A nurse is caring for a patient who has been newly prescribed ondansetron (Zofran) for post-operative nausea. What is the mechanism of action for ondansetron?

Ondansetron agonizes serotonin receptors on afferent vagal neurons.

Ondansetron agonizes serotonin receptors in the medulla oblongata.

Ondansetron agonizes dopaminergic receptors in the vestibular apparatus.

Ondansetron blocks serotonin receptors in the chemoreceptor trigger zone.