Seminar 7 Flashcards
What is sleep?
A particular state of consciousness
Stages of sleep
There are five distinct stages of sleep characterised by the electrical activity of the brain as detected by EEG
Stage 1
Non-REM sleep
Transition from wakefulness to sleep, and lasts from 1 to 7 minutes
Stage 2
First stage of “real” sleep
EEG shows high-frequency bursts of activity known as “sleep spindles
Stages 3 and 4
After 30 to 45 minutes after going to sleep
Stage 4 is the deepest stage
Heart rate, respiration, temperature and blood flow to the brain decrease and growth hormone is released, controlling levels of metabolism, physical growth and brain development
REM sleep
Brain activity is very similar to that when you are awake
This is the main dreaming stage.
Functions of sleep stages
REM Memory consolidation and learning Psychological wellbeing Emotional learning Motivation Coping with stress Mood regulation
Sleep regulation: two-factor model
Homeostatic regulation: Process S
sleep need
Sleep-wake circadian clock: Process C
sleep urge
Homeostatic regulation Process S
Controlled by hypothalamus
Sleep-wake circadian clock Process C
Controlled by suprachiasmatic nucleus (SCN)
Circadian rhythms
Evening person (20%) Morning person (10%)
Sleep requirement
New born children are “sleep machines”, they sleep 17 hours
4-year-old 10 hours
Adolescents need about 9 hours, and tend to go to bed later
Adults (over 20) need 7-8 hours
Not true that older people need less sleep
Melatonin
Melatonin secretion is adversely affected by caffeine
Much more than a sleep promoting hormone
Strong cancer prevention effect
Sleep deficit
Hormonal changes → increased appetite, blood sugar irregularities
Sleep deprivation
If you are awake for more than 18 hours, you have impaired reaction speed, memory, decision-making capacity, cognitive speed and spatial orientation
