Introduction to sleep Flashcards
Define sleep
A condition of the body and mind which lasts for several hours each night, occurring cyclically
Where the nervous system is inactive, eyes closed, postural muscles relaxed and consciousness suspended
Define unihemispheric sleep
This occurs to certain mammals that have uncoupled the hemispheres of their brain e.g., dolphins, enabling half their brain to sleep whilst the other hemisphere is active to enable movement in water
(also occurs in birds)
What are the 4 sleep theories?
Evolution, brain plasticity, restoration & energy conservation
Explain evolutionary theory regarding sleep
The inactivity during the night has been proposed to be an adaptation vital for survival. As staying quiet, still-moving & overall inactive proves an advantage of not creating attention that could draw in predators
-reduced predation
-reduced accidents in dark
-reduced exposure to threat
(if sleep wasn’t important animals would have adapted to survive without it)
Explain the energy conservation theory
The theory is that sleep occurs to limit energy expenditure as sleep provides rest and inactivity
This decreases the demand on the body.
e.g., hibernation in bears
Explain the brain plasticity theory
This theory suggests that there is a correlation between brain structure & organization of the brain regarding to sleep
Sleep is seen as essential for the brains ability to perform tasks & to learn.
Explain the restoration theory
This theory suggests we sleep in order to undergo growth, repair & restoration.
We are more likely to deal with illness & injury when sleep-deprived.
Sleep deprivation causes a reduction in immune efficiency
Tissue growth & repair occur during sleep, rate of protein synthesis & cell division increase during sleep
The hormone of HGH is released during NREM sleep
Define NREM
Known as non-eye rapid movement sleep, which is required for restoration of physical function, HGH released during NREM
Define REM
Known as rapid eye movement sleep, which is needed to restore brain function, there is an increase in REM sleep during sleep deprivation. Brain repair cannot occur when conscious
How is sleep measured?
Measured by an EEG, involves electrodes placed on the scalp to measure different types of waves & record the electrical activity of the brain. This is used to identify sleep stages, patterns & abnormalities
What is the function of the glymphatic system
This system drains toxins from the brain, similar to the lymphatic system, however, this system is 10-20 more times active during sleep
Glial cells found in the brain shrink allowing large gaps between neurons, enabling cerebral fluid to flush out toxins
What is the effect of sleep on memory?
It is known sleep deprivation affects cognitive function
Memory consolidation (STM->LTM) cannot occur whilst awake due to environmental demands
REM is very important for memory consolidation, found slow wave sleep & REM are vital
What are the types of sleep waves & how are they measured?
Waves are measured by amplitude, frequency & wavelength
(1Hz=1 wave/s)
infraslow=<0.5
Delta=0.5-3.0
Theta=3.0-8.0
Alpha=8.0-12.0
Beta=12.0-38.0
Gamma=38.0-42.0
What are the 3 stages of NREM sleep?
- transition from wakefulness to sleep
- first sleep stage
- slow wave sleep (SWS)
Describe events occurring in S1 of NREM
Occurs in first 10 minutes, 2-5% of time spent in this stage
- body muscles are still functioning, eye-rolling occurs, waking in this stage makes us feel we have not slept at all
-HR & BR begins to slow, BP & temperature decreases,
-hypnogogic jerk (falling sensation)
