Introduction to sleep Flashcards
Whats the OED definiton of sleep?
a condition of body and mind which typically recurs for several hours every night in which the nervous system is inactive, the eyes closed, the postrual muscles relaxed, and conciousness practically suspends
Describe the loss of perception of senses during sleep
-senses continue
-thalamus blocks sensory signals travelling to the cortex where they are normally conciously perceived
What is unihemispheric sleep?
some species have evolved the ability to uncouple the two hemispheres of the brain
What are the four theories of sleep?
-evolutionary
-energy conservation
-restoration
-brain plasticity
Describe the evolutionary theory of sleep
-inactivity at night is an adaption that has a survival function, as animals which stay quiet during vunerable periods and have an advantage over animals remaining active
-reduced accidents when active in the dark
-reduced predation
-conversly there is a reduced ability to react to threat whilst asleep
Describe the energy conservation theory
-the primary function of sleep is to reduce an animals energy demand and expenditure
-provides periods of inactivity
-some animals-hibernation acts as a mean of conserving energy
Describe the restorative theory
-sleep provides and opportunity for the body to repair and rejuvinate
-many major restorative functions such as tissue repair and growth hormone release occur during sleep
describe the restorative theory in more detail
-rate of cells divion and protein synthesis increases during sleep
-NREM sleep is important for restoring physiological functions
-Rem sleep is essential in restoring brain systems
-following sleep deprivation there is an increase in periods of REM sleep
Describe the glymphatic system
-drains toxins from the brain in a similar manner as the lymphatic system
-more active during sleep
-glial cells that are distributed throughgout the brain shrink during NREM sleep to increase space between the neurons, so allowing cerebral spinal fluid to flush out toxins
describe the brain plasticity theory
-sleep is correlated to changes in structure and organisation of brain plasticity
-sleep is critical in the brain development of infants and young children
-sleep deprivation reduced ability to learn and perform tasks
Whats the relationship between sleep and memory?
-sleep favours processes of memory consolidation that cant occur whilst awake due to environmental demands
-sleep deprivation impairs cognitive function
-REM and SNS sleep are the most important in memory consolidation
Describe the EEG
-1982
-elecrtoencephalogram by Hans berger
-electrodes placed on the scalp to record electrical activity of the brain, differences between sleep and awake states recorded
-used to instigate different types of sleep by determining different waveforms
Name the different brain wave types and occurance
infraslow-unknown
delta-sleep
theta-sleep
alpha-awake and resting
beta-awake-cognitive tasks
gamma-awake-peak concentration
List the wave speed in HZ of the different brain wave types
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 two stages of sleep?
-REM
-NREM (non rem)
What are the stages of NREM?
stage 1- transition from wakefullness to sleep
stage 2-first unequivocal stage of sleep
stage 3-slow wave sleep
Describe NREM sleep stage 1
-first 1-10 mins of sleep
-2-5% of sleep
What are some features of NREM sleep stage 1?
-body muscles are functional
-breathing and HR slow down and become regular
-BP and brain temp decrease
-hyponogogic jerk
Describe the EEG changes in NREM stage 1
brain activity slows, transisiton from beta to gamma waves, slower and more synchronized alpha waved when eyes closed and then onto theta waves
Describe NREM sleep stage 2
-last 10-25 mins in the intial cycle of sleep and lengethens with each successive cycle
-45-55% of sleep
List some special features of NREM sleep stage 2
-HR slows
-Body temp drops
-metabolic functions slow to prepare for deep sleep
-harder to wake
Describe the EEG changes during NREM sleep stage 2
-Theta waves form
-sleep spindles-short burst of brain activity of 12-14HZ lasting 0.5s
-K complex occurs every 1-2 mins
-protect sleep, supress outside stimuli and help memotry consolidation and info processing
Describe NREM sleep stage 3
-begins at 35-45 mins of sleep
-spend aprrox 15-20% sleep time here
List some special features of NREM sleep stage 3
-delta sleep
temp,Breathing rate, HR, Bp at lowest levels
-dreaming
-hard to rouse sleeper
-stage where parasomnias occur(sleep talking and walking)
-info proccessing and memory consolidation occur
-children and young adults have more stage 3 sleep than adults
