SAC - PSYCH unit 4 aos 1

Circadian rhythms

A biological process that coordinates the timing of body activities over 24 hours, closely aligned with the day-night cycle.

• eg) sleep-wake cycle

Ultradian rhythms (REM and NREM Stages 1–3)

Biological processes that occur in a cycle of less than 24 hours. Within an eight-hour sleep episode, a person typically experiences about five 90-minute ultradian cycles

NREM (Non-Rapid Eye Movement) (Ultradian Rhythms)

Consists of three stages characterised by a progressive decline in physiological activity (e.g., heart rate and temperature drop).

• N1 is the light transitional phase

• N2 is light sleep where psychological processes slow

• N3 is deep, slow-wave sleep

REM (Rapid Eye Movement) (Circadian Rhythm)

A stage characterised by quick darting of the eyes behind closed eyelids and an increase in psychological activity. it is often associated with dreaming/mind repairs

Suprachiasmatic Nucleus (SCN):

A small part of the hypothalamus that acts as the brain's master body clock.

It receives light signals from the eyes and coordinates body activities to a daily schedule of sleep and wakefulness

Melatonin

A hormone released by the pineal gland that induces drowsiness and decreases cell activity to prepare the body for sleep.

• When the SCN detects low light, it signals the pineal gland to increase melatonin secretion, promoting sleep.

• Bright light detection causes the SCN to inhibit melatonin release, promoting wakefulness.

Newborns (0–3 months):

Require the most sleep

• approx 14–17 hours.

About 50% of this is REM sleep, which is thought to boost rapid brain growth, development, and memory consolidation

Adolescents (14–17 years):

Require roughly 8–10 hours of sleep.

They experience a circadian phase delay, where melatonin is released roughly 1 to 2 hours later than in childhood, pushing their natural sleep onset time later into the night

Older Adults (65+ years):

Generally require 7–8 hours of sleep.

They often experience a decline in N3 deep sleep and may suffer from Advanced Sleep Phase Disorder, where they feel sleepy earlier in the evening and wake earlier in the morning.

Explanation for Changes in sleep demands and patterns

As humans age, the total amount of sleep needed decreases, and the proportion of REM sleep declines from 50% in infancy to approx 20% in adulthood. Older age is often associated with reduced sleep efficiency—the percentage of time in bed spent actually asleep.

Partial Sleep Deprivation:

The experience of achieving inadequate sleep in terms of either quantity (total hours) or quality (e.g., fragmented sleep)

Affective Functioning:

Refers to emotional regulation.

Deprivation can lead to mood swings, irritability, difficulty controlling emotions, or crying for no apparent reason.

Behavioural Functioning:

Refers to observable actions.

Effects include slower reaction times, clumsiness, impulsivity, and risk-taking.

Cognitive Functioning

Refers to mental processing.

Effects include poor concentration, memory lapses, reduced alertness, and impaired problem-solving abilities.

Comparison to Blood Alcohol Concentration (BAC)

• Research indicates that 17 hours of wakefulness (partial deprivation) results in cognitive and affective impairments equivalent to a BAC of 0.05.

• A full 24 hours of sleep deprivation (one full night) results in impairments comparable to a BAC of 0.10, double the legal driving limit.

Sleep Hygiene

Beneficial sleep-related behaviours and environmental conditions practiced consistently to improve sleep quality and quantity

Zeitgebers:

Environmental cues that synchronize and regulate the body’s circadian rhythm

Daylight and Blue Light (Zeitgebers)

Daylight is the primary zeitgeber for the human circadian rhythm.

Blue light (screens) is particularly effective at suppressing melatonin.

Good hygiene involves exposing oneself to natural light in the morning to reset the clock and avoiding blue light at night to allow melatonin production.

Temperature: (Zeitgebers)

Core body temperature must drop to initiate and maintain sleep.

Good hygiene includes keeping the bedroom cool.

• warm bath or shower before bed can help by causing the core temperature to drop afterward

• exercise right before bed raises the core temperature and can inhibit sleep onset.

