Restorative theory.
Survival Theory.
Restorative Theory.
It proposes that sleep helps us recover from activities during waking time that use up the body's physical and mental resources. It gives the body an opportunity to:.
Replenish the stores of energy that have been depleted during the day.
Allows damaged cells to be repaired.
Detoxifies various muscles.
During sleep our growth hormones increase which promote body repair and growth. Most people feel tired before they sleep and when they wake they feel more refreshed and energetic.
However according to thus theory, those who are disabled would sleep less but this is not the case. There is also little evidence that we sleep more after an active day. .
Restorative Functions of NREM.
It is believed to be important for restoring and repairing the body. Such as physical growth, tissue repair and recover from the effects of fatigue.
If you don't have NREM sleep you may feel weak, tired and could be in pain in the morning.
Restorative Functions of REM.
It is believed to restore the brain and may have a role in higher order mental functions such as learning.
REM sleep is more abundant in the development of infancy than in childhood.
Survival Theory.
It is proposed that sleep evolved to enhance survival by protecting an organism through making it inactive during the part of the day when it is most dangerous to move about.
While sleeping an organism is not physically active with the environment and is less likely to attract attention of the potential predators. Animals with few natural predators ten to sleep longer (15 hours) as there is no danger. To grazing animals with many predators who only sleep 4 hours.
This theory doesn't explain why sleep involves a loss of awareness as this places the organism at a greater risk.
Characteristics Sleep.
There are two types of sleep:.
Non-rapid-eye movements sleep (NREM sleep).
Rapid-eye movement sleep (REM sleep).
NREM.
One cycle of NREM sleep last for around 70-90 mins and it consists of 4 distinct stages.