Physiology of Nausea and Vomiting Flashcards
what is nausea
subjective, highly unpleasant ‘sinking’ sensation
felt in throat and stomach
describe retching
dry - no efflux of vomitus
describe vomiting
forceful expulsion of gastric/intestinal contents out of the mouth
events in vomiting
Commences with forceful inspiration, reflex closure of the glottis and elevation of the soft palate to close off the airways and nasal passages
stomach, oesophagus and associated sphincters are relaxed
major consequences of severe vomiting
dehydration loss of gastric protons and chloride hypokalaemia loss of duodenal bicarbonate (rare) oesophageal damage (rare)
chemoreceptor trigger zone (CTZ)
vagal afferents to VC stimulated by;
mechanical stimuli
pathology
toxic materials and drugs in the blood
nucleus tractus solitarius (NTS)
vagal afferents to VC stimulated by;
mechanical stimuli
pathology
what is the vomiting centre (VC)
group of interconnected neurones to co-ordinate vomiting
where is motor output that co-ordinates vomiting located
brain stem
clinical features of vomiting
preceded by; profuse salvation sweating elevated heart rate sensation of nausea
clinical features of vomiting
preceded by; profuse salvation sweating elevated heart rate sensation of nausea
where is CTZ located
brainstem - lacks blood brain barrier
where is NTS located
brainstem
what drives the VC
central pattern generator (CPG) (which receives from NTS)
consequences of loss of gastric protons and chloride
hypocholaemic metabolic alkalosis - raising of blood pH
