Symptoms of GI disease Flashcards
What is emesis?
→Expels contents of upper GI tract via mouth
→Forceful (regurgitation, reflux)
→Complex, coordinated reflexive events
→Associated with relief
What is the difference between nausea and vomiting?
→Nausea is produced by the same stimuli as vomiting
→Nausea is generally a prodrome of vomiting
→Nausea may clear up without triggering vomiting
→Vomiting can occur without prior nausea
What causes nausea and vomiting?
→GI infection →Poisoning - contaminated food →Emotional upset →Obstruction →GI disease →Raised intracranial pressure →Metabolic disturbance →Other people being sick →Travel sickness →Excessive eating →Excessive alcohol →Pregnancy →I.V drugs
What are the advantageous causes of vomiting?
→Poisoning
→excessive alcohol
→ excessive eating
→obstruction
What do chemoreceptive cells in the gut respond to?
→Irritants
→Inflammatory mediators
→Bacterial toxins
Why do receptors in the gut wall respond to non ingested toxins?
→Receptors in the gut wall that detect poison have a blood supply
→are in contact with the circulation so they respond to toxins in circulations
→ non ingested toxins will have the same effect e.g chemotherapy, metabolic disturbance or systemic infections.
What is the chemoreceptor trigger zone?
→Area postrema in the brainstem
Why can the area postrema detect toxins in the blood?
→Blood-brain barrier is leaky
→Chemoreceptors can detect toxins in the blood
Describe the set up of the blood brain barrier?
→Within the brain the capillaries have endothelial walls that have tight junction
→ in other places there are big gaps between the endothelial cells so plasma can enter.
→Substances have to be carried across into and out of the brain tissue
→This is a protective mechanism so the brain is not in contact with most things that are transported.
What is the vestibular system?
→The organ of balance but also a potent trigger for emesis
What does poisoning produce in the vestibular system?
→Poisoning is thought to produce aberrant activity in vestibular neural pathways
What are receptors in the vestibular system sensitive to?
→ chemicals
Why can traveling cause nausea?
→Travelling can cause nausea because it produces unnatural patterns of activity in the vestibular system.
What does aversion hardwire?
→Aversion may hardwire avoidance
What are the anti poison defenses coordinated by?
→The anti poison defenses are coordinated by the nucleus tractus solitarius
Where is the NTS found and what does it do?
→Found in the medulla of the brainstem
→Integrates cardiac, respiratory and GI functions
What are visceral afferent receptors associated with?
→ Afferents that run through the parasympathetic nerves through the vagus and into the brainstem.
Where is the area postrema?
→sits below the cerebellum and the foramen magnum ( where the spinal cord is)
What happens if pressure goes up in the skull?
→If pressure goes up in the skull then it presses the brainstem down through the foramen magnum
Why does vomiting occur if pressure goes up in the skull?
→The area postrema is sensitive to the change in pressure so vomiting occurs
What do higher centres in the brain do?
→Things that make you sick in the past
→Other people being sick
How does the NTS cause anti reflux barriers to relax?
→The NTS integrates the information and produces the outputs
→NTS triggers the hypothalamus to increase ADH
→Fluid starts to be conserved
→Sympathetic activity increases
→Reduced parasympathetic activity to upper GI tract
→Pallor and sweating (result of sympathetic activation)
→NTS coordinates muscular activity
→The anti reflux barriers are relaxed
What are the 3 phases of nausea?
→Reduced mixing and peristalsis (reduction of parasympathetic)
→Proximal stomach relaxes (distensible)
→Giant retrograde contraction
Why is there reduced mixing and peristalsis during vomiting?
→Prevents toxins from being carried further through the system
