Anatomy & Physiology
Infants spend 50% of their sleep in this stage to support rapid brain maturation, whereas adults only spend 20-25% of the night in it.
What is REM sleep?
This source of natural light is the strongest daily signal for setting your circadian rhythm.
What is sunlight?
This metabolic condition becomes more likely with chronic sleep deprivation due to impaired glucose tolerance and insulin resistance.
Using your phone in bed is an example of poor __________.
Avoiding this stimulant in the afternoon helps prevent difficulty falling asleep at night.
What is caffeine?
This stage of sleep progressively decreases with age and contributes to lighter, more fragmented sleep in older adults.
This daytime activity can help you fall asleep more easily and deepen your sleep at night.
Impaired endothelial function, increased sympathetic tone, and elevated inflammatory markers are key mechanisms linking chronic sleep restriction to this major class of disease.
What are cardiovascular diseases?
This sleep hygiene behavior means using your bed only for sleep—not for homework, watching TV, or scrolling.
What is reserving the bed for sleep only?
This healthy habit stabilizes your circadian rhythm by keeping your bedtime and wake time the same every day.
What is maintaining a consistent sleep schedule?
This waste clearing system becomes active primarily during deep sleep to flush neurotoxins (e.g. beta-amyloid) out of the brain.
What is the glymphatic system?
Exposure to bright light during this time of the day will cause a phase advance of the circadian rhythm, leading to earlier sleep onset and wake times.
What is early morning?
This neurotransmitter, elevated at night in insomnia, contributes to heightened autonomic arousal.
What is norepinephrine?
This nighttime routine involves dimming lights, reducing screens, and calming activities.
What is a bedtime wind-down routine?
Optimal sleep timing typically results in a sleep midpoint between these two hours.
What is 1-3pm?
Before the industrial revolution and lightbulb, humans typically slept in two distinct segments separated by a waking period known as “the watch.”
What is biphasic sleep?
This type of noise—from traffic, neighbors, or sirens—can cause micro-awakenings and reduce sleep quality.
What is environmental noise?
This anabolic hormone decreases with sleep deprivation and contributes to impaired muscle recovery.
What is growth hormone (or testosterone)?
This common nighttime noise can disrupt sleep and may signal a breathing disorder.
What is snoring?
Naps longer than this threshold may correlate with poorer cognitive outcomes in urban populations.
What is 90 mins?
A hypothalamic nucleus that promotes sleep by inhibiting ascending arousal systems using GABA and galanin, functioning as part of a flip-flop switch.
What is the ventrolateral preoptic nucleus (VLPO)?
Shift workers are advised to avoid strong morning light exposure after night shifts because of its powerful effect on this brain structure, the master pacemaker of circadian timing (nucleus).
What is suprachiasmatic nucleus (SCN)?
This core mechanism underlies poor sleep, involving persistent activation of autonomic, neuroendocrine, and CNS arousal systems.
What is hyperarousal?
A patient experiencing conditioned arousal—such as racing thoughts or anxiety triggered simply by getting into bed—meets clinical criteria suggesting benefit from this specific behavioral therapy.
What is CBT-I?
Wearing sunglasses on the commute home, maintaining a consistent sleep schedule, and using blackout curtains are strategies for shift workers trying to protect this internal timing system.
What is circadian rhythm?