Sleep for Health, Well-being & Recovery

A collection of vocabulary terms based on the lecture notes regarding the biological importance, anatomy, and hygiene of sleep for health and recovery.

Sleep

A vital, active state of rest characterized by altered consciousness, reduced sensory activity, and inhibited muscle movement, typically organized into cycles of non-REM and REM sleep lasting $90$–$120\,minutes$.

Endocrine System

A network of glands that produce and release hormones to regulate bodily functions, including metabolism, growth, tissue function, and mood, while maintaining homeostasis.

Glymphatic System

A network that drains metabolic waste, such as amyloid-beta, from the brain by circulating cerebrospinal fluid; its clearance rates are $10\,times$ higher during sleep.

Hypothalamus

A brain region sitting on top of the brain stem containing groups of nerve cells that control sleep and wakefulness; it also controls the pituitary gland.

Suprachiasmatic Nucleus (SCN)

Thousands of cells within the hypothalamus that receive information about light exposure from the eyes to control behavioral rhythms.

Brainstem

Anatomy consisting of the pons, medulla, and midbrain that specifically controls the transitions between wakefulness and sleep.

GABA

A brain chemical produced by sleep-promoting cells in the hypothalamus and brainstem that reduces activity in those specific regions.

Thalamus

A brain structure that sends and receives sensory information to the cerebral cortex; it is quiet during most sleep stages but active during REM sleep, providing images and sounds for dreams.

Pineal Gland

A gland that receives signals from the SCN and increases production of melatonin once lights go down to help induce sleep.

Melatonin

A hormone that regulates the sleep-wake cycle and acts as a powerful antioxidant; its production is suppressed by screen time and bright lights.

Circadian Rhythm

The body's natural $24$-hour clock that regulates sleep-wake cycles and matches them to the external cycle of light and darkness.

Adenosine

A chemical released from cells in the basal forebrain that promotes sleepiness; its actions are blocked by caffeine.

Basal Forebrain

A region near the front and bottom of the brain that promotes both sleep and wakefulness through the release of adenosine.

Amygdala

An almond-shaped structure involved in processing emotions that becomes increasingly active during REM sleep.

Human Growth Hormone (HGH)

An anabolic hormone essential for tissue repair and muscle growth, the majority of which is released during deep (slow-wave) sleep.

Cortisol

The stress hormone that reaches its lowest levels at night; sleep inhibits the HPA axis to allow the body to recover from daytime stress.

Leptin

An appetite hormone that signals fullness; proper sleep keeps these levels high to prevent metabolic disruption.

Ghrelin

An appetite hormone that stimulates hunger; sleep deprivation causes these levels to elevate, leading to increased hunger.

Insulin Sensitivity

The body's efficiency in managing blood sugar; proper sleep enhances this, reducing the risk of insulin resistance and supporting pancreatic health.

Sleep Hygiene

Practices such as maintaining a pitch-black room, having a consistent bedtime routine, and avoiding screens to optimize the quality of rest.

Metabolic Overload

A state occurring when muscles exercise to the point of fatigue, exhausting glycogen; the body replenishes this glycogen during sleep.

Biphasic Sleep

A natural, historical tendency toward having two distinct sleep periods, which supports the acceptance of napping as a method for being well-rested.

Polysomnography

An objective method of assessing sleep, alongside tools like actigraphy and sleep diaries, used to diagnose disorders like insomnia.

HPA Axis

The hypothalamic-pituitary-adrenal axis, which regulates stress; its activity is inhibited by sleep to facilitate recovery.

Amyloid-beta

A metabolic waste product in the brain that is cleared by the glymphatic system during sleep.