The Real Reason You Can't Function Without Sleep

An upside-down jellyfish has no brain, but at night it sleeps. Its pulsing slows down, it's slower to react, and if you keep it up all night, it's less active the next day. Almost every animal studied closely seems to sleep, and you spend about a third of your life asleep. So what is sleep for? A calm look at what happens in your brain at night, what makes you sleepy, what happens without sleep, what sleep does for memory, whether it cleans your brain, and how dolphins, frigatebirds, elephants, bats and whales do it. Subscribe for more about the body:    / @anatomyatlas3d   Chapters 0:00 No brain, still sleeps 1:08 How do you know a jellyfish is asleep? 2:17 What happens in your brain at night? 3:41 What makes you sleepy? 5:02 What if you don't sleep? 6:47 What does sleep do for memory? 8:07 Does sleep clean your brain? 9:26 How do other animals sleep? 10:23 So why do we sleep? Main sources The jellyfish Cassiopea exhibits a sleep-like state (Nath et al. 2017, Current Biology) https://pmc.ncbi.nlm.nih.gov/articles... Upside-down jellyfish (Australian Museum) https://australian.museum/learn/anima... Is sleep essential? (Cirelli & Tononi 2008, PLoS Biology) https://journals.plos.org/plosbiology... Do all animals sleep? (Siegel 2008, Trends in Neurosciences) https://teams.semel.ucla.edu/sites/de... Brain basics: understanding sleep (NINDS) https://www.ninds.nih.gov/health-info... Physiology, sleep stages (StatPearls) https://www.ncbi.nlm.nih.gov/books/NB... 86 billion neurons (Azevedo et al. 2009) https://pubmed.ncbi.nlm.nih.gov/19226... The two-process model, a reappraisal (Borbély et al. 2016) https://pmc.ncbi.nlm.nih.gov/articles... Adenosine and sleep in cats (Porkka-Heiskanen et al. 1997, Science) https://pubmed.ncbi.nlm.nih.gov/9157887/ Caffeine and sleep (Reichert et al. 2022) https://pmc.ncbi.nlm.nih.gov/articles... The body clock's own period (Czeisler et al. 1999, Science) https://pubmed.ncbi.nlm.nih.gov/10381... Circadian rhythms (NIGMS) https://nigms.nih.gov/education/fact-... Randy Gardner's 264 hours (Gulevich, Dement & Johnson 1966) https://jamanetwork.com/journals/jama... Sleep deprivation and Randy Gardner (Coren, Psychiatric Times) https://www.psychiatrictimes.com/view... Sleep deprivation in the rat (Everson, Bergmann & Rechtschaffen 1989, Sleep) https://academic.oup.com/sleep/articl... Sleep loss and the gut in flies (Vaccaro et al. 2020, Cell) https://www.cell.com/cell/fulltext/S0... Obliviscence during sleep and waking (Jenkins & Dallenbach 1924) https://www.jstor.org/stable/1414040 Replay of place cells in sleep (Wilson & McNaughton 1994, Science) https://pubmed.ncbi.nlm.nih.gov/8036517/ Replay in slow-wave sleep (Lee & Wilson 2002, Neuron) https://www.janelia.org/publication/m... Synapses shrink in sleep (de Vivo et al. 2017, Science) https://pubmed.ncbi.nlm.nih.gov/28154... Sleep drives clearance from the brain (Xie et al. 2013, Science) https://www.science.org/doi/10.1126/s... Brain waves, blood and fluid in sleep (Fultz et al. 2019, Science) https://www.science.org/doi/10.1126/s... Brain clearance is reduced in sleep (Miao et al. 2024, Nature Neuroscience) https://www.nature.com/articles/s4159... Sleep and a vaccine (Lange et al. 2003) https://pubmed.ncbi.nlm.nih.gov/14508... Sleep in cetaceans (Lyamin et al. 2008) https://teams.semel.ucla.edu/sites/de... Frigatebirds sleep in flight (Rattenborg et al. 2016, Nature Communications) https://www.nature.com/articles/ncomm... Wild elephants (Gravett et al. 2017, PLOS ONE) https://www.sciencedaily.com/releases... Sperm whales drifting off (University of St Andrews) https://news.st-andrews.ac.uk/archive...