W9 - Wakefulness and Sleep

Endogenous cycles

Biological rhythms that originate from within the body and continue even without external environmental cues.

Circadian rhythm

A biological rhythm that follows an approximately 24-hour cycle, regulating processes such as sleep and body temperature.

Biological clock

An internal timing mechanism that regulates rhythmic physiological and behavioural processes.

Free running rhythm

A natural biological rhythm that occurs without external time cues and may differ slightly from 24 hours.

Sleep-wake rhythm

The regular pattern of alternating sleep and wakefulness across a 24-hour period.

Negative feedback

A regulatory process in which a change in a system triggers mechanisms that reverse or reduce that change to maintain stability.

Reticular formation

A network of neurons in the brainstem involved in arousal, attention, and the regulation of sleep-wake states.

Electroencephalography

A technique used to measure and record electrical activity in the brain through electrodes placed on the scalp.

Polysomnography

A comprehensive sleep study that records brain activity, eye movements, muscle activity, breathing, and heart rate during sleep.

Paradoxical sleep

Another term for REM sleep, characterised by vivid dreaming and brain activity similar to wakefulness while the body remains largely paralysed.

REM sleep

Rapid eye movement sleep, a sleep stage associated with dreaming, rapid eye movements, and heightened brain activity.

Pons geniculate occipital waves

Bursts of electrical activity that occur during REM sleep and are associated with visual dreaming.

Pontomescencephalon

A region including the pons and midbrain involved in the regulation of REM sleep and arousal.

Locus coeruleus

A nucleus in the brainstem involved in arousal, attention, stress responses, and the release of norepinephrine.

Antihistamines

Medications that block histamine receptors, commonly used to treat allergies and sometimes cause drowsiness.

Histamines

Neurotransmitters involved in wakefulness, arousal, and immune responses.

Orexin

A neurotransmitter produced in the hypothalamus that promotes wakefulness and regulates appetite.

Dorsal Raphe

A group of serotonin-producing neurons in the brainstem involved in mood regulation and sleep.

Basal forebrain

A region of the brain involved in arousal, learning, memory, and the regulation of sleep and wakefulness.

Adenosine

A neurotransmitter that accumulates during wakefulness and promotes sleepiness.

Prostaglandins

Lipid compounds involved in physiological functions including inflammation, fever, and sleep regulation.

Sleep architecture

The structure and pattern of sleep cycles and stages experienced during a night of sleep.

Insomnia

A sleep disorder characterised by difficulty falling asleep, staying asleep, or obtaining restful sleep.

Narcolepsy

A neurological disorder involving excessive daytime sleepiness and sudden episodes of sleep.

Sleep apnea

A sleep disorder in which breathing repeatedly stops and starts during sleep.

Hypnagogic hallucinations

Vivid dream-like sensory experiences that occur while falling asleep.

Sleep paralysis

A temporary inability to move or speak while falling asleep or waking up.

Cataplexy

Sudden loss of muscle tone triggered by strong emotions, commonly associated with narcolepsy.

Night terrors

Episodes of intense fear and partial arousal from deep sleep, usually involving screaming or agitation

Sleepwalking

A disorder involving walking or performing activities while still asleep.

Endogenous circadian rhythms

Internally generated biological rhythms that repeat approximately every 24 hours.

Endogenous circannual rhythm

An internally regulated biological rhythm that occurs on a yearly cycle.

Jet lag

A temporary disruption to circadian rhythms caused by rapid travel across time zones.

Melatonin

A hormone released by the pineal gland that helps regulate sleep and circadian rhythms.

Pineal gland

A small endocrine gland in the brain that secretes melatonin.

Superchiasmatic nucleus

A region of the hypothalamus that acts as the body’s primary circadian clock.

Zeitgeber

An external environmental cue, such as light, that synchronises biological rhythms.

Alpha waves

Brain waves with a frequency of 8–12 Hz associated with relaxed wakefulness.

Brain death

The irreversible loss of all brain function, including brainstem activity.

Coma

A prolonged state of unconsciousness in which a person cannot be awakened and shows little or no response to stimuli.

K-complex

A large brain wave occurring during stage 2 NREM sleep, thought to play a role in memory and sleep protection.

Locus correleus

A misspelling of locus coeruleus, a brainstem nucleus involved in arousal and norepinephrine release.

Minimally conscious state

A condition of severely altered consciousness in which minimal but definite signs of awareness are present.

NREM sleep

Non-rapid eye movement sleep, consisting of stages of sleep ranging from light to deep sleep.

Paradoxical sleep

A sleep stage equivalent to REM sleep in which brain activity resembles wakefulness despite muscle paralysis.

Periodic limb movement disorder

A sleep disorder involving repetitive involuntary limb movements during sleep.

PGO

An abbreviation for pons geniculate occipital waves, electrical activity associated with REM sleep.

Polysomnograph

The machine used to conduct and record data during a polysomnography sleep study.

Reticular formation

A network in the brainstem that regulates consciousness, alertness, and sleep-wake transitions.

Sleep spindle

A brief burst of brain activity occurring during stage 2 NREM sleep associated with memory consolidation.

Unresponsiveness wakefulness syndrome

A condition previously called vegetative state in which a person appears awake but lacks conscious awareness.

Slow wave sleep

The deepest stage of NREM sleep characterised by delta brain waves and restorative processes.