Sleep is a very fascinating subject when studying the human brain. It is an altered state of consciousness, a time we can not eat, fight for our survival, or run from a saber tooth tiger. In sleep we have a decreased ability to react to stimuli. Some people loose the ability to react to stimuli much more than others. Out senses are turned of and all our voluntary a actions shut down. Sleep is more easily reversed via stimuli than the state of hibernation or of being comatose. But still it is a time that we are severely vulnerable (enough so we can even have a surgeon cut into us without any pain). Wouldn’t that be a need/trait that would render us unfit in the natural selection game. So why sleep? And ever weirder, why do we turn into delusional trippy zombies without sleep (like in the first few weeks of your new born child’s life – great timing nature).
Sleep science is fairly deep and complex. Here are some interesting factoids about sleep:
- Adenosine is an enzyme/neurotransmitter that is involved in the timing of our sleep and wake states
- The brain releases the hormone melatonin and core body temp gradually decreases (unless you are pre-menopausal – then you are burning up and swimming in sweat)
- Below is what the National Sleep Foundations says about the sleep you need to be healthy
Newborns (0–3 months) 14 to 17 hours Infants (4–11 months) 12 to 15 hours Toddlers (1–2 years) 11 to 14 hours Preschoolers (3–5 years) 10 to 13 hours School-age children (6–13 years) 9 to 11 hours Teenagers (14–17 years) 8 to 10 hours Adults 7 to 9 hours
- Sleep has stages. Stages of REM and NREM, usually four or five of them per night, the order normally being N1 → N2 → N3 → N2 → REM. There is a greater amount of deep sleep (stage N3) earlier in the night, while the proportion of REM sleep increases in the two cycles just before natural awakening.
- The sleep you need as you age decreases but less sleep is may not be responsible for lower cognitive abilities
(From NPR-KUT Austin) Two Guys on Your Head
Many sleep studies are conducted on younger people who need a lot of sleep, in part, because their brains are developing in many different ways. For example, when we are young, we’re forming ideas of who we are. We’re also trying to remember and learn all sorts of different things about the world and our place in it. Our brains are working really hard and sleep helps to consolidate memories and clean out the detritus that lingers between the cells in our brains.In middle age it is very important that we sleep well and maintain healthy sleep patterns also, because this helps to protect our brains in old age. If we don’t get enough sleep in this stage of life, Markman says, by old age there’s broken windows and graffiti all over your brain. As we reach old age there is less “creation of self” going on in our brains, and our brains don’t need as much recovery time. In fact, if we need more sleep in old age, it is likely because we’re sick. So, in some studies, we see a reversal between the amount of sleep people are getting and cognitive functioning. Healthy older adults just don’t need a lot of sleep – and that’s okay.