L15- Nausea And Vomiting Flashcards
Vomiting/remiss definition
Forceful expulsion of gastric contents controlled by the vomiting centre.
It’s a physiological response to remove toxic substances
How does vomiting centre cause vomiting
It causes:
Closure of glottis
Lower oesophageal sphincter relaxation
Stops respiration
Increases abdominal pressure
This leads to contraction of abdominal muscles/antiperistalsis/squeeze
Physiological causes of vomiting
Ingestion of toxic substances
Vestibular system- motion sickness
Cranial nerve- irritation of pharynx
Vagal and ens- irritation of GIT
Where’s vomiting centre located
medulla
What is the trigger zone
Input from area postrema/ chemoreceptor trigger zone
What regions of the brain aren’t protected by BBB
Subfornicalborgan- circulating levels of angiotensin 2
Pineal gland- circadian rhythm
OVLT - temp control/fever induction
posterior pituitary- oxytocin and vasopressin levels
Median eminence- neurohormonal control of autonomic system
Area postrema - circulating toxins, controls vomiting reflexes
Usefulness of emetics
Only useful in emergency situations after ingestion of toxin
Receptor systems underlying Emesis
CTZ- d2& 5HT receptors
Vomiting centre- mACh& 5HT receptors
Vestibular nuclei- mACh and H1 receptors
Visceral adherents - 5HT receptors
Cerebral cortex- GABA
Targeting these receptors reduces emesis
Modulators of these pathways are anti-emetics
CTZ
Chemoreceptor trigger zone
Clinical uses of anti-emetics
Morning sickness
Motion sickness
Chemo drugs
Radio therapy
Cinnarizine targets
Antihistamine
Promethazine targets
Antihistamine
Weak mACh antagonist
Hyoscine
MACh antagonist
ondesterone
5HT antagonist (used in cancer treatment)
Hyperemesis gradium
Excessive nausea and vomiting during pregnancy - treated with antiemetics,vitamins steroids and iv fluids
