Introduction to 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

-senses continue -thalamus blocks sensory signals travelling to the cortex where they are normally conciously perceived

some species have evolved the ability to uncouple the two hemispheres of the brain

-evolutionary -energy conservation -restoration -brain plasticity

-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

-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

-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

-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

-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

-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

-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

-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

infraslow-unknown delta-sleep theta-sleep alpha-awake and resting beta-awake-cognitive tasks gamma-awake-peak concentration

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

-REM -NREM (non rem)

stage 1- transition from wakefullness to sleep stage 2-first unequivocal stage of sleep stage 3-slow wave sleep

-first 1-10 mins of sleep -2-5% of sleep

-body muscles are functional -breathing and HR slow down and become regular -BP and brain temp decrease -hyponogogic jerk

brain activity slows, transisiton from beta to gamma waves, slower and more synchronized alpha waved when eyes closed and then onto theta waves

-last 10-25 mins in the intial cycle of sleep and lengethens with each successive cycle -45-55% of sleep

-HR slows -Body temp drops -metabolic functions slow to prepare for deep sleep -harder to wake

-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

-begins at 35-45 mins of sleep -spend aprrox 15-20% sleep time here

-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