purpose and function of sleep To start whats

purpose and function of sleep To start - what’s your opinion? What is the purpose of sleep? Learning Intentions: 1. Understand reasons why we sleep 2. Outline and evaluate the restoration and evolutionary theories of sleep

Why do we need sleep? Some ideas behind why we may need sleep: Protect ourselves from danger Conserve energy Restore and repair damage to neurons in the brain, and to the body’s tissues and cells Process memories and information learnt during the day Remove waste products built up on the body’s muscles Enable physical growth and development Maintain proper functioning of the nervous system Maintain normal cognitive functioning

Restoration Theory Sleep provides time to help us recover from depleting activities during waking time that use the body’s physical & mental resources. sleep replenishes & store energy Allows time to repair damaged cells & detoxifies muscles (rid the muscles of waste products). This view is supported by: people who are sick sleep for a longer period of time to recover. People who feel tired before sleep, feel more energetic and refreshed upon waking.

Restoration Theory Research evidence to support this theory includes: Studies on rats showed a break down of bodily tissues & death within 3 weeks of sleep deprivation Sleep laboratory studies show sleep is a period of physiological rest. They have also found that a growth hormone is secreted during sleep to promote bodily repairs.

Restoration Theory REM and NREM have different functions according to restoration theory: NREM – restore & repair the body REM- restore brain, higher mental functioning in learning & memory REM is important to infants as it plays a crucial role in developing brains REM may help preserve important connections between neuronal pathways in the brain. REM may assist in consolidating memories & newly learnt information. For example, physical growth, tissue repair and recovery from the effects of fatigue occur during stages 3 and 4 (deep sleep) of NREM sleep, and brain growth and restoration occur during REM

Restoration Theory REM Rebound REM sleep seems to serve as an important biological need. In sleep laboratories, people have been woken up each time they lapsed into REM sleep, with no obvious illeffects. However, when they were allowed to sleep uninterrupted REM periods of sleep, they spent more time than they normally would in the REM stage. They seemed to have needed to make up for the lost REM sleep. This is called a REM rebound where you spend more time in REM immediately after a loss of REM to catching up on this lost REM sleep.

Evolutionary Theory Proposes that sleep evolved to enhance survival by protecting an organism through making it inactive when it is most dangerous. Therefore once an organism has fulfilled all its survival functions such as eating, drinking, caring for its young and reproducing, it must spend the rest of its time conserving energy, hidden and protected from predators. Humans are visual animals who need light for survival (eg. Finding food) Sleep prevents animals from attracting attention

Evolutionary Theory Research evidence comes from: Behaviour & sleep-waking cycles of different species. Animals who have fewer natural predators (lions, gorillas) sleep more (15 hrs). Animals that cannot escape danger and hide away will sleep for shorter periods a day.

Evaluation of Theories • Restorative Theory: What do you think some of the limitations of restorative theory are? • • • Evolutionary Theory: People and animals are subject to greater danger when asleep A simplistic view of sleep Fails to explain why we suffer psychologically and physiologically when we do not get enough sleep OR Why sleep involves a lack of awareness since a loss of consciousness increases an organisms risk.

Reflection and Homework What if… You weren't allowed to know what you've learnt today? Everything I’ve told you today was false? Homework - complete your evolutionary theory worksheet