Psych Unit 4 – Ch6 The Demand for Sleep

Question-and-Answer flashcards covering psychological constructs of sleep, measurement techniques (EEG, EMG, EOG), circadian and ultradian rhythms, sleep stages, physiological features, and lifespan changes.

What is sleep classified as in psychology?

A naturally occurring altered state of consciousness (ASC) and a psychological construct.

Define a psychological construct.

An explanatory model for processes (e.g., love, stress, consciousness) that cannot be directly observed or measured.

What is consciousness?

Our personal awareness of internal and external environments.

Along what does consciousness vary?

A continuum from focused alertness to coma.

Define Normal Waking Consciousness (NWC).

Being awake and aware of external objects and one’s own sensations and existence.

What are Altered States of Consciousness (ASCs)?

States distinctly different from NWC in awareness and experience; they may be naturally occurring (e.g., sleep) or deliberately induced (e.g., meditation).

Provide the operational definition of sleep.

A reversible behavioural state with greatly reduced perceptual experience and responsiveness.

Why are EEG, EMG, and EOG considered objective measures?

They detect, amplify and record electrical activity, producing data independent of personal opinion.

What does an electroencephalograph (EEG) measure?

Electrical activity of the brain in the form of brain-waves.

What does an electromyograph (EMG) measure?

Electrical activity (tension) of skeletal muscles.

What does an electro-oculograph (EOG) measure?

Electrical activity of the muscles that move the eyes.

In EEG terminology, what do ‘frequency’ and ‘amplitude’ mean?

Frequency = number of waves per second; amplitude = height (peak-to-trough size) of waves.

Identify the brain-wave characteristics of beta waves.

High frequency, very low amplitude; typical of alert wakefulness.

Identify the brain-wave characteristics of alpha waves.

Moderately high frequency, low amplitude; relaxed wakefulness or stage 1 light sleep.

Identify the brain-wave characteristics of theta waves.

Medium frequency, mixed (high & low) amplitude; stage 2 light sleep and early stage 3.

Identify the brain-wave characteristics of delta waves.

Low frequency, high amplitude; deepest NREM (stage 3) sleep.

How do EEG patterns in REM compare to beta waves?

Both show low amplitude and high frequency, but REM waves often have a saw-tooth appearance.

What does the EMG reveal during REM sleep?

Very little or no muscle activity – evidence of sleep paralysis.

What key information can a sleep diary provide?

Bedtime, sleep onset latency, awakenings, wake time, daily behaviours (diet, exercise, meds, alcohol, dreams).

Give two observations often recorded via video monitoring in a sleep lab.

Posture changes and parasomnias such as sleepwalking or night terrors.

Define a circadian rhythm.

A biological process cycling about once every 24 hours (e.g., sleep-wake cycle, body temperature).

Define an ultradian rhythm.

A recurrent cycle shorter than 24 hours, such as the 90-minute NREM/REM sleep cycle.

What is the role of the suprachiasmatic nucleus (SCN)?

It acts as the master biological clock, using light input to regulate the sleep-wake cycle, body temperature and melatonin release.

How does melatonin secretion relate to light?

Low light triggers increased melatonin (sleepiness); bright/blue light suppresses melatonin (alertness).

Why does blue light before bedtime hinder sleep onset?

Blue wavelengths inhibit melatonin release via the SCN, delaying sleepiness.

What happens to core body temperature as drowsiness increases?

It decreases; lowest temperature occurs in the early morning hours.

What did ‘sleep-in-a-cave’ studies reveal about endogenous clocks?

Without external light, humans still show a sleep-wake cycle that lengthens to ~25 hours, proving an internal pacemaker.

What is sleep pressure and how can it be reduced?

The buildup of the need for sleep during wakefulness; napping temporarily lowers it.

How long is a typical NREM/REM cycle and how many occur per night?

About 90 minutes; usually 4–5 cycles in an 8–9 hour sleep episode.

List two defining features of Stage 1 NREM sleep.

Lasts 5–10 min; easily awakened; alpha replaced by theta; hypnic jerks common.

List two defining features of Stage 2 NREM sleep.

Lasts ~20 min first cycle; 50 % of total sleep; theta waves with sleep spindles/K-complexes; still light sleep.

List two defining features of Stage 3 NREM sleep.

Delta waves dominate (>50 %); very difficult to awaken; heart & breathing slow; parasomnias may occur.

Give three physiological features of REM sleep.

Rapid eye movements, beta-like EEG, muscle atonia (paralysis); vivid dreaming likely.

Why is REM called ‘paradoxical sleep’?

Internally active brain/body systems contrast with externally inactive, paralysed muscles.

Describe the pattern of REM and deep NREM sleep across the night.

Deep Stage 3 NREM is prominent early then fades; REM periods lengthen toward morning.

What is a hypnogram?

A graph showing stages of sleep across time, illustrating ultradian cycles during a sleep episode.

State the trend in total sleep time across the lifespan.

Total sleep decreases from ~16 h (infant) to ~7–8 h (adult) to ~6 h (elderly).

State the trend in REM percentage from infancy to adulthood.

REM falls from ~50 % (newborn) to ~20 % (adult).

Why do newborns spend about half their sleep in REM?

REM provides neural stimulation essential for rapid brain growth and development.

What proportion of sleep is deep NREM (Stage 3) in elderly adults?

Very little or none; they spend more time in lighter NREM 1 & 2 with frequent awakenings.

What biological shift occurs in adolescent sleep?

A 1–2 hour melatonin release delay causing later sleep onset and wake times.

How does blue light act as a zeitgeber affecting sleep?

It signals the SCN that it is ‘daytime,’ suppressing melatonin and delaying sleep onset, reducing sleep quality and quantity.

Compare REM and NREM duration in a healthy adult hypnogram.

REM sessions lengthen across cycles while NREM (especially Stage 3) shortens.

Provide two differences you would expect between an adolescent and an elderly hypnogram.

Adolescent: more REM cycles and more deep NREM; Elderly: less REM, minimal deep NREM, more awakenings.