Sleep Flashcards
circadian rhythms
functions that have a 24 hr rhythm
may be behavioral, physiological, or biochemical- eg. thirst, body temp, hormone levels= all have biological origin
diurnal
active during the light
nocturnal
active during the dark
biological clocks
leads to precise timing
endogenous- not quite 24 hr
entrain- (set) to light-dark cycles
entrain clock
with continuous dim light, behavior becomes free-running
when the light cycle shifts, the behavior also shifts
what allows for entrainment?
light (visual input)
meals
sleep
jobs/class
activity (exercise)
several of these inputs are also regulated by the biological clock
suprachiasmatic nucleus (SCN)
biological clock in SCