SciShow: Sleep: Why We Need It and What Happens Without It

  • Sleep is one of the strongest biological urges that we have 

    • You can die faster from sleep deprivation than from food deprivation 

  • 1/3 of our lives 

    • Avg. person spends 25 years asleep 

  • There is no scientific consensus as to why exactly we do sleep

  • Super-ciasmatic nucleus acts like a timer = 1st trigger of sleep 

    • Lives inside of hypothalamus (tiny nut-sized region at the base of your brain) 

    • When you’re exposed to light it releases “awake” hormones like cortisol and suppresses “sleepy” hormones like melatonin 

      • Does the opposite in the dark 

  • Adenosine = a compound in the brain that builds up = 2nd trigger for sleep 

    • Adenosine is a byproduct of your neurons and other cells when they burn up ATP (Adenosine TriPhosphate) 

      • ATP is the main molecule our body uses to store energy 

      • When a bunch of leftover adenosine builds up in the brain you get sleepy 

        • Caffeine works by bonding to the same receptors as adenosine, tricking the body into thinking it’s not tired 

        • When do you do sleep, adenosine levels drop as it’s gradually reabsorbed by your neurons 

          • This is partly what makes you feel rested when you wake up 

  • But why are we wired to sleep??? 

    • All creatures sleep or do a sleep-like thing

    • Many theories (unlikely anyone is the one correct one) ​

      1. Inactivity at night is an evolutionary adaptation that boosts an animals survival rate by keeping it out of danger when it would be most vulnerable 

        • keep still to attract less attention 

        • However: Lions sleep 15 hours a day and giraffes sleep <2 hrs a day 

      2. Sleep conserves energy 

        • procure calories to keep going 

        • humans use about 10% less energy when sleeping than when awake 

          • breathing, body temp, and heart rate all decrease

      3. Sleep provides RESTORATION 

        • When we sleep we: (body stuff) 

          • Grow muscle tissues

          • Cells synthesize proteins 

          • Tissues repair themselves 

          • Growth hormones are released

 

  • Our brains need sleep as much as our bodies do 

  • Sleep allows the brain to rejuvenate and more importantly reorganize = BRAIN PLASTICITY THEORY 

    • Sleep is when our brains replay and store the events of the day 

      • ~ 8 hours for processing and consolidating of new memories 

      • Experiment: People who learned something in the evening, napped, and were tested (12 hrs later) in the morning tested better on the material than those who were taught in the morning and tested (12 hrs later) without sleep 

        • Napping is a good idea! 

      • Sleep helps clear out / forget junk memories from the day as well 

        • When you form memories during the day your brain strengthens the synapses between neurons

          • Learning new things often causes neurons to create new entirely synapses 

          • By tracking the bursts of electrical activity that happen 1000x each night among your billions of neurons scientists have discovered that during sleep both high frequency and low frequency bursts increase while moderate frequency bursts decrease

            • Your brain is choosing to either rev up or calm down the firing between each of those synapses you made when you were awake, ultimately strengthening or weakening each connection

              • When you wake up, the insignificant details about the previous day are probably lost forever

              • Without this daily cleaning process, your brain would face a major energy shortage and space crunch 

                • This function of sleep is like defragging a hard drive 

 

  • The problems of sleeping problems

    • Short term sleep deprivation (even 1 night) throws the amygdala into overdrive which shuts down the Prefrontal Cortex 

      • the PFC controls logical reasoning, executive functioning 

      • When it bypasses the PFC, the sleep deprived brain connects instead to one of the oldest and primitive regions (evolutionarily speaking), the locus coeruleus (the blue spot of your brain; the tissue is actually blue) 

        • The blue spot’s job is to make you instinctively respond to stress and panic 

          • It can interpret anything as a threat 

            • i.e. a swerving car, a terse e-mail, an offhand remark 

            • leaves you anxious and suspicious of everyone and everything 

    • The longer you go without sleep the worse things get 

      • Memory and speech control are the next to suffer 

      • General paranoia can give way to increasingly vivid hallucinations 

        • Theory that this is your brain forcing you into a “waking sleep” 

  • Can a lack of sleep actually kill you? Yes 

  • Sleep is closely related to immune health 

    • Studies have shown a 50% decrease in antibodies in test subjects only moderately sleep deprived for 1 week, exposing them to a host of illnesses 

    • A group of rats deprived of sleep all died within 2 weeks 

    • cause of death was simply exhaustion, nothing was physically wrong with them 

  • The longest documentary case of a person voluntarily staying awake is 264hrs or ~11hrs