Discuss the nature of sleep (24 marks)
Numerous things happen in your body while you sleep, we have many stages in which our body goes through in a 90 minute cycle. We have non-REM stages of sleep and REM stages of sleep. REM stands for rapid eye movement. You go through three phases before reaching REM sleep. Stage 1: Your eyes are closed, but it's easy to wake you up and this will last for 5 to 10 minutes. Stage 2: You are in light sleep. Your heart rate slows and your body temperature drops. Your body is getting ready for deep sleep. Stages 3: This is the deep sleep stage. It's harder to rouse you during this stage, and if someone woke you up, you would feel disoriented for a few minutes. Then comes REM sleep, where your heart rate and breathing quickens and as your brain is more active most of your intense dreams take place during this stage.
The amount of time we spend each day sleeping declines throughout our lifetime. As humans grow from infancy to old age there are major changes in the amount and kind of sleep experienced. Babies sleep a lot more than children (spending from 16 to 20 hours asleep each day) and adults also have different sleep patterns and different stages of sleep. They tend to sleep about 16 hours a day. But their sleep is not continuous. By the age of six months a circadian rhythm has become recognized. By the age of five, children have EEG patterns like those of adults but they are still sleeping more and having more REM activity (for brain development). During childhood, the need for sleep decreases, but in adolescence increases, to about 9/10 hours a night. Circadian rhythms change so that teenagers feel naturally awake later at night and have more difficulty getting up early.
Adult sleep is typically about eight hours a night, with 25% REM sleep. With increased age, the pattern of sleep changes; REM sleep decreases to about 20% of total sleep time. Older people also experience a phase advance of circadian rhythms – feeling...