Nausea, Vomiting, Pain Flashcards
What’s nausea?
Sensation:
personal, self reported, associated w physiological changes, triggers aversion
What’s vomiting (emesis)?
Physical act:
expels contents of upper GI via cf regurgitation+ reflux, coordinated reflexive events,associated w sensation of relief
What’s the relationship between nausea + emesis?
Nausea is produced by the same stimuli as vomiting, generally a prodrome (ie premonitory symptom) of vomiting, can clear up w/o vomiting
Vomiting can occur w/o nausea
How taste + smell protects against ingested toxins?
built-in dislike of bitter, children wary of novel flavours,
learn from elders what’s safe
How gastric+upper GI afferents protects against ingested toxins?
Expel harmful agents before absorbed associated w chemoreceptive cells that respond to: irritants,🐛toxins, inflammatory mediators
How Chemoreceptor Trigger Zone protects against ingested toxins?
the area postrema in the brainstem, BBB ‘s “leaky”, chemoreceptors detects toxins in the blood
How vestibular system protects against ingested toxins?
organ of balance, potent trigger for emesis poisoning produces aberrant activity in vestibular neural pathways
☹ of vestibular system?
vestibular malfunction triggers N+V
☹ of gastric+upper GI afferents, Chemoreceptor Trigger Zone?
no effect on non-ingested toxins eg chemotherapy, systemic infection, metabolic disturbance
How learning + aversion protects against ingested toxins?
after mistake we avoid repeating it ∵unpleasantness reinforces learning
aversion hard-wires avoidance
☹ learning + aversion
create incorrect associations
What’s anti-poison defense coordinated by?
Nucleus Tractus Solitarius NTS -in the medulla, integrates ❤, respiratory and GI functions
What inputs does NTS receive?
addominal afferents
area posterma
vestibular system
higher centres
What are abdominal afferents?
involve upper GI tract signals from vagus: toxins, irritants, distention
What are the signals from area posterma?
located on 4th base ventricle of the brain-toxins detected here sends signals
What are the signals from vestibular system?
vestibular receptors disrupted by toxins∴imbalance in the body sends signals
What are the signals from higher centres?
processes world +👁emesis stimuli-visual, emotional,aversive–>anticipatory N+V (eg anticipating chemotherapy)sends signals
What 💊 ↓N+V?
5HT3 antagonists ∵ area postrema + abdomen have 5HT3 receptors
How’s N caused?
NTS sends signals to:
frontal cortex + some limbic area
hypothalamus
organs via autonomic efferents
How’s N sensation caused
NTS sends signals to frontal cortex + some limbic area
What happens when NTS sends signals to hypothalamus?
⇶ADH- retain H2O as fluid will be lost while vomiting
What happens when NTS sends signals to organs via autonomic efferents?
- ↓gut motility -↓substance passes
- vasoconstriction of gut-↓ toxin absorption
- sweating+salivation
Mechanism of N via vagus?
- ↓Mix+peristalsis prevents toxins carried further
- Proximal stomach relaxes-prepares stomach to receive extra contents
- Giant retrograde contraction-sweeps up from mid-small intestine returning upper intestinal contents to stomach
Mechanism of V via phrenic + somatic nerves?
- Retching/dry heaves-coordinated contractions of abdominal muscles+diaphragm –>🌊of high p in abdomen –> compresses stomach but anti-reflux barriers intact ∴ no expulsion
- Emesis-oesophageal sphincters + crural diaphragm relax, ↑🌊of contraction expels contents
