Nausea, Vomiting, Pain

Question 1

What’s nausea?

Answer 1

Sensation:

personal, self reported, associated w physiological changes, triggers aversion

Question 2

What’s vomiting (emesis)?

Answer 2

Physical act:

expels contents of upper GI via cf regurgitation+ reflux, coordinated reflexive events,associated w sensation of relief

Question 3

What’s the relationship between nausea + emesis?

Answer 3

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

Question 4

How taste + smell protects against ingested toxins?

Answer 4

built-in dislike of bitter, children wary of novel flavours,

learn from elders what’s safe

Question 5

How gastric+upper GI afferents protects against ingested toxins?

Answer 5

Expel harmful agents before absorbed associated w chemoreceptive cells that respond to: irritants,🐛toxins, inflammatory mediators

Question 6

How Chemoreceptor Trigger Zone protects against ingested toxins?

Answer 6

the area postrema in the brainstem, BBB ‘s “leaky”, chemoreceptors detects toxins in the blood

Question 7

How vestibular system protects against ingested toxins?

Answer 7

organ of balance, potent trigger for emesis poisoning produces aberrant activity in vestibular neural pathways

Question 8

☹ of vestibular system?

Answer 8

vestibular malfunction triggers N+V

Question 9

☹ of gastric+upper GI afferents, Chemoreceptor Trigger Zone?

Answer 9

no effect on non-ingested toxins eg chemotherapy, systemic infection, metabolic disturbance

Question 10

How learning + aversion protects against ingested toxins?

Answer 10

after mistake we avoid repeating it ∵unpleasantness reinforces learning
aversion hard-wires avoidance

Question 11

☹ learning + aversion

Answer 11

create incorrect associations

Question 12

What’s anti-poison defense coordinated by?

Answer 12

Nucleus Tractus Solitarius NTS -in the medulla, integrates ❤, respiratory and GI functions

Question 13

What inputs does NTS receive?

Answer 13

addominal afferents
area posterma
vestibular system
higher centres

Question 14

What are abdominal afferents?

Answer 14

involve upper GI tract signals from vagus: toxins, irritants, distention

Question 15

What are the signals from area posterma?

Answer 15

located on 4th base ventricle of the brain-toxins detected here sends signals

Question 16

What are the signals from vestibular system?

Answer 16

vestibular receptors disrupted by toxins∴imbalance in the body sends signals

Question 17

What are the signals from higher centres?

Answer 17

processes world +👁emesis stimuli-visual, emotional,aversive–>anticipatory N+V (eg anticipating chemotherapy)sends signals

Question 18

What 💊 ↓N+V?

Answer 18

5HT3 antagonists ∵ area postrema + abdomen have 5HT3 receptors

Question 19

How’s N caused?

Answer 19

NTS sends signals to:
frontal cortex + some limbic area
hypothalamus
organs via autonomic efferents

Question 20

How’s N sensation caused

Answer 20

NTS sends signals to frontal cortex + some limbic area

Question 21

What happens when NTS sends signals to hypothalamus?

Answer 21

⇶ADH- retain H2O as fluid will be lost while vomiting

Question 22

What happens when NTS sends signals to organs via autonomic efferents?

Answer 22

• ↓gut motility -↓substance passes
• vasoconstriction of gut-↓ toxin absorption
• sweating+salivation

Question 23

Mechanism of N via vagus?

Answer 23

• ↓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

Question 24

Mechanism of V via phrenic + somatic nerves?

Answer 24

• 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

Question 25

Situations where vomiting occurs?

Answer 25

• 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

Question 26

Where are visceral afferents?

Answer 26

Greater splanchnic (sympathetic) nerves  ~T1-9
Lesser splanchnic (sympathetic) nerves  ~T10-12

Question 27

Where’s visceral input?

Answer 27

Nociceptors= respond to ‘noxious’ stimuli eg distension, inflammation,muscle spasm

Question 28

How do nociceptors respond to inflammatory?

Answer 28

responds to inflammatory mediators + stretching of the gut wall

Question 29

What do nociceptors do when depolarised?

Answer 29

⇶ pro-inflammatory chemicals–>+ve feedback loop - contributes to inflammatory bowel disease

Question 30

Why chronic pain w/o main cause?

Answer 30

Abnormal activity potentiates synapses –>↑ nociceptor signals –>self-sustaining

Question 31

Diff between somatic vs visceral pain?

Answer 31

• precisely localised

- referred to body surface, location of pain reported following activation of oesophageal nociceptors imprecise

Question 32

What’s viscero-somatic convergence?

Answer 32

visceral pathways ‘piggy back’ on somatic pathways + 🧠interprets the origin of pain like somatic

Question 33

Dermatomes?

Answer 33

Afferents synapse in segments matches embryonic origin of each organ∴ nociceptor inputs can cause pain at places that are nowhere near the organ

Question 34

Features of visceral pain?

Answer 34

-“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