21 Anti-emetics, Anti-diarrhoeals and Laxatives

Question 1

What is the difference between vomiting and regurgitation?

Answer 1

Vomiting= Involuntary, forceful expulsion of gastric contents

Regurgitation= effortless expulsion- contents might be in oesophagus

Question 2

How does vomiting occur?

Answer 2

Vomiting centre in medulla signals to vomit

1. Nausea, salivation, sweating
2. Retrograde peristalsis
3. Deep inspiration
4. Closure of glottis (choking if not closed- eg if drugged)
5. Adbominal muscles contract
6. Lower oesophageal spincter relaxes

Question 3

Where is the chemoreceptor trigger zone (CTZ)? What are the 4 triggers?

Answer 3

CTZ= area of medulla- area postrema- floor of 4th ventricle- on blood side of blood brain barrier

1. Sensory afferents via midbrain (eg seeing something gross)
2. Vestibular nuclei (motion sickness)
3. Visceral afferents from gut - via vagus nerve
   
   1. eg problem in gut- sends signals to CTZ
4. Direct triggers (eg chemotherapy/hormones)