Symptoms of GI disease Flashcards
What is the difference between nausea and vomiting?
Personal, self reported Associated with physiological changes Unpleasant Triggers aversion Aversion- a strong dislike or disinclination Vomiting (emesis) is a physical act: Expels contents of upper GI tract via mouth Forceful (cf regurgitation, reflux) Complex, co-ordinated reflexive events Associated with sensation of relief
What is the difference between nausea and vomiting?
Personal, self reported Associated with physiological changes Unpleasant Triggers aversion Aversion- a strong dislike or disinclination Vomiting (emesis) is a physical act: Expels contents of upper GI tract via mouth Forceful (cf regurgitation, reflux) Complex, co-ordinated reflexive events Associated with sensation of relief
What causes nausea and vomiting?
GI infection (e.g. norovirus) Excessive alcohol Pregnancy Excessive eating Travel sickness Metabolic disturbance Other people being sick i.v. drugs (e.g. morphine, chemotherapy) Raised intracranial pressure GI disease (e.g. gastritis) Obstruction Emotional upset Poisoning (e.g. contaminated food, poisonous plants, chemical agents) Kirusikan in a nurse's outfit
How do gastric and upper GI afferents influence nausea and vomiting?
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- e.g. chemotherapy, systemic infection, metabolic disturbance
Chemoreceptor trigger zone:
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- e.g. chemotherapy, systemic infection, metabolic disturbance
Vestibular system:
The organ of balance, but also a potent trigger for emesis
Poisoning is thought to produce aberrant activity in vestibular neural pathways
BUT also triggers N & V in response to un-natural motion
Protection against ingested toxins
Prevention of ingestion- learning and aversion:
If we survive a mistake we avoid repeating it (unpleasantness reinforces learning)
Aversion may hard-wire avoidance
BUT can create incorrect association
What are the mechanisms of nausea and vomiting?
Our anti-poison defences are co-ordinated by the nucleus tractus solitarius (NTS)
Found in the medulla of the brainstem
It also integrates cardiac, respiratory and gastrointestinal functions
It receives four different types of “warning” inputs
What are the visceral afferents?
The afferents are the sensory nerves that run up into the brainstem
They get their input from chemoreceptor cells that are found in the wall of the stomach and the duodenum
These chemoreceptor cells are responsive to toxins, irritants, inflammation and (some abnormal distension)
What is the area postrema?
Aka chemoreceptive tigger zone (CTZ)
It is found in the brain stem very close to the NTS
There is no blood brain barrier, so brain cells here can respond to toxins in the blood
If you have raised intercranial pressure the brain swells and the extra volume tends to gets squeezed out of the foramen magnum with the area postrema and NTS getting pushed
What is the vestibular system?
Organ of balance, inner ear
Its sends its axons through the with cranial nerve to the NTS
How do higher centres influence vomiting and/or nausea?
Things that your social groups find disgusting
Other people in your group being sick
Things that made you sick in the past
How does the NTS trigger nausea and vomiting?
Inputs from the higher centres produces nausea
NTS projecting to the hypothalamus increases ADH hormone to save water (if you’re going to vomit you will lose a lot of fluid)
NTS to autonomic efferent which increases salivation, to give a good fluid lining to the mucosa, and vasoconstriction of the GIT to reduce the absorbance of substances into the bloodstream
The autonomic efferents also changes the gut motility so peristalsis won’t carry that food further down to be absorbed
What are the steps that are taken for the NTS to trigger nausea and vomiting?
- Reduced mixing and peristalsis- prevents toxins from being carried further through the system (vagus nerve)
- Proximal stomach relaxes- prepares stomach to receive additional contents (vagus nerve)
- Giant retrograde- sweeps up from mid-small intestine, returns upper intestinal contents to stomach (vagus nerve)
- Retching (dry heaves):
Co-ordinated contractions of abdominal muscles and diaphragm
Waves of high pressure in abdomen (phrenic nerve)
Compresses stomach but anti-reflux barriers intact so no expulsion - Vomiting (emesis)
Oesophageal sphincter and crural diaphragm relax
Further waves of contraction expel stomach contents (Somatic nerves)
What causes nausea and vomiting?
GI infection (e.g. norovirus) Excessive alcohol Pregnancy Excessive eating Travel sickness Metabolic disturbance Other people being sick i.v. drugs (e.g. morphine, chemotherapy) Raised intracranial pressure GI disease (e.g. gastritis) Obstruction Emotional upset Poisoning (e.g. contaminated food, poisonous plants, chemical agents) Kirusikan in a nurse's outfit
How do gastric and upper GI afferents influence nausea and vomiting?
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- e.g. chemotherapy, systemic infection, metabolic disturbance
Chemoreceptor trigger zone:
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- e.g. chemotherapy, systemic infection, metabolic disturbance
Vestibular system:
The organ of balance, but also a potent trigger for emesis
Poisoning is thought to produce aberrant activity in vestibular neural pathways
BUT also triggers N & V in response to un-natural motion
Protection against ingested toxins
Prevention of ingestion- learning and aversion:
If we survive a mistake we avoid repeating it (unpleasantness reinforces learning)
Aversion may hard-wire avoidance
BUT can create incorrect association
What are the mechanisms of nausea and vomiting?
Our anti-poison defences are co-ordinated by the nucleus tractus solitarius (NTS)
Found in the medulla of the brainstem
It also integrates cardiac, respiratory and gastrointestinal functions
It receives four different types of “warning” inputs
What are the visceral afferents?
The afferents are the sensory nerves that run up into the brainstem
They get their input from chemoreceptor cells that are found in the wall of the stomach and the duodenum
These chemoreceptor cells are responsive to toxins, irritants, inflammation and (some abnormal distension)
