Week 6 GI Flashcards
Emesis is controlled by the vomiting centre, also known as the:
Central Pattern Generator (CPG)
Where is the Chemo Receptor Trigger Zone located? (CTZ)
Dorsal surface of the medulla oblongata
Where does the CTZ (chemo receptor trigger zone) receive input from?
Blood bound drugs and hormones
What causes blood bound drugs and hormones to stimulate the CTZ (chemoreceptor trigger zone)? (4)
Drugs
Toxins
Chemo
Hypoxia
What is the medulla oblongata?
Continuation of the spinal cord into the skull
Lowest part of the brain stem
Contains control centres for heart, lungs and CTZ
What are of the brain is responsible for motion sickness?
Vestibular apparatus
What area of the brain is responsible for vomiting r/t psychiatric disorders, stress, anxiety, anticipation?
Cerebral Cortex
What stimulates the visceral afferent nerves in the GI tract to send signals to the vomiting centre? (3)
Distention
Chemo
Radiation
- in the medulla oblongata of the brainstem
- has permeable capillaries and sensory neurons
- detects circulating chemical messengers in blood and transduces them into neural signals and networks
- sensory transducer = integrates blood-to-brain autonomic functions
- detection of circulating hormones involved in vomiting, thirst, hunger, and blood pressure control
Neurotransmitters responsible for N and V are located in? 3()
- The vomiting centre
- CTZ
- GI tract
The CTZ is composed of?
AP (area postrema)
NTS (nulceus tractus soliatarius)
What to do 1st to tx Nausea and Vomiting? (4)
1-identify CAUSE
2-identify PATHWAY
3- what neurotransmitter involved? what will act on this?
4- what worked in the past?
Muscarinic receptors
acetylcholine activates muscarinic receptors, allowing for a parasympathetic reaction in any organs and tissues where the receptor is expressed (parasympathetic, except for sweat glands= sympathetic)
extrapyramidal sx
Dystonia (continuous spasms, muscle contractions)
Akinesia (motor restlessness)
Parkinsonian sx (rigidity, bradykinesia)
Tremor, tardive dyskinesia
Drug that can induce heart arrhythmias and cardiac arrest (esp in pt over 60 or dose > 30mg od)
Domperidone
Which antiemetic drugs have significant anticholinergic effects?
Prochlorperazine
Promethazine
Drug for motion sickness that causes significant dry mouth?
Scopolamine
What drug should be given pre- nausea?
Ondansetron
(serotonin 5- HT3 antagonists)
** take too long to work
Individual factors affecting emetogenic potential of chemo drugs:
- Hx of motion sickness
- > 50 years old
- Female
- Anxiety
- Absence of heavy alcohol use
- Poor performance status
Things that can effect emetogenic potential:
- Infusion time (longer time= less nausea)
- Dose (higher dose= worse)
- Number of drugs