Sleep and Biological Rhythms Flashcards
How is sleep defined? (simple)
A normal absence of consciousness
What does Siegel’s definition of sleep include? (3)
Rapidly reversible
Reduced sensory responsiveness
Homeostatically regulated - lost sleep increases drive for ‘sleep rebound’
Reasons for sleep? (4)
Energy conservation
Growth and repair
Metabolic clearance
Learning and memory
How does sleep vary across organisms/time?
Need decreases with age
Larger organisms tend to sleep for longer
Smaller sleep in bouts
Patterns change e.g. newborns also may sleep in bouts
Ecological influences of sleep? (4)
Predation risk suppresses
Thermoregulation suppresses
Foraging for food suppresses
Swimming suppresses e.g. dolphins 1/2 a brain at a time to breath at the surface
Intrinsic influences on sleep? (3)
Memory consolidation increases
Energy conservation
Metabolic clearance (byproducts accumulate in wakefulness)
Sleep stages?
Awake
Stage 1, 2, 3, 4
REM
Brain waves of each sleep stage?
Awake - alpha, beta (=alertness) 1 - theta 2 - sleep spindles form, slow waves 3, 4 - slow waves, delta activity REM - theta and beta (resembles awake)
Sleep cycles?
Around 5 per night, with deep sleep (stage 4) only in first 2.
Around 90 minutes in humans
Homeostasis in sleep?
Cycle with homeostatic sleep pressure and internal circadian clock -internal clock pushes past need to sleep until homeostasis kicks in in the evening
Neural systems of sleep? (2)
Forebrain systems - support SWS
Brainstem - activates forebrain for waking, triggers REM
What is the ascending arousal system?
Neural system in rats to govern sleep
Role of orexin?
In sleep - peptide secreted by neurons in lateral hypothalamus and stimulates feeding, related to wakefulness.
Orexin knockouts destroy bout-sleeping in rats and cause narcolepsy like symptoms
Symptoms of orexin knockouts? (4)
Narcolepsy-like; Sleep attacks in the day Cataplexy (weakness after strong emotion) Sleep paralysis Hypnagogic hallucinations
What is unihemispheric sleep (USWS) and where is it found?
Sleeping with on side of the brain - seen in aquatic mammals and fish
Unihemispheric sleep in ducks?
Sleep with one eye open, brain hemisphere on opposite side awake.
Used where there is high predation risk, and often seen depending on location in group i.e. outer edges
USWS in frigate birds?
Large, making long flight trips up to 3000km over water
When flying, they spiral up thermals and glide straight down - USWS associated with the spiralling up, where the same brain side as direction of turn sleeps so they can still see other birds to avoid them.
Sleep in reptiles?
More rapid REM/NREM cycle than mammals/birds - 80s in Australian dragon, but same pattern as us
Zimmerman’s properties of sleep? (4)
Why do we need them?
In simpler nervous systems, we cannot use EEGs.
- Quiescence with species specific posture
- Increased arousal threshold
- Quick reversibility
- Homeostasis i.e. interruption leads to greater need
Measuring sleep in flies?
Test tube - food and cotton at opposite ends with infrared sensor detecting crossing frequency.
Overall conclusions about sleep across taxonomic ranks?
Very similar features - e.g. neurochemicals (exception of orexin, not in flies), patterns and overall properties
Certain features species-specific e.g. cycle length and side of brain
Two mechanisms of biological rhythm control?
Passive/retroactive - relies on homeostasis adapting to changes
Proactively - biological timekeepers
Examples of circadian rhythms? (7)
Body temp Hormone secretion Locomotion Sleep Alertness/cognition Muscle strength Immune function
What is voluntary activity?
Our main source of study for bio rhythms - behaviours that the animals would do anyway, e.g. hamsters running on a wheel
