messengers?
cAMP cGMP Ca2+
42
What is secretory diarrhoea?
Secretion of Na+, Cl- + H2O
43
What is the 1st cause of secretory diarrhoea?
Excessive secretion = caused by E.coli
44
How does cholera cause secretory diarrhoea (excessive secretion)?
GDP goes to GTP = subunit dissociates Cholera toxin inhibits activity of GTPase activity of subunit
45
What may also cause secretory diarrhoea (excessive secretion)?
Increased activity in adenylate cyclase Increased conc of cAMP cAMP stimulates CFTR Hypersecretion of Cl-, Na+ + H2O
46
What is the 2nd cause of secretory diarrhoea?
Impaired absorbance of NaCl = caused by congenital defects
47
What is 3rd cause of secretory diarrhoea?
Non-absorbable/ poorly absorbable solutes = lactose intolerance
48
What is 4th cause of secretory diarrhoea?
Hypermotility = excessive peristalsis of GI
49
What are the consequences of diarrhoea?
Dehydration Metabolic acidosis Hypokalaemia
50
What is the treatment process for diarrhoea?
Maintain fluid balance (1st) Anti-infective agents (if appropriate) Anti-motility agents
51
How does rehydration therapy work?
2 Na+ bind Affinity for glucose increases Na+ + glucose translocate to intracellular 2 Na+ dissociate, affinity for glucose falls Glucose dissociates Cycle repeated
52
What do anti-motility drugs do?
Decrease motility in gut
53
What can opiates do?
Anti-diarrhoeal activity = inhibit enteric neurons = decrease peristalsis, increase segmentation
54
What are the major opioids used in diarrhoea?
Codeine Diphenoxylate Loperamide - 1st choice Atropine
55
What are problems with codeine?
NOT very selective = CNS activation
56
What are the problems with atropine?
Anti-muscarinic = decrease parasympathetic activity = decrease motility BUT not selective
57
Why is loperamide 1st choice?
Relatively selective to GI tract Increases segmentation, decreases peristalsis
58
What is lactose intolerance?
Lactase deficiency
59
What is primary lactase deficiency?
Lack of lactase persistence allele
60
What is secondary lactase deficiency?
Damage to proximal small intestine
61
What is congenital lactase deficiency?
Rare autosomal recessive disease = from birth
62
When does hypolactasia cause a problem?
Lactose-containing food is consumed
63
Describe process of lactose intolerance
NOT digested in small intestine = goes to large intestine = bacteria convert it to H gas + fatty acids = attract H2O
64
How is diagnosis done for lactose intolerance?
Diet observation
65
How is lactose intolerance treated?
Reduction or elimination in lactose-containing food
66
What are the causes of constipation?
Neurogenic disorders of large intestine Abdominal muscle weakness Diet poor of fibre Aging
67
Why do neurogenic disorders of large intestine cause constipation?
Reduce peristalsis eg. IBD, cancer
68
How do you treat constipation? Changes in lifestyle
More H2O, less alcohol Increase activity Improve toilet routine = keep tp regular time
69
What drugs can be used to treat constipation?
Laxatives Antiemetics
70
What laxatives can be used to treat constipation?
Bulk laxatives Osmotic laxatives Faecal softeners Stimulant laxatives
71
Why can antiemtics be used to treat constipation?
Increase motility + gastric emptying

S2 Case 2 - Diarrhoea (12 decks)

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