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
Situations where vomiting occurs?
- Poison- remove harmful substances detected by chemoreceptors
- Gastroenteritis (noravirus)- remove viral toxins detected by chemoreceptors
- ⇑🥤- poisonous,detected by chemoreceptors
- 🤰- chemicals + hormones produced stimulates chemoreceptors
- Emotional upset-via higher centers
- ⇑eating-evolutionary so man could re-eat undigested matter
- GI diseases-so food doesn’t go to obstructed area
- ↑ intracranial p-presses on NTS
- 💊-poisonous detected by chemoreceptors
- Metabolic disturbance-others 🤮,precautionary measure preventing poisoning from food being eaten by the group
- ✈🤮-stimulates vestibular system
Where are visceral afferents?
Greater splanchnic (sympathetic) nerves ~T1-9 Lesser splanchnic (sympathetic) nerves ~T10-12
Where’s visceral input?
Nociceptors= respond to ‘noxious’ stimuli eg distension, inflammation,muscle spasm
How do nociceptors respond to inflammatory?
responds to inflammatory mediators + stretching of the gut wall
What do nociceptors do when depolarised?
⇶ pro-inflammatory chemicals–>+ve feedback loop - contributes to inflammatory bowel disease
Why chronic pain w/o main cause?
Abnormal activity potentiates synapses –>↑ nociceptor signals –>self-sustaining
Diff between somatic vs visceral pain?
- precisely localised
- referred to body surface, location of pain reported following activation of oesophageal nociceptors imprecise
What’s viscero-somatic convergence?
visceral pathways ‘piggy back’ on somatic pathways + 🧠interprets the origin of pain like somatic
Dermatomes?
Afferents synapse in segments matches embryonic origin of each organ∴ nociceptor inputs can cause pain at places that are nowhere near the organ
Features of visceral pain?
-“referred” to regions of the body wall ∵ viscero-somatic convergence
-Diffuse+poorly localised ∵ few afferents+imprecise wiring
-Each organ has a characteristic pattern of referral∵
dermatomes matches embryonic origin of the organ but may evolve as other tissues affected
