Circadian Dysfunction

Question 1

What is jet lag?

Answer 1

• Transientdisorder associated with excessive daytime sleepiness, sleep onset insomnia, and frequent arousals from sleep

• SCN resets to local time in ~1 day based on light signals, but peripheral oscillators can take more than a week to adjust

Question 2

Explain jet lag after a sleep phase advance

Answer 2

Phase Advance: Going to bed earlier than the circadian bedtime (i.e., before production of melatonin)

Phase Delay: Going to bed later than the circadian bedtime (i.e., after production of melatonin)

• The body’s free-running rhythm is slightly longer (i.e., 24.5 hours) than the 24-hour day.
• We can tolerate a phase delay better than a phase advance.

Question 3

Describe Sleep wake disorders in blind individuals

Answer 3

• Continual circadian desynchrony through a failure of light information to reach the SCN, resulting in cyclical episodes of poor sleep and daytime dysfunction.
• Daily melatonin administration, which provides a replacement synchronizing daily “time cue,” is a promising therapeutic strategy.
• Social rhythm therapy to set peripheral clocks.
• It is possible that blue-light sensitive retinal ganglion cells are functional in some visually impaired individuals

Question 4

Describe social jet lag

Answer 4

Chronobiology:individual“chronotype” (i.e., larks versus owls)
➢ Adolescents tend to be more “owl-like”
➢ Individual differences may have a genetic component
• Familial Advanced Sleep Phase Syndrome & PER2
gene
• 24-hr golden hamsters vs. 20-hr mutant tau hamsters

• Nightshiftworkisassociatedwith:
➢Psychiatric disorders
➢ GI disorders
➢ High blood pressure