Dreaming Sleep Disorders We all have internal time clocks Some species of birds some other animals have what are known as circannual rhythms These rhythms last about a year They re important for generating seasonal changes like migration and reproduction Humans have circadian rhythms which last about a day The one that comes most easily to mind is the rhythm responsible for wakefulness and sleep we also have one for body temperature hormone production drug sensitivity etc If you pull an all nighter as morning comes you perk up more That s because you approach your wakefulness phase again Differences in sleep and wakefulness phases in age The very young and the very old tend to fall asleep early and wake early Teens early 20s you see that phase shift go to sleep later and wake later These rhythms persist in the absence of light but light is critical for resetting our rhythms Biological clock is really an internal mechanism that controls behavior that occurs on a regular schedule This kind of light that resets it is called the Zeitgeber Our biological clock has a free running rhythm that is not exactly 24 hours it s a little longer than 24 hours But externally everything is set to function on a 24 hour day it s closest to our internal clock What if there is no light Could one alter someone s internal clock extending it An experiment testing this is putting people in the mammoth caves in Kentucky where it s truly dark Bottom line is that one can t alter internal clocks It s 24 hours no matter what one does External stimuli like an alarm clock can subtly alter our rhythm but only if it s close to 24 hours Mondays stink we tend to be more exhausted on Mondays than any other day On the weekends most of us tend to ignore the external stimuli that keep us to 24 hours we tend to stay up later and sleep later because we can By the time Monday morning rolls around our bodies internal clocks don t match up with external clocks The best thing to do is go to sleep and wake up at the same time It s the same reason that people prefer to fly west than east If one flies west one can stay up later and sleep later flying east really messes one up If one wants to get adjusted to a new schedule one needs about a day for every time zone you cross Studying baseball teams visiting team won 44 time when flying west flying east won only 36 of the time Usually they win about 46 of the time showing a home field advantage Significant jet lag can be incredibly harmful to the brain Neurons die Affects the hippocampus A lot of people work night shifts Night shift work does not reset one s clock One s sleep wake cycle doesn t just reverse Accidents are more prevalent at night than on day shifts Where is the biological clock Researchers did a lot of stuff to try and mess with it before they tried to locate it The clock seemed to be impervious to anything they tried They tried shock food deprivation drugs and lots of different types of brain damage Only one type of brain damage had any effect this was part of the hypothalamus that had the SCN It s located directly above the optic chiasm this sends information directly to the SCN If the nerves for the optic chiasm to the SCN are destroyed light cannot reset the biological clock even if the person can see perfectly fine Conversely if the individual is almost completely blind and the neurons are intact light will reset the biological clock Those pathways send information from specialized ganglion cells in the retina that only respond to light very slowly turning on or off These cells are not responsible for vision because they don t respond to rapidly changing light They have their own special photopigment called melanopsin The SCN produces a couple of different proteins Protein PER is encoded by the gene period And TIM which is encoded by the gene timeless So it produces PER and TIM and these levels increase as the day progresses Once they reach a certain level they interact with another protein called clock that shuts down further production This then decreases levels of PER and TIM to almost nothing and then it starts all over again SCN also regulates release of melatonin from the pineal gland Production of melatonin begins anywhere between 8 and 10 PM Light can affect either PER or TIM and melatonin can prevent that from happening Spontaneous bursts of light can wake one up but melatonin is supposed to stop that from happening The SCN does control the timing of sleep but it doesn t cause sleep Sleep is a behavior it s not the absence of behavior Someone who is sleep deprived for a long period of time will get irritable might have tremors get dizzy might start to hallucinate GAMA builds up get impaired cognition Sleep deprivation is a huge part of any kind of brainwashing because one is not thinking clearly when one is sleep deprived But one does not overall see brain damage from sleep deprivation Stress is the key factor that causes damage to the hippocampus when it comes to sleep deprivation Some people argued that sleep is very similar to hibernation They argued that sleep keeps us out of harm s way If you think about other species it sort of makes sense Prey like cows don t sleep very much they eat a lot but don t sleep a lot Predators like cats sleep a lot But taken to an extreme that means some species shouldn t sleep at all But every single organism sleeps There are species that have ways to get around potential issues Dolphins are able to sleep one hemisphere at the time so right hemisphere is awake left is sleeping soundly More people argue evidence for it that we need sleep because it allows the brain to go through the motions of the day Don t really need sleep as far as physical exertion is concerned But cognitively sleep is needed Real recent evidence indicates that one sees CSF channels expand during sleep allowing more fluid to get to all parts of the brain to wash away extra debris and waste product from the exertions of the day We learn a lot about sleep through the use of an EEG This measures the electrical activity that occurs in the brain Researchers also use a polysomnograph which measures eye movements and gets EEG information Researchers were surprised to find out that sleep came in stages Firstly if one is awake and fairly alert something called beta waves will be happening If one is awake and more relaxed alpha waves will be seen Stage 1 of sleep is a transition stage between sleep and wakefulness Brain activity is pretty synchronized