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GI- Week 4 & 5 > Physiology & Pharmacology of Large intestine > Flashcards

Physiology & Pharmacology of Large intestine Flashcards

1
Q

Gastro-ileal reflex is stimulated by gastric _. It involves the opening of the _ valve.

A

Distension

Ileo-cecal

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2
Q

The Ileo-caecal valve acts as as one way valve. Why is this important? (3)

A
  • Allows digested contents of small intestine to enter caecum
  • Prevents colonic bacteria proliferating into ileum
  • Produces urge to defacate
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3
Q

What are the major functions of the large intestine? (5)

A
  1. Absorption of H20 and salt
  2. Secretion of K, HC03, mucus
  3. Absorbs short chain fatty acids
  4. Reservoir
  5. Periodic elimination of faeces
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4
Q

Large intestine motility can be summarised as mass movements, haustration and defecation reflex. Describe these

A

Mass movements- Strong peristaltic contractions of circular muscles in large parts of the colon. Triggered by a meal- Gastrocolic reflex.

Haustration- Non propulsive segmentation caused by contraction of circular muscle.

Defecation reflex- Spinal reflex triggered by distension of the rectum.

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5
Q

The Defecation reflex can be triggered by the afferents and the autonomic nervous system. T/F?

A

True

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6
Q

Summarise the steps involved in the autonomic control of the defecation reflex.

A
  1. Mass movement- Rectum fills with faecal matter
  2. Rectal stretch receptors activated
  3. Activations of afferents to spinal cords
  4. Activation of parasympathetic efferents
  5. Contraction of smooth muscle of rectum and colon- internal anal sphincter relaxes
    • Relaxation of external anal sphincter: Defaecation
      - Contraction of external anal sphincter: Defaecation delayed.
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7
Q

Summarise the afferent section of the defaecation reflex.

A
  1. Mass movement- Rectum fills with faecal matter
  2. Activation of rectal stretch receptors
  3. Activation of afferents to brain- urge to defaecate
  4. Altered firing in efferents to spinal cord
    • Relaxation of external anal sphincter: Defaecation assisted by abdominal contraction
      - Contraction of external anal sphincter: Defaecation delayed.
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8
Q

What are the functions of the colonic flora of bacteria?

A
  1. Increase intestinal immunity
  2. Promote motility and helps maintain mucosal integrity
  3. Secrete vitamin K2, and free fatty acids
  4. Activate some drugs- used in IBD
  5. Role in enterohepatic cycling of compounds.
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9
Q

IBD includes _ and _

A

Ulcerative colitis and Crohns

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10
Q

Summarise the 4 pharmacological agents used in IBD?

A
  1. Aminosalicylates
  2. Glucocorticoids
  3. Immunosuppressants
  4. Biological agents

Effective management also needs

  • Drug therapy
  • Nutrional help
  • Surger- in severe disease
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11
Q

What are the use of Aminosalicylates? What diease is it most useful for.

A

Long term maintenance of remission

Ulcerative colitis

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12
Q

Give an example of Aminosalicylate.

A

Sulfasalazine- Azo bond cam link 5-aminosalicylic acid to sulfapyridine.

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13
Q

Action mechanism of Aminosalicylates like Sulfasalazine?

A

5-Asa (5-aminosalicylic acid) reduces inflammation by inhibiting COX & LOX.

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14
Q

What are some adverse sude effects of aminosalicylates?

A

Rashes, arthralgias blood dyscrasia (bad mixture)

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15
Q

Mesalazine is newer drug that is better tolerated than Sulfasalazine. T/F?

A

True

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16
Q

Glucocorticoids are potent in both colitis and Crohn’s. T/F?

A

True

17
Q

Examples of steroids?

A
  1. Prednisolone
  2. Budesonide
18
Q

Two major side effects of Steroids?

A
  1. Steroid dependency
  2. Steroid resistance
19
Q

When are immunosuppresants used in IBD?

A

When the IBD is unresponsive to steroids. Also known as steroid sparing drug.

Immunosuppresants has a slow onset of action- 6-12 weeks

20
Q

What are the 4 most common immunosuppressants in IBD?

A
  1. Azathioprine- most common, can be used long term.
  2. Ciclosporin
  3. 6-Mercaptopurine
  4. Methotrexate- once weekly dose.
21
Q

What are the biological agents used in IBD? (Mab’s)

A

Mabs- Monoclonal antibodies. V expensive

Given in severe IBD. Hypersensitivity reactions are common

  1. Infliximab
  2. Adalimumab
  3. Vedolizumab
  4. Golimumab
22
Q

Main actions of Mabs?

A

Blocks inflammatory mediator TNFa

23
Q

Irritable bowel syndrome is a long term condition causing inflammation. T/F?

A

False

24
Q

IBS treatment is based on Symptomatic control and improving quality of life

A
25
Q

Two main symptoms of IBS?

A
  1. Diarrhoea
  2. Constipation
26
Q

Main drugs used in IBS?

A
  1. Antispasmodic
  2. Laxative
  3. Antimotility
27
Q

Antispasmodic drugs can be of what two types?

A
  1. Anti-Muscarininc- propantheline bromide
  2. Direct smooth musce relaxants- alverine, pepprmint oil
28
Q

What are the drug types used in Visceral Hypersensitivity?

A
  1. Tricyclic anti-depressants- Amitriptyline, low doses used in IBS to reduce pain perception. Not 1st line, used if antispasmodics not working
  2. Selective Serotonin reuptake inhibitor (SSRI)- Citalopram

GI- Week 4 & 5 (15 decks)

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