Ch 9 - Higher Functions And Sleep Flashcards
Circadian Rhythm
What prepares the body for sleep and wakefulness
25 Hour - Free Running (not influenced by Zeitgebers
24 Hour - Endogenous circadian rhythm
- Controlled by zeitgebers;sunrise, sunset, meal times - External factors
Body Temperature
Sleep pattern is very closely linked to body temp - almost governed by.
Major controller of circadian rhythm
4-6am, body temp lowers (circadian low), where you get the best sleep, most tired, performance lowest
You get the best sleep when your body temp decreases
Higher body temp = disruptive sleep, not restful
Sleep Credits and Debits
8 hours sleep = 16 credits
Maximum 8/16
We lose 1 sleep credit every hour we are awake
Sleep Debit / Deficit
Either staying up to late or up too early will result in sleep debit / deficit
You need roughly 2 hours sleep for every 1 debit / deficit
Performance reduction due to lack of sleep is made worse by altitude
What measures brain activity
EEG - Electroencephaolgram which measures brain waves
5 Stages of sleep
Stage 1 (slow wave/orthodox) - very light sleep, drowsy which is this transitional phase between wakefulness and sleep
Stage 2 (slow wave/orthodox) - Short periods of EEG waves - Most of our sleep is in this stage ~ 50%
Stage 3+4 (slow wave/orthodox) - Deep sleep; relaxed muscles, eyes stationary, slower EEG waves
Stage 5 (paradoxical sleep) - R.E.M. (Rapid eye movement) ~20-25% where we have; dreaming, brain very active (basically awake), eyes constantly moving, basically awake but paralysed
Difference between orthodox and paradoxical sleep
Orthodox sleep repairs and restores cells in the body, refreshes the body and restores tissue. Slow wave and makes up stages 1-4. The more activity you do, the more orthodox sleep you will have as more repairing is needed.
Paradoxical sleep (stage 5/R.E.M.) refreshes the brain, strengthens and organises your memories.
Rebound Effect
The brain and body calculate how much of each type of sleep you need. Paradoxical and orthodox.
Losing R.E.M. Sleep could lead to psychosis which can be very very dangerous
Sleep Cycle
On average ~ 90 minutes (from falling asleep to rem)
First stage of rem is very short only ~ 15 minutes
Duration of R.E.M. Increases throughout the night
4/5 rem cycles per night
Naps and microsleeps
Nap; to be restorative it needs to be at least 10 minutes long. 5 minutes to then fully recover from a nap but performance can be degraded up to 20 minutes later.
Microsleep - eyes can be open, last only 2/3 seconds. Can be when driving and you don’t even know they are happening. Not restorative
Jet Lag (Circadian Rhythm, Transmiridian Desynchronisation)
Fatigue caused by changing time zones.
Worst east bound (west is best)
Recovery time is 90 minutes per day spent in the new time zone
Subjective recovery though
No jet lag from Amsterdam to Johannesburg
<24 hours - stay on your own time zone
>24 hours - adjust to new time zone
Exactly 24 hours - short nap on arrival, get your full 8 hours before next duty time
Sleep Hygiene
When tired your concentration levels are reduced
Inflight you may not be aware of how degraded your performance is
Before going to bed; no exercise, no electronics, alcohol impacts how much rem you get, no food or caffeine too close to bed, black out curtains help a lot
Sleep Disorders
Narcolepsy - can fall asleep any time, anywhere
Sleep Apnoea - stop breathing when you sleep, snorers
Sleep walking/talking (somnambulism/somniloquism) more common in children
Situational insomnia; circumstancial due to noise, caffeine, light - common for aircrew
Clinical insomnia; is long term, caused by chronic stress - tired all day and wide awake at night
Rules for Aircrew
Sleeping pills are not allowed unless under strict supervision of AME
Aircrew should have a proactive attitude to sleep e.g plan, make sure you get enough
Fatigue
Can be caused by metal or physical exertion - can lead to extreme tiredness and illness
working too hard, too much noise, caffeine all wont help
Always a bad thing as it is cumulative and subjective
