Narcolepsy and orexin
A young adult falls asleep suddenly during the day, enters REM within minutes of falling asleep, and collapses briefly when laughing. Loss of which neurons is most likely responsible?
Answer D: explanation for every choice
A
Substantia nigra dopamine loss causes Parkinson's disease.
B
Loss of nucleus basalis cholinergic neurons is associated with Alzheimer's disease.
C
Raphe serotonin neurons are not the primary cause of narcolepsy.
D
Correct. Narcolepsy with cataplexy results from loss of orexin neurons, which stabilize wakefulness. Cataplexy is REM muscle atonia intruding into waking.
TakeawayNarcolepsy: orexin loss lets REM intrude into wakefulness.
See your set score →
Reviewed 2026-11-05 by a medical student. Spot an error? Report it with question ID ps163.