Sleep is a state of altered consciousness in which we become less aware of what’s going on around us. Sleep can take different forms in different animals. Dolphins, for example, sleep just half a brain at a time, and can even continue to swim while asleep.
For humans, sleep involves four stages, called N1, N2, N3 and rapid eye movement (REM). N1 is the lightest stage of sleep. It usually occurs right after you fall asleep, and typically lasts less than 10 minutes. During N2, you sink deeper into sleep. This stage is characterised by brief, high-amplitude brainwaves called ‘K-complexes’ and bursts of lower amplitude waves called ‘sleep spindles’. The N3 stage is the deepest stage of sleep, and is characterised by slow brain waves called delta waves. Finally, during REM sleep your brain activity and breathing rate speed up, and your eyes move quickly in lots of directions. Our most vivid dreams tend to occur in REM sleep, and our brain paralyses our muscles so that we’re unable to act them out. During the night, we continually cycle through these four sleep stages, with a full cycle taking around 90 minutes in adults.
HOW MUCH SLEEP DO WE ACTUALLY NEED?
Denne historien er fra October 2020-utgaven av BBC Focus - Science & Technology.
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Denne historien er fra October 2020-utgaven av BBC Focus - Science & Technology.
Start din 7-dagers gratis prøveperiode på Magzter GOLD for å få tilgang til tusenvis av utvalgte premiumhistorier og 9000+ magasiner og aviser.
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Do We Finally Know How the Egyptian Pyramids Were Built? - A number of breakthrough studies are beginning to paint a picture of how these wonders of the world were built, but much of the story still remains a mystery...
A number of breakthrough studies are beginning to paint a picture of how these wonders of the world were built, but much of the story still remains a mystery...How the Egyptian pyramids were built has long been a mystery. Constructed as tombs for the pharaohs over 4,000 years ago, more than 100 of them remain. The largest one, the Great Pyramid of Giza, was originally 147m tall (482ft). It's made up of about 2.3 million stone blocks, each weighing between 2.5 and 15 tonnes, and would have had to be transported to the building site and lifted into place with techniques available at the time. To put this into context, it's akin to lifting a double-decker London bus to the top of St Pauls Cathedral a few million times.
An Artificial Heart Inspired by Plumbing - Mechanical circulation could revolutionise transplant design and reduce waiting lists
Mechanical circulation could revolutionise transplant design and reduce waiting lists. In July, this artificial heart was successfully implanted, for the first time, into a patient with end-stage heart failure. Built by The Texas Heart Institute (THI) and BiVACOR, the replacement organ has been dubbed the Total Artificial Heart (TAH). Although, being an implant rather than transplant, it's designed to temporarily support patients while they wait for a real heart transplant.
CHANGE THE (BODY) CLOCKS
Why the end of British Summer Time can be a wake-up call for our circadian health
ARE OCTOPUSES SENTIENT?
If you've watched the Netflix documentary My Octopus Teacher or been lucky enough to encounter an octopus in the wild, you'll know there's something special about them.
THE MEXICAN MOLE LIZARD
Imagine what would happen if an earthworm, a lizard, a snake and a mole went on a night out, had too much too much tequila and let their guard down.
ECLIPSES ON DEMAND
Inside an unassuming building, behind a damp car park in Antwerp, Belgium, scientists are teaching two spacecraft to be dance partners for a performance that will take place in front of the Sun.
How light's 'secret code' reveals the story of the cosmos
The starlight we can see tells us alot about the Universe, but it's the parts we can't see that contain the biggest revelations
Major Stonehenge discovery deepens mystery around ancient monument
New findings suggest a key six-tonne stone came from over 450 miles north of the circle
THE UNEXPECTED RETURN OF PNEUMATIC TUBES
Once a pioneering technology that revolutionised deliveries, pneumatic tubes had all but disappeared. Now they're back and enjoying a resurgence
LIVING FOSSILS
FOR SOME CREATURES ALIVE TODAY TIME HAS ALMOST STOOD STILL. MEET THE 'LIVING FOSSILS' THAT GIVE US A GLIMPSE INTO LIFE IN THE DISTANT PAST
