Lecture 13 Flashcards
circannual cycle
Yearly
- hibernation, fat metabolism
infradian
longer than a day - shorter than a year
- menstrual cycle
circadian
daily
- sleep-wake cycle
ultradian
shorter than a day
- eating
endogenous rhythsm
are driven internally from within the body (biological clock)
exogenous rhythms
are driven externally
e.g., by the sun or the seasons
zeigerbers
environmental events
- periodical synchronisation to environmental events that provide a clock setting cue keeps our biological clock on the 24h cycle
- only able to entrain the circadian rhythm if they occur at the same time each day
what is the most important biological clock structure
suprachiasmatic nucleus
suprachiasmatic nucleus
- part of the hypothal
- located just above the optic chiasm
- receives input from photosensitive retinal ganglion cells via the retinohypothalamic tract
- core neurons are not rhythmic; they entrain shell neurons which are genetically programmed for rhythmicity
nonphotic events
are signaled to the SCN by the intergeniculate leaflet (lateral thalamus) and Raphe nuclei
pace maker - SCN
SCN acts as a biological master clock
- it contains pacemaker cells that have an endogenous rhythm
pacemaker - slave oscillators
these pacemaker cells entrain slave oscillators; other brain structures with circadian rhythmic activity
circadian rhythmic activity at night
pineal gland > melatonin
- melatonin activates the parasympathetic rest-and-digest system
circadian rhythmic activity during the day
pituitary gland > adrenal glands > cortisol
- cortisol supports arousal activities in the sympathetic system
sleep recording techniques (3)
- brain activity (EEG)
- muscle activity (EMG)
- eye movement (EOG)
hypnogram
- first ahlve of the typical night is mainly characterised by NREM sleep, second half REM sleep
- NREM-REM = 90 mins, 5 times a night
REM rebound
if you do not sleep long enough one night, the REM sleep occurs at the beginning of the the following night
activation synthesis theory
dreams are an epiphenomenon of random brain activity
coping theory
dreams are biologically adaptive and lead to enhanced coping strategies for threatening life events
continuation theory
we are problem solvers while awake, and this continues during sleep
the basic rest-activity cycle (BRAC)
activity and rest are organised in time blocks of 90 mins
- rem sleep also occurs (evidence for continuation theory)
sleep as a biological adaption process
- animals sleep to save energy
- diurnal animals sleep to avoid bumping into objects at night
- predators typically sleep more than prey animals
sleep as a restorative process
body recovery: growth hormone during sleep
brain recovery: resting state and cleaning up
sleep and explicit memory storage
in animals: explicit memory traces in the hippocampus are consolidated during NREM sleep
in humans: consolidation of implicit memory occurs during REM sleep
reticular activating system (RAS)
- main brain area responsible for sleeping-waking behaviour
- in brainstem
- stimulation of RAS stimulates the (hypo)thal and cortex and produces an awake EEG patter
- inhibition produces a sleep EEG patter
damage to RAS
results in coma
ventrolateral preoptic nucleus (VLPO)
in the hypothal contains a sleep-wake switch
- brainstem contains a NREM-REM switch
- the switch of off when awake, RAS is active
- switch is on during sleep, inhibits the RAS
NREM sleep disorders
insomnia
hypersomnia - difficulty waking up or staying awake due to prolonged NREM sleep
REM sleep disorders
narcolepsy
sleep paralysis
cataplexy - sudden loss of muscle tone triggered by arousal
