PHA 3112 Chapter Notes - Chapter 80: Serotonin Antagonist, Muscarinic Antagonist, Chemotherapy-Induced Nausea And Vomiting
10 Dec 2016
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Emesis: complex reflex caused by vomiting centre activation, group of neurons in medulla oblongata in brain stem. Some stimuli activate vomiting centre directly or indirectly. Direct-acting stimuli include: signals from the cerebral cortex (anticipation or fear), signals from sensory organs (upsetting sights, noxious odors, or pain), signals from the vestibular apparatus of the inner ear. 1) indirect-acting stimuli activate chemoreceptor trigger zone (ctz) . 3) vomiting centre signals stomach, diaphragm & abdominal muscles . 1) by signals from stomach & small intestine (traveling via vagus nerve); & 2) by direct emetogenic compound actions (anticancer drugs, opioids, ipecac) carried to ctz in blood. Table 80-2 antiemetic drugs: uses and mechanism of action. Blocks serotonin receptors on vagal afferents and in the ctz. Blocks receptors for substance p/neurokin1 in the brain. Unknown, probably activate cannabinoid receptors associated with vomiting centre. Blocks muscarinic receptors in the pathway from the inner ear to vomiting centre.
