Purpose Of Sleep Flashcards
Total sleep time
The amount of time spent asleep throughout one night including both REM and NREM sleep.
REM sleep
One of the two major phases of sleep that is characterised by rapid jerking eye movements and dreaming.
2 theories about the purpose of sleep
Restorative theory
Evolutionary theory
Restorative theory
Sleep replenishes our bodies and allows us to recharge depleted energy resources. REM replenishes the mind, NREM replenishes the body.
Evidence of restorative theory
– Marathon runners spend more time in
NREM sleep stages 3 and 4
– sleep activates growth and increases immunity
– cognitive decline occurs with sleep deprivation
2 Criticisms of restorative theory
Bedridden
Assumption
Evolutionary theory
Sleep is an evolutionary response that adapts based on the demands of how much food we need, our energy requirements and our safety when we sleep. Animals such as cows graze, they therefore get little sleep because they need more time to find and consume food. Animals vulnerable to predators sleep more because they are inactive and therefore hide safely.
Evidence of evolutionary theory
There is a sequential pattern that demonstrates that the energy requirements of animals and number of predators correlates with sleep requirements. Sleep conserves energy, so hibernation is important when food is scarce in the Winter months.
2 Criticisms of evolutionary theory
The evolutionary theory has attracted criticism including the assumptions that sleep is:
> very useful but not ESSENTIAL. This theory does not explain why we must have sleep. All species sleep, despite the amount of food (abundant or scarce) or danger they are in.
> A way to HIDE safely from predators. For animals that are highly preyed upon, sleeping can be dangerous. The loss of awareness during sleep makes the animal very vulnerable to predators and unlikely to be able to respond to danger.
Assumption criticism
The assumption that more sleep is needed to recover when we are physically active. Unless we partake in extreme physical activities, there is little evidence that we need more sleep when we exercise. A review of research in this area concluded that we tend to sleep longer – by about 10 minutes – on days we have exercised, which is a small di erence from the days we don’t exercise.
Bedridden criticism
If this assumption is true, we might expect that those who do little exercise, including people who are disabled or con ned to bed, would sleep less, but there is no evidence to support this statement: bedridden people show sleep patterns that are similar to those of normally active individuals. The need for sleep is not reduced with lack of exercise.
Memory Consolidation Theory
The purpose of sleep is to create new and lasting memories from the day. Sleep allows time for the brain to process and transfer information into long-term memory
