A defect in activity of which of the following hormones has been associated with the sleep disorder known as narcolepsy?
A) agouti-related peptide, AgRP
B) cocaine- and amphetamine-regulated transcript, CART
C) galanin-like peptide, GALP
D) melanin-concentrating hormone, MCH
E) orexin A

Question

Quizplus · Accepted Answer

Orexin A is a hormone that plays a crucial role in regulating wakefulness and arousal. A deficiency in orexin (also known as hypocretin) is associated with narcolepsy, a sleep disorder characterized by excessive daytime sleepiness and sudden loss of muscle tone (cataplexy).  The orexin peptides function to increase food consumption. However, in addition to increased feeding behavior central orexin action increases wakefulness and suppresses REM sleep. These latter observations demonstrate that orexins play a causative role in the regulation of sleep-wake cycles. Indeed, loss of orexin function results in a condition in animals that mimics the sleep disorder in humans known as narcolepsy.

A Defect in Activity of Which of the Following Hormones