14.2 Why do we sleep, and why do we sleep when we do? Flashcards
what are the two leading theories of why we sleep
recuperation and adaptation
explain recuperation theories of sleep
being awake disrupts the homeostasis of the body in some way, and sleep restores it - differ in terms of what homeostasis is altered
- imply that sleepiness is triggered by a deviation from homeostasis caused by wakefulness, sleep is terminated by a return to homeostasis
what are the two most common recuperation theories
- sleep restores energy levels that decline during wakefulness
- clear toxins, such as beta amyloid from the brain and bodily tissues
explain adaptation theories of sleep
sleep is not a. reaction to disruptive effects of being awake, but the result of an internal 24-hour timing mechanism - humans are programmed to sleep at night regardless of the events in the day
what do adaptation theories focus on
- what is the most radical extension of this position
when we sleep, rather than the function fo sleep
- sleep plays no role in efficient physiological body functioning
what is the cause of the sleep timing mechanism in humans from an evolutionary perspective (according to adaptation theories?
early humans - enough time during the day to get the essential stuff done
- motivation to sleep evolved to conserve their energy resources and make them less susceptible to mishap during the dark
what do adaptation theories compare sleep to?
reproductive behaviour.- highly motivated to engage in it, but dont need it to remain healthy
Do other species sleep?
Is it similar to our sleep?
Yes, most mammals and birds do
yes, high amplitude, low frequency EEG waves punctuated by periods of low amplitude, high frequency waves
is there evidence for sleep in amphibians, reptiles and fish/
sort of, there is periods of inactivity./unresponsiveness, but these periods are not necc related to mammalian sleep
what does the fact that mammals and birds sleep suggest?
- what are the 2 primary pieces of evidence for this?
sleep serves some physiological function, rather than protecting animals from mishap, as
- even species who are at an increased risk of death during sleep still do so
- some species have evolved very complex mechanisms to allow them to sleep, like dolphins who sleep with only half their brains at a time so they can resurface for air
- goes against the logic of nat selection to evolve complex mechanisms for sleep unless it was necc.
what does the fact that mammals and birds sleep suggest in terms fo the nature of sleeps function?
that it is not some special, higher order human function that sleep helps
- ex sleep reprograms complex brains or permits emotional release to maintain mental health are improbable
what doest he large species-differences in sleep time suggest?
sleep may be essential for survival, but not necessary in large wquantities - horses for example get by on 2 to 3 hours of sleep
- sleep patterns of mammals and birds vary between nat env and captivity - increase a lot in captivity
what have studies on why certain species sleep more than others discovered?
- examples
focus non energy related factors - no strong relationship between a species sleep time and level of activity, body size, or body temp
- giant sloth - sleep 20 hours but dont expend a lot of energy
- energy expenditure has little effect on sleep in humans
what do adaptation theories correctly predict about species time spent sleeping
daily sleep time s related to how vulnerable a species is when asleep and how much time it needs to spend each day feeding etc.
- ex - zebras must graze almost constantly to get enough food, and extremely vulnerable to predators while sleeping, so they sleep ab 2 hours/night
- lions often sleep continuously for like 2 to 3 days after a large meal
