Symptoms of GI disease: nausea , pain and vomiting Flashcards
1
Q
what is nausea ?
A
- a sensation
- personal, self reported
- associated with physiological changes
- unpleasant
- triggers aversion
2
Q
what is vomiting (emesis) ?
A
- usually follows nausea
- physical act
- expels contents of upper GI tract via mouth
- forceful (cf regurgitation, reflux)
- complex, co-ordinated reflexive events
- associated with sensation of relief
3
Q
what is the relationship between nausea and vomiting ?
A
- Nausea is produced by the same stimuli as vomiting
- Nausea is generally a prodrome (ie premonitory symptom) of vomiting
- Nausea may clear up without triggering vomiting
- AND vomiting can occur without prior nausea
4
Q
what are some emetic stimuli ?
A
5
Q
how do taste and smell protect us against ingested toxins ?
A
- can prevent ingestion
- we have a built-in dislike of bitter flavours
- we can taste see and smell when food has gone off
- children are wary of novel flavours
- we learn from our elders what is safe
6
Q
how do gastric and upper GI afferents protect us against ingested toxins ?
A
- can potentially expel harmful agents before they have (much) chance to be absorbed
- associated with chemoreceptive cells that respond to:
- naturally occurring toxins
- damaging chemicals
- inflammatory mediators
- BUT non-ingested toxins will have the same effect – eg chemotherapy, systemic infection, metabolic disturbance
7
Q
how does the chemoreceptor trigger zone protect us against ingested toxins ?
A
- the area postrema in the brainstem
- blood-brain barrier is “leaky”
- chemoreceptors that can detect toxins in the blood
- BUT non-ingested toxins will have the same effect – eg chemotherapy, systemic infection, metabolic disturbance
8
Q
how does the vestibular system protect us against ingested toxins ?
A
- the organ of balance, but also a potent trigger for emesis
- poisoning is thought to produce aberrant activity in vestibular neural pathways
9
Q
how does Prevention of ingestion – learning and aversion protect us against ingested toxins ?
A
- if we survive a mistake we avoid repeating it (unpleasantness reinforces learning)
- aversion may hard-wire avoidance
- BUT can create incorrect associations eg eating before chemotherapy
10
Q
what is the NTS ?
A
- nucleus tractus solitarius
- where Our anti-poison defences are co-ordinated
- Found in the medulla of the brainstem
- It also integrates cardiac, respiratory and gastrointestinal functions
- vomiting centre
11
Q
what are the 4 types of warning inputs that the NTS receives ?
A
12
Q
how does the NTS trigger nausea ?
A
13
Q
what happens in the gut to trigger nausea ?
A
14
Q
what are the mechanisms of vomiting ?
A
15
Q
what are nociceptors ?
A
- “Pain” receptors respond to “noxious” stimuli, and are called “nociceptors”
They respond to: - distension
- inflammation
- muscle spasm
they do not respond to pain
16
Q
how do nociceptors respond to excess distention
A
17
Q
how do nociceptors respond to inflammation ?
A
- Inflammation depolarises these nociceptors
- When depolarised they release pro-inflammatory chemicals
- This positive feedback increases responses . . .
. . . . which can in turn potentiate synapses - Leading to potentially self-sustaining activity that persists beyond the original cause
18
Q
how is somatic pain localised ?
A
- Nociceptors Activation: When there’s damage or irritation to tissues (like a cut or muscle strain), nociceptors in those areas are activated by chemical signals (e.g., prostaglandins or bradykinin).
- Afferent Nerve Fibers: The activated nociceptors send pain signals through sensory nerve fibers (A-delta and C fibers) to the spinal cord.
- Spinal Cord Transmission: The signals are transmitted to the brain via the spinal cord, specifically to the somatosensory cortex, a part of the brain that processes touch and pain sensations.
- Localizing Pain: The brain uses the pattern of signals received from specific areas of the body to localize the pain. The more sensory receptors in a particular area, the more accurately the brain can pinpoint the location of the pain.
19
Q
describe viscero-somatic convergence
A
- Viscero-somatic convergence refers to the phenomenon where sensory signals from internal organs (viscera) and from the skin or muscles (somatic tissues) are processed by the same neurons in the spinal cord.
- this can lead to confusion in the brain about the true source of pain, which is why pain from internal organs, like the heart or esophagus, is often felt in other areas of the body, such as the chest or back.
Example: Esophageal Nociceptor
* The esophagus, an internal organ, has nociceptors that respond to injury, irritation, or inflammation (such as from acid reflux). These nociceptors send pain signals to the spinal cord.
- Convergence: The nociceptors from the esophagus send their pain signals to the spinal cord, specifically to the same regions where pain from somatic tissues, like the chest or upper abdomen, is processed. This happens because sensory neurons from both the esophagus and somatic tissues (e.g., skin over the chest) converge on the same spinal cord neurons.
- Referred Pain: Because of this convergence, the brain may misinterpret the source of the pain. For example, pain originating from the esophagus (like in acid reflux or heartburn) may be felt as chest pain or in the upper back, rather than being correctly localized to the esophagus.
20
Q
what are the characteristics of visceral pain ?
A
- Generally “referred” to regions of the body wall
due to viscero-somatic convergence - Often diffuse and poorly localised
relatively small number of afferents
imprecise wiring - Each organ has a characteristic pattern of referral
initially to dermatomes matching the embryonic origin of the organ - but may evolve as other tissues are affected
