Disruption of circadian rhythms due to crossing time zones is known as which condition?

• A. Narcolepsy
• B. NREM sleep
• C. Jet lag
• D. Hypnagogic sensations

Answer: (C)

Jet lag happens when your internal circadian rhythm is out of step with the local time after crossing time zones. Your brain’s clock is reset by light cues, but rapid travel can leave it aligned to your origin while the outside world follows a new schedule, producing daytime sleepiness, insomnia at night, fatigue, and grogginess. The body gradually realigns with the new light-dark cycle, and travel direction matters—eastward trips, which require the clock to advance, are usually harder than westward ones. Other options describe different phenomena: narcolepsy is a disorder of sudden sleep attacks, NREM sleep is a sleep stage, and hypnagogic sensations are dreamlike experiences at sleep onset.