Sleeping in order to live
Sleep is necessary for the brain to be able to function and for survival of the entire organism. Sleeping has many functions: growth and regeneration processes, detoxification and wound healing take place in the body – the metabolism is running flat out. Parts of the brain are highly active now as well. They are processing everything the brain has assimilated during the day. Important information is shifted from the short-term into the long-term memory.
Every living creature has a repeating sleep-wake cycle that repeats every 24 hours. The time schedule and control mechanism are dependent on the biological “body clock” or circadian rhythm. Sleep consists of two distinct states: REM sleep (REM = rapid eye movement) and non-REM sleep. Scientists suppose that the optimum sleep duration varies from one person to another – for adults it’s an average of seven to eight hours. The sleep requirement of an adult human doesn’t change for their entire lifetime.
Sleep phases
There are usually four to five sleep cycles through the duration of a healthy sleep. REM sleep is characterised by fast eye movements and often features dreaming. It’s a state below wakefulness, but significantly above deep sleep. Blood pressure and pulse are relatively high, but the skeletal muscles are completely relaxed. Non-REM sleep is classed into several stages, which vary in terms of the amplitude and speed of brainwaves. Phase N3 of non-REM sleep is called deep sleep. It’s mostly in this phase that growth hormones are secreted from the pituitary gland orhypophysis.
Snoozing in the air
All living creatures have to sleep. However their sleep needs vary widely: some animals sleep 20 hours a day, while two hours is enough for others. But what about birds, who spend almost all their lives in the air? Or migratory birds, who cover distances of thousands of kilometres without landing? They sleep too – in flight, as Max Planck scientists have been able to prove with frigate birds. For this project, the birds wear little measuring devices that record their brain activity. Admittedly the birds only sleep just over 40 minutes a day in the air and usually only a few seconds at a time. Normally just one half of the brain sleeps at any given time, the other is awake. In the case of the flying frigate birds, however, sometimes both brain halves are asleep at the same moment. The researchers can even measure short REM phases. REM sleep is something only found in mammals and birds. While in mammals the muscles relax completely, birds are still able to fly, or at least glide.
© Max Planck Institute of Animal Behaviour, Konstanz / Bryson Voirin
The clock that rules the day
In many countries around the world there is summer and winter time – twice a year the clocks are changed by an hour. Many people find this time shift difficult. It’s because of our circadian rhythm, a kind of “internal clock”, that’s active in (almost) every cell of our body, controlled by a network of genes and proteins. It ensures that important physiological processes in the body such as sleeping and waking, blood pressure and body temperature adhere stably to a daily routine, but also can be adapted to new environmental conditions. The most important stimulus here is daylight. Special light-sensitive cells in the eye send information directly to the hypothalamus. But hormones produced by the pituitary gland and the adrenal glands, such as cortisol and adrenalin, play a key role here too. The circadian rhythm is a complex system of which many aspects are still being researched, for instance at the Max Planck Institute for Biophysical Chemistry in Göttingen.
Learning whilst asleep
Our brain has to process a large number of stimuli. It ensures order by storing new information in the long-term memory, grouping similar information together and generalising it. One thing is crucial for this: enough sleep. Even the brain of a baby aged six to eight months allocates words to meanings while sleeping. This has been demonstrated by studies at the Max Planck Institute for Human Cognitive and Brain Sciences: researchers show babies things that are not yet familiar. If these things differ only slightly in form or colour, such as a green cup and a red cup, they are grouped together and in this case both referred to as “cup”. In the learning phase, babies cannot yet order the new things to a group and associate them with the correct category name. That changes after sleeping. Now the brain can group the different cups together under the general term “cup”. So the babies generalised new knowledge while sleeping. The same applies to adults. To secure facts the deep sleep phases are particularly important, while dream phases are used to process sequences of events and emotions.
© polkadot / Adobe Stock
Every living creature has a repeating sleep-wake cycle that repeats every 24 hours. The time schedule and control mechanism are dependent on the biological “body clock” or circadian rhythm. Sleep consists of two distinct states: REM sleep (REM = rapid eye movement) and non-REM sleep. Scientists suppose that the optimum sleep duration varies from one person to another – for adults it’s an average of seven to eight hours. The sleep requirement of an adult human doesn’t change for their entire lifetime.
Sleep phases
There are usually four to five sleep cycles through the duration of a healthy sleep. REM sleep is characterised by fast eye movements and often features dreaming. It’s a state below wakefulness, but significantly above deep sleep. Blood pressure and pulse are relatively high, but the skeletal muscles are completely relaxed. Non-REM sleep is classed into several stages, which vary in terms of the amplitude and speed of brainwaves. Phase N3 of non-REM sleep is called deep sleep. It’s mostly in this phase that growth hormones are secreted from the pituitary gland orhypophysis.
Snoozing in the air
All living creatures have to sleep. However their sleep needs vary widely: some animals sleep 20 hours a day, while two hours is enough for others. But what about birds, who spend almost all their lives in the air? Or migratory birds, who cover distances of thousands of kilometres without landing? They sleep too – in flight, as Max Planck scientists have been able to prove with frigate birds. For this project, the birds wear little measuring devices that record their brain activity. Admittedly the birds only sleep just over 40 minutes a day in the air and usually only a few seconds at a time. Normally just one half of the brain sleeps at any given time, the other is awake. In the case of the flying frigate birds, however, sometimes both brain halves are asleep at the same moment. The researchers can even measure short REM phases. REM sleep is something only found in mammals and birds. While in mammals the muscles relax completely, birds are still able to fly, or at least glide.
The clock that rules the day
In many countries around the world there is summer and winter time – twice a year the clocks are changed by an hour. Many people find this time shift difficult. It’s because of our circadian rhythm, a kind of “internal clock”, that’s active in (almost) every cell of our body, controlled by a network of genes and proteins. It ensures that important physiological processes in the body such as sleeping and waking, blood pressure and body temperature adhere stably to a daily routine, but also can be adapted to new environmental conditions. The most important stimulus here is daylight. Special light-sensitive cells in the eye send information directly to the hypothalamus. But hormones produced by the pituitary gland and the adrenal glands, such as cortisol and adrenalin, play a key role here too. The circadian rhythm is a complex system of which many aspects are still being researched, for instance at the Max Planck Institute for Biophysical Chemistry in Göttingen.
Learning whilst asleep
Our brain has to process a large number of stimuli. It ensures order by storing new information in the long-term memory, grouping similar information together and generalising it. One thing is crucial for this: enough sleep. Even the brain of a baby aged six to eight months allocates words to meanings while sleeping. This has been demonstrated by studies at the Max Planck Institute for Human Cognitive and Brain Sciences: researchers show babies things that are not yet familiar. If these things differ only slightly in form or colour, such as a green cup and a red cup, they are grouped together and in this case both referred to as “cup”. In the learning phase, babies cannot yet order the new things to a group and associate them with the correct category name. That changes after sleeping. Now the brain can group the different cups together under the general term “cup”. So the babies generalised new knowledge while sleeping. The same applies to adults. To secure facts the deep sleep phases are particularly important, while dream phases are used to process sequences of events and emotions.
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