What Do You Know About Sleep?

Why does a giraffe need 4.5 hours of sleep a day, but a chipmunk need 15 hours of sleep a day?

According to the researchers at the UCLA Sleep Disorder Center, one explanation can be found in the different evolutionary way animals have adapted for self-protection and energy conservation. For instance, giraffes only need about 4.5 hours sleep a day because they need to eat most of the time to fuel their giant bodies. By contrast, chipmunks need to sleep more than 15 hours a day as the most energy efficient way of staying safe.

Similarly, it makes evolutionary sense for platypuses to feed less and sleep more than 13 hours because of their high fuel/ caloric crustacean meals. For example, brown bats sleeping more than 19 hours a day is the optimal way of conserving energy as they only need few hours a night to catch their insect prey. As for safety, dolphins sleep with half its brain awake so it can remain aware of its underwater environment, whereas bats or those mammals that sleep in hiding tend to have longer, deeper sleep than those on constant alter.

The answer to our question lies in the different function sleep servers for different mammals, as Allan Rechtschaffen, a renowned sleep researcher, put it: "if sleep doesn't serve an absolutely vital function, it is the greatest mistake evolution ever made."

Some essential fact about sleep you may like to know:

1. Circadian rhythm - your internal 24-hour sleep-wake cycle or your biological clock, is regulated by processes in the brain that respond to how long you've been awake and the changes between light and dark.

2. Melatonin - is a hormone that makes you sleepy. At night, your body responds to the loss of daylight by producing melatonin. During the day, sunlight triggers the brain to inhibit melatonin production so you feel awake and alert.

3. Sleep-wake cycle - your sleep-wake cycle can be disrupted by factors such as nightshift work, traveling across time zones, or irregular sleeping patterns, leaving you feeling groggy, disoriented, and sleepy at inconvenient times. The production of melatonin can also be thrown off when you're deprived of sunlight during the day or exposed to too much artificial light at night, disrupting the sleep-wake cycle and preventing you from getting the sleep you need.

4. Deep-wave Sleep and REM - Our sleep is divided between periods of 'deep-wave sleep' and what is called 'Rapid Eye Movement' ('REM') sleep, that is when the brain is as active as when we are awake, but our voluntary muscles are paralyzed.

5. Researchers at Harvard found that people who had engaged in REM sleep performed better in memory tasks and linguist tests.

6. Sleep helps your memory - Studies have found that sleeping brain appears to repeat a pattern of neuron firing that occurred while the subject was recently awake, as if in sleep the brain were trying to commit to long-term memory what if had learned that day. These studies suggest that memory consolidation may be one function of sleep.

7. Disrupted sleep may harm your health - Researchers at the Woolcock Institute of Medical Research have found that there's a relationship between disrupted sleep and the risk of obesity, the risk of diabetes, and the risk of heart attack. During sleep, certain metabolically active hormones are secreted. So for example growth hormone is secreted during slow wave sleep, this deep sleep. And if you don't have slow wave sleep, then you don't get this growth hormone being secreted.

Question 1 Scientific studies have found that we need sleep to: (A.) recharge our immune system.

One of the greatest mysteries about the human body is why we need sleep. Researchers now propose that one of the functions of sleep is to give the body time and energy to 'recharge' the immune system. We know that people who don't get enough sleep have abnormalities in the functioning of their immune system, including producing fewer white blood cells that help defend against viruses.

Question 2 The term 'sleep apnoea' refer to: (E) prolonged pauses in breathing during sleep.

Sleep apnoea is a condition where the muscles in your throat and upper airway collapse repeatedly while you sleep, preventing you from breathing and partially rousing you from sleep many times during the night. It affects roughly 25 per cent of men and 10 per cent of women over the age of 30, although it's more common in those over 65. Many people pause during breathing while they sleep, but if these interruptions (apnoeas) are longer than normal, from 10 seconds up to as long as a minute, and occur five or more times an hour, then you may have a mild form of Obstructive sleep apnoea (OSA). Moderate OSA is defined as between 15 and 30 apnoeas per hour, and severe OSA as more than 30 apnoeas per hour.

Question 3 Which of the follow way is a good cure for insomnia: (E) get up at the same time every day.

A regular sleeping and rising routine can help overcome insomnia. While advice often centres on going to bed at the same time each night, a regular rising time is actually more important. That means avoiding sleep-ins, regardless of how you slept the night before. Drinking alcohol and exercising close to bedtime can also interfere with sleep. Watching TV before bed, regardless of what you're watching, can interfere with winding down because the light from the screen can be too stimulating. And watching TV in bed is particularly problematic because it can weaken the link you want your brain to make between 'being in bed' and 'being asleep'.

Question 4 Sleepwalking: (A) is more common in people who work night shifts.

Sleepwalking, also known as somnambulism, is more common in shift workers and other people whose sleep patterns regularly change or are frequently disrupted. One theory is that sleep deprivation is the trigger. Sleepwalking usually occurs within an hour or two of falling asleep, during the slow-wave, 'deep sleep' period, not in the rapid eye movement (REM), dreaming phase of sleep. Sedatives don't work very well as treatments for sleepwalking; in fact, sedatives, hypnotics or other medications that alter states of consciousness, as well as alcohol, can trigger sleepwalking. Sleepwalking is an uncommon but well-publicised side effect of the sedative zolpidem (Stilnox). Many children may experience sleepwalking, in fact one child in every six or seven may sleepwalk at some time or other. Most will grow out of it, although one in four cases persists into adulthood.

Question 5 Research has found chilli, jasmine rice and cheese can all help you off to sleep: (A) True.

While many of us enjoy a bit of chocolate while we're chilling out in front of the television, chocolate contains caffeine, which is a stimulant and an enemy of sleep. Interestingly, research has found chilli, jasmine rice and cheese can all help you off to sleep.

So far scientists are unable to answer why we can't sleep, this is partly because we don't know why we need sleep in the first place. The predominant theory of sleep is that the brain demands it. However, for suffers of Fatal Familial Insomnia ('FFI') these research on sleep has been of little help. FFI is an awful disease and as the name suggest it always ends with death. A patient with FFI carries malformed proteins called prions, which attack the patient's thalamus and the damaged thalamus interferes with sleep.