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Questions and Answers
What differentiates the sleep cycles of birds from those of mammals?
What differentiates the sleep cycles of birds from those of mammals?
What is characteristic of unihemispheric sleep in birds?
What is characteristic of unihemispheric sleep in birds?
Which statement about sleep in reptiles, amphibians, and fish is true?
Which statement about sleep in reptiles, amphibians, and fish is true?
What key element indicates that REM sleep evolved separately in birds and mammals?
What key element indicates that REM sleep evolved separately in birds and mammals?
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How do birds and mammals differ from reptiles in terms of thermoregulation during sleep?
How do birds and mammals differ from reptiles in terms of thermoregulation during sleep?
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What sleeping pattern is characteristic of the !Kung culture?
What sleeping pattern is characteristic of the !Kung culture?
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What was commonly observed in pre-industrial hunter-gatherer tribes regarding napping?
What was commonly observed in pre-industrial hunter-gatherer tribes regarding napping?
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What evidence suggests that there is a biological basis for a dip in alertness during the day among humans?
What evidence suggests that there is a biological basis for a dip in alertness during the day among humans?
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Study Notes
Insect Sleep
- Sleep cannot be tracked in insects
- The behavior of insects can give insights into sleep, which is a term that cannot be used for insects
- Dr. E. Rhoschild researched the following insect characteristics:
- Circadian Timing: awake during the day, not at night
- Horizontal position:
- Low muscle tone:
- Non-response (but reversible):
Bird Sleep
- Birds display physiologically confirmed cycles of NREM and REM sleep.
- NREM sleep episodes are around 2.5 minutes in length.
- REM sleep episodes are around 8 seconds long.
- Birds do not have total muscle tone loss during REM sleep as mammals do.
- Birds have unihemispheric sleep, where one half of the brain sleeps at a time.
- Only happens during NREM sleep (though both sides can be in NREM simultaneously.)
- Both halves of the brain sleep during REM, there is no unihemispheric REM.
- Possible states of bird sleep:
- Awake/Awake
- Awake/NREM
- NREM/NREM
- REM/REM
- NREM/REM (unique to birds)
- The White-crowned sparrow is being researched to see if there is a way to skip sleep.
- NREM sleep episodes are around 2.5 minutes in length.
- Birds with one brain hemisphere in SWS will keep their eye open on that side, but the other eye will be closed.
Amphibian, Fish, and Reptile Sleep
- It is difficult to track sleep in these animals.
- While amphibians, fish, and reptiles have brain activity indicative of NREM sleep, it is not the same as that seen in mammals and birds.
- Many studies failed to find REM sleep in amphibians and fish.
- Researchers argue there may be REM-like activity in reptiles, but this remains debated.
Evolution of Sleep
- Birds and mammals (who have REM sleep) evolved separately from reptiles
- REM sleep evolved twice: once in birds and once in mammals.
- NREM sleep is the original stage of sleep, with REM evolving later.
Clues to Sleep Function
- Thermoregulation: Birds and mammals regulate body temperatures differently than reptiles.
- Metabolic regulation: Birds and mammals increase their metabolic rate to maintain a constant body temperature in cold temperatures. Reptiles cannot do this.
Human Sleep
- The !Kung of Africa sleep on the ground or hard pallets.
- They do not use pillows.
- They sleep collectively.
- They use minimal bedding to avoid insects.
- They frequently nap, especially during dry, hot seasons
- Most pre-industrial hunter-gatherer tribes nap for 30-60 minutes during the afternoon.
- Humans are biologically programmed to have a dip in alertness mid-day.
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