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GI- WK 1-3 > Physiology & pharmacology of Nausea and Vomiting > Flashcards

Physiology & pharmacology of Nausea and Vomiting Flashcards

1
Q

What is nausea?

A

Unpleasant urge to vomit

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2
Q

Define vomiting.

A

Forceful expulsion of stomach contents via the mouth/nose by contraction of abdominal muscle/diaphragm.

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3
Q

Retching is caused by repetitive _ peristalsis of the stomach and oesophagus without vomiting.

A

Reverse

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4
Q

Regurgitation is a movement of effort of swallowed food contents/acid into the mouth. T/F?

A

False- Effortless movement

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5
Q

What is the main control centre for emesis?

A

Vomiting centre in the medulla

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6
Q

The vomiting centre is stimulated by _ type receptors?

A

Muscarinic

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7
Q

The chemoreceptor trigger zone is found inside the blood brain barrier? T/F?

A

False- outside it, so greater exposure to foreign contents

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8
Q

What type of receptors are found in the chemoreceptor trigger zone? (2)

A
  1. Dopamine 2 (D2) 2. 5-HT
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9
Q

The chemoreceptor can directly stimulate emesis? T/F?

A

False- stimulates vomiting centre–> Vomiting

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10
Q

In what context is the vestibular nuclei important for emesis?

A

Motion sickness

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11
Q

What receptors are found in the vestibular nuclei? (2)

A
  1. Muscarinic 2. Histamine type 1
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12
Q

How does the vestibular nuclei then cause emesis?

A

Vestibular nuclei–> Chemoreceptor trigger zone–> Vomiting centre

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13
Q

Afferent signals from the pharynx and the GI tract can also stimulate the vomiting centre. T/F/

A

True

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14
Q

The higher centres of the brain (cerebral cortex) can also stimulate the vomting centre due to a sight, foul smell etc. T/F?

A

True

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15
Q

What are the pathways (mostly neural) involved in the process of emesis? (5)

A
  1. Toxic material in gut lumen
  2. Enterochromaffin cells in mucosa activated
  3. Depolarisation of sensory afferent terminal in mucosa
  4. AP discharge in vagal afferent to brainstem (CTZ, NTS)
  5. Coordination of vomiting by vomiting centre
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16
Q

The action of vomiting is due to sequential contraction of the stomach, oesophagus and sphincters. T/F?

A

False- relaxation

17
Q

Describe the events of contraction/relaxation leading to emesis.

A
  1. Suspension intestinal slow wave activity
  2. Retrograde contraction from ileum–>stomach
  3. Suspended breathing (closed glottis)- prevents aspiration
  4. Relaxation of LOS- abdominal + diaphragm contraction compresses stomach
  5. Ejection of gastric contents through open UOS.
18
Q

Vagal effernts are sent to which parts the abdomen? (3)

A
  1. Stomach
  2. Oesophagus
  3. Small intestine
19
Q

Somatic motor nerves innervate the _ and _

A

Abdominal muscle & diaphragm

20
Q

Vomiting is usually preceeded by the feeling of _

A

Nausea

21
Q

What are the consequences of severe vomiting?

A
  1. Dehydration
  2. Hypokalaemia
  3. Mallory-weiss tear
  4. Hypocholaraemic metabolic alkalosis
  5. Aspiration- loss of gastric protons/Cl
22
Q

Dopamine antagonists block dopamine receptors found in the _

A

CTZ- chemoreceptor trigger zone

23
Q

Two examples of dopamine antagonists?

A
  1. Prochlorperazine
  2. droperidol
24
Q

What are the actions of pro-kinetic drugs in the

a) Gut
b) CNS

A

Gut- Increase gastric peristalsis & LOS sphincter tone

CNS- Inhibits D2 receptors in CTZ

25
Q

Two examples of pro-kinetic drugs?

A
  1. Metoclopramide
  2. Domperidone
26
Q

5HT3 receptor antagonists block 5-HT receptors found in the _ and _

A

GIT, CNS

27
Q

5HT antagonists are used principally in the management of what type of vomiting?

A
  1. Chemo induced
  2. Radiotherapy induced
  3. Post op induced
28
Q

Two examples of 5HT antagonists? (hint-granny)

A
  1. Granisetron
  2. Ondansetron
29
Q

H1 antihistamines are useful in what situations?

A
  1. Motion sickness
  2. Morning sickness
30
Q

H1 Antihistamines block H1 receptors found where in the brain?

A
  1. VN
  2. NTS
31
Q

Two examples of H1 antihistamines?

A
  1. Promethazine
  2. Cyclazine

H1 antihistamines have an additional Anti muscarinic effect.

Most effective- Take 2 hours before vomiting

32
Q

Anticholinergics block muscarinic receptors found where in the brain?

A
  1. VN
  2. NTS
  3. Vomiting centre
33
Q

Two examples of anticholinergics?

A
  1. Scopolamine
  2. Dicyclomine
34
Q

What are the adjuvant anti-emitics used?

A
  1. NK1 antagonist- aprepitant
  2. Corticosteroids- dexamethazone
  3. Benzodiazepines- diazepam
  4. Cannabinoids- nabilone
35
Q

Chemotherapy induced nausea & vomiting (CINV) requires a triple drug regimen of _ , _ and _

A
  1. 5HT3 antagonist
  2. Aprepitant
  3. Dexamethasone
36
Q

What are the drugs used for post op induced vomiting?

A

•5HT3-receptor antagonists

Droperidol, Prochlorperazine

Cyclizine

Dexamethasone

37
Q

What is hypermesis gravidarum? What is its treatment?

A

Vomiting as a result of electrolyte disturbances, nutritional deficiency etc in pregnancy.

Treatment- H1 antihistamines- cyclizine

38
Q
A

GI- WK 1-3 (25 decks)

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