Sleep Flashcards
What is sleep?
A periodic, natural, reversible behavioural state of perceptual disengagement from and unresponsiveness to the environment.
What is sleep characterised by?
- Sustained immobility or inactivity
- characteristic posture
- reduced responsivity to external stimuli
How is sleep different from anaesthetic and being in a coma?
Sleep is easily reversible.
How do dolphins engage in sleep and how does this relate to the immobility characteristic?
They engage in uni-hemisphere sleep which allows them to still get up to surface to get water and shows that we can sleep without being completely immobile.
How does characteristic posture of sleep vary?
It depends on whether the anima is prey or predator - prey will sleep in a position where it is easy to get up and away to avoid danger whereas predators like humans can sleep easily laying down as they do not have this threat.
Also it depends on the anatomy of the animal as animals like horses find it hard to get down onto the floor and get back up again so it is easier for them to sleep standing up.
How does reduced responsivity during sleep vary?
Adults are more easily awaken than children as they need to listen out to children crying and look after them, but also it depends on individual differences, some people are naturally heavy sleepers whilst others aren’t.
Why do we sleep according to Moruzzi, 1972?
Restoration - being awake disrupts homeostasis and being asleep restores this. Clearance of toxic waste products is also twice as fast during sleep, and slow oscillations mean it is a short period of rest for neurons.
Why do we sleep according to Seigel, 2009?
Adaptation - sleep follows our evolution, we don’t see well at night which means we are most vulnerable at this time so sleep evolved to prevent accidents and predation at night. Also, sleep saves energy that we can use during the day and allows awakening when needed.
Throughout species what causes and do not cause differences in sleep duration?
Not causes:
- Size of animal
- Exercise/ activity eg. sloths sleep 20h p/d but barely move whereas horses run a lot and only need 3
. however they may be a little increase in humans
Are causes:
- Species with high metabolic demands sleep more for example horses eat straw which requires a long time to digest which they cannot do whilst asleep
What determines whether we are a night owl or early bird?
It all depends on our chronotype
- In general the older you get the earlier you wake up - our chronotype shifts over our lifetime
- Can be determined by genes - 40-60% of variants of chronotype depend on genes (length of the per3 gene and whether it is 4 or 5 repeats predicts dinural preference)
- Once again is just due to individual difference in a lot of cases
What is social jet lag?
When you have to wake up out of your circadian rhythm and you have a sleep deficit eg. if you are a night owl but work requires you to be up at 6am every day, you will encounter social jet lag.
What effects do you encounter with sleep deprivation (in the case of Randy Gardner, 1965)?
- Irritable
- Nauseated
- Memory problems
- Mild delusions
- Overwhelming fatigue
- Tremors
- Language problems
- Mood
- Reduced attention
How long does it take to recover from sleep deprivation?
You can normalise very quickly and return to original sleep patterns after a day or two, which show restoration theories to not be as true as originally thought because you would expect a lot longer recovery period. This is not true for some animals deprived of sleep however.
What evidence does sleep deprivation have for restoration theory?
If you work several night shifts in a row then you end up with sleep deficits, they accumulate over time.
What do we mean when we say sleep is multifactorial?
No single theory of sleep is completely satisfactory. It originally served to keep us quiet and still at night but now other functions that work best when we are quiet and still have piggy backed on to it.
How can we measure sleep?
- Patient reported outcomes eg. sleep diaries and questionnaires
- Actigraphy eg. recording motor activity during sleep
- Polysomnography (PSG)
Why is actigraphy not completely reliable as a measure of sleep?
Activity varies a lot within sleep eg. people who sleep walk or even just turning over.
How does PSG work?
It uses an EEG to measure brain activity, EMG to measure muscle activation - particularly facial muscles, and an EOG to measure eye movements.
What do delta waves show on an EEG?
Slow and deep sleep
What do theta waves show on an EEG?
Drowsy - can occur both during sleep and wake
What do alpha waves show on an EEG?
Relaxed wakefulness
What do beta/gamma waves show on an EEG?
Awake, alert, and excited
In order of increased amplitude, what are the different EEG rhythms?
- Beta/gamma
- Alpha
- Theta
- Delta
In order of increased frequency, what are the different EEG rhythms?
- Delta
- Theta
- Alpha
- Beta/Gamma
What are spindles and ripples in EEG rhythms?
These occur in light sleep and are linked to memory consolidation