Eating and Drinking Patterns: (Zeitgebers)

The timing of meals influences peripheral body clocks in tissues.

Consistency in meal times helps keep these clocks synchronized with the SCN;

• eating at irregular times (like midnight) can disrupt the circadian rhythm.

Quantitative Data:

non-numerical, descriptive information. Examples include video monitoring (visual/audio records of sleep-talking or movement) or individual survey comments regarding how a person felt upon waking

Logbooks & Authentication

A logbook is used to record data progressively, serving as authentication that the data was generated or collated by the student according to scientific protocols. (subjective)

sleep-wake cycle

a daily biological process that coordinates the timing of being asleep and being awake over a roughly 24-hour period.

It is primarily categorised as a circadian rhythm, which allows the body to synchronise its internal functioning with the external environment's day-night cycle.

Circadian sleep rhythm disorders

Sleep disturbances caused by a mismatch between an individual's internal biological clock and the external environment’s required sleep-wake schedule

Types:

• shift work

• DSPS delayed sleep phase syndrome

• ASPD advanced sleep phase disorder.

treated by bright light therapy.

DSPS - Delayed sleep phase syndrone

Circadian rhythm disorder

• delay in the timing of sleep onset and awakening compared with the timing that is desired.

ASPD- advanced sleep phase disorder

Circadian rhythm disorder

• advance in the timing of sleep onset and awakening compared with the timing that is desired.

AIFS Finding: Health guidelines recommend 8–10 hours of sleep for adolescents aged 14–17. The AIFS reports that half of 16–17 year-olds and one-quarter of 12–15 year-olds do not meet these minimum requirements on school nights

60.3% of the Monivae students achieve 8 or more hours of sleep, approximately 40% are achieving 7 hours or less, placing them below the recommended threshold

Age Trend: Both sources show sleep duration decreases with age.

• Monivae's Figure 1 shows bedtimes getting progressively later, peaking at age 16 with an average bedtime of 11:30 PM

AIFS Finding: The report identifies a "yoyo" pattern where teens attempt to "catch up" on sleep by sleeping longer on weekends. This pattern increases with age and disrupts the circadian sleep-wake cycle

• Monivae Data: This is explicitly supported by Figure 4, which shows that the percentage of students who sleep in on weekends increases significantly with age.

• At age 16, roughly 75% of students respond "Yes" to sleeping in. One individual case study reports sleeping in for more than 4 hours past their usual wake-up time on weekends

Life Demands: The AIFS notes that homework and busy after-school schedules often displace sleep time.

48.2% of Monivae students (28 out of 58) "Agree" or "Strongly Agree" that the demands of sport, work, and studying prevent them from getting enough sleep

Screen Use and Blue Light: The AIFS highlights that nearly all homework is digital, and exposure to blue light in the evening impacts sleep duration.

Monivae data shows high levels of this risk factor: 56.9% of students use screens within 15 minutes of trying to sleep, and 55.2% use their phones while laying in bed "Every day"

Caffeine: AIFS suggests caffeine impacts sleep duration for 14–15 year-olds.

Monivae data shows that while 53.5% don't drink caffeine, 13.8% consume it within 2 hours of bedtime, which can interfere with sleep onset

Mental Health: The AIFS confirms that insufficient sleep is linked to symptoms of anxiety and depression

60% of Monivae students withhese symptoms do not meet sleep guidelines

Summary Table of Key Comparisons

Feature	AIFS National Finding	Monivae College Data
Insufficient Sleep	50% of 16-17 year-olds	~40% of the sample
Weekend Catch-up	"Yoyo" pattern increases with age	"Sleeping in" peaks at 75% for 16-year-olds
Technology Use	Internet/Blue light displaces sleep	56.9% use screens <15 mins before bed
Life Pressures	Homework and busy schedules	48.2% feel demands prevent enough sleep
Physical Activity	Sport associated with longer sleep	72.4% meet exercise guidelines (3-5+ hours)