Symptoms Of GI Disease: Nausea, Vomiting And Pain Flashcards
What is the main aim of nausea and vomiting?
Poison defence system
What physiological changes are associated with nausea?
Shaky, pale and clammy, decreased gut motility and hormone changes
What does nausea trigger?
An aversion to a thing
What is an aversion?
Strong dislike or disinclination which leads to behavioural changes
What is the difference between vomiting and nausea?
Nausea is a sensation and vomiting is a physical act
What is the scientific name for vomiting?
Emesis
What happens in emesis?
Contents of upper GI tract expelled via mouth
What is the relationship between nausea and vomiting?
Produced by the same stimulus
Nausea generally preempts vomiting but one may happen without the other
What are the 13 emetic stimuli?
Poisining, GI infection, excessive alcohol, pregnancy, excessive eating, travel sickness, emotional upset, obstruction, raised intracranial pressure, metabolic disturbance, GI disease, IV drugs and other people being sick
How does taste and smell protect against ingested toxins?
- prevent ingestion
- built in dislike of bitter flavours
- children don’t like trying new stuff
What are the gastric and upper GI protection against ingested toxins?
- expel harmful agents before they can be absorbed
- associated with chemoreceptors cells
What do the gastric chemoreceptive cells respond to?
Naturally occurring toxins, damaging chemicals and inflammatory mediators
What is the chemoreceptor trigger zone?
The area postrema in the brainstem is where the blood-brain barrier is leaky and chemoreceptors can detect toxins in the blood
What is the vestibular system?
Organ of balance but also a strong trigger for emesis
Where is the nucleus tractus solitarius found?
In the medulla of the brainstem
What does the nucleus tractus solitarius do?
Integrates cardiac, respiratory and GI functions
What are the four types of warning inputs in the nucleus tractus solitarius?
- Visceral afferents in the stomach and duodenum
- area postrema
- vestibular system
- higher centres
What happens to the area postrema if there is a raise in intercranial pressure?
Gets squeezed out of the bottom of the skull, causing vomiting
What are the four types of visceral afferents in the stomach and duodenum?
Toxins, irritants, inflammation and distension
What nerve are the vestibular systems signals sent through?
8th cranial nerve
What are the three places the NTS can stimulate?
Higher centres, hypothalamus and autonomic efferents
What are the higher centres the NTS stimulates and what does it cause?
Cerebral cortex/ limbic system -> nausea and future avoidance
What does the NTS cause the hypothalamus to secrete?
ADH
What does the NTS cause autonomic efferents to do?
Increase salivation and vasoconstriction in the GIT
Why does the NTS make the body increase salivation?
More protection against acidic chyme as saliva is alkaline
Why does the NTS cause vasoconstriction in GIT?
Reduce absorption of substance into bloodstream
What are the 5 steps the NTS takes to trigger nausea and vomiting?
- reduces mixing and peristalsis
- proximal stomach relaxes
- giant retrograde contraction
- retching
- vomiting
Why does the NTS reduce mixing and peristalsis?
Prevents toxins being carried through the system
Why does the NTS relax the proximal stomach?
Means stomach is prepared to receive additional contents
Why does the NTS cause a giant retrograde contraction?
Takes contents from mid-small intestine into the stomach
What is the giant retrograde contraction controlled by?
Efferent vagal nerves
What is retching?
Coordinated contractions of abdominal muscles and diaphragm
Why is there no expulsion in retching?
Anti-reflux barriers intact
What happens in the abdomen during retching?
Waves of high pressure- compresses stomach
What happens when you vomit?
Oesophageal sphincters and crural diaphragm relaxes and further waves of contraction
How are pain signals carried to the brain?
Visceral afferent nerves that converge on the greater and lesser splanchnic nerves at the thoracic vertebral level
What do ‘pain’ receptors respond to?
Noxious stimuli
What are ‘pain’ receptors actually called?
Nociceptors
What do nociceptors respond to?
Distension, inflammation and muscle spasm
What are noxious stimuli?
Things that have, are, or will cause damage to the body
What inflammatory mediators do nociceptors respond to?
Injury, irritants, toxins, infection and autoimmunity
What does inflammation do to nociceptors?
Depolarises them
What do nociceptors do when depolarised?
Release proinflammatory chemicals
What happens when positive nociceptor feedback increases?
Synapse potentiation
What can the positive feedback synapse potentiation lead to?
Potentially self-sustaining activity that persists beyond the original cause
How is somatic pain precisely localised?
Impulse taken to the somatosensory cortex, where there’s a map of the of the body
What’s the map of the body in the somatosensory cortex called?
Somatosensory homonculus
What is viscerosomatic convergence?
When an impulse synapses with a somatic nociceptor nerve at the spinal cord
What does viscerosomatic convergence cause?
Referred pain
What do the afferent nerve synapse segments match?
The embryonic origin of each organ
Why can gallbladder infections refer their pain to C3-5?
Infection spreads to parietal peritoneum and diaphragm, and C3-5 is where their nerves come from
What are the characteristics of visceral pain?
- referred to regions of the body wall
- diffuse and poorly located
- each organ has characteristic patterns of referral
Why is visceral pain generally referred to regions of the body wall?
Viscerosomatic convergence
Why is visceral pain diffuse and poorly localised?
There’s a relatively small number of afferents and imprecise wiring
