What Is Sleep?

God bless whoever invented sleep, the cloak that covers all human thoughts. It is the food that satisfies hunger, the water that quenches thirst, the fire that warms cold, the cold that reduces heat, and, lastly the common currency which can buy anything, the balance and compensating weight that makes the shepherd equal to the king, and the simpleton equal to the sage.

- Miguel de Cervantes, Don Quixote, II (1615)

Podcast of the Day

Why do we Sleep? At first glance, it seems a silly question but actually it is one that’s been baffling scientists for decades. We spend a third of our lives asleep, but sleep science hasn’t got much further than being sure that we sleep because we get sleepy.

As Mike falls into a deep slumber to the sound of his own recording voice, we will find out exactly what happens when we sleep, from circadian clocks to sleep spindles to the famous REM, and how we have thought about this dark and private side of our lives across ages and cultures.

We explore conflicting theories about the purpose of sleep. One theory is that we developed our sleep patterns to allow our body and mind to repair itself at night. While we know our body grows and heals while we sleep, we know much less about what our brain is doing and a century after Freud and Jung’s explanations, we’re still far from scientific consensus on what dreams are for. Are we consolidating memories? Are we rehearsing our responses to threatening situations? Or is it all random imagery created by an organ that is designed to be awake and can never fully shut down? Another theory is that while our bodies use the opportunity while we are asleep for restoration, it is not why we evolved to sleep around eight hours a day. Could it be as simple as we sleep because our ancestors didn’t need to be awake any longer?

Listen to The Why Factor episode on Sleep

Video of the Day

Short Article of the Day

Sleep accounts for one-quarter to one-third of the human lifespan. But what exactly happens when you sleep?

Before the 1950s, most people believed sleep was a passive activity during which the body and brain were dormant. “But it turns out that sleep is a period during which the brain is engaged in a number of activities necessary to life—which are closely linked to quality of life,” says Johns Hopkins sleep expert and neurologist Mark Wu, M.D., Ph.D. Researchers like Wu are spending many of their waking hours trying to learn more about these processes and how they affect mental and physical health. Here is a glimpse into the powerful (often surprising) findings of sleep researchers—and what they’re still trying to discover about the science of sleep..

Continue reading the John Hopkins Medicine article on The Science of Sleep

Further Reading

Sleep is a naturally recurring state of mind and body, characterized by altered consciousness, relatively inhibited sensory activity, inhibition of nearly all voluntary muscles, and reduced interactions with surroundings. It is distinguished from wakefulness by a decreased ability to react to stimuli, but is more easily reversed than the state of being comatose. Sleep occurs in repeating periods, in which the body alternates between two distinct modes known as non-REM and REM sleep. Although REM stands for "rapid eye movement", this mode of sleep has many other aspects, including virtual paralysis of the body. A well-known feature of sleep is the dream, an experience typically recounted in narrative form, which resembles waking life while in progress, but which usually can later be distinguished as fantasy.

During sleep, most of the body's systems are in an anabolic state, helping to restore the immune, nervous, skeletal, and muscular systems; these are vital processes that maintain mood, memory, and cognitive performance, and play a large role in the function of the endocrine and immune systems. The internal circadian clock promotes sleep daily at night. The diverse purposes and mechanisms of sleep are the subject of substantial ongoing research...

Continue reading the Wikipedia article on Sleep

Related Topics

 CognitionConsciousnessDreams | The Human Body | Neuroscience | Psychology

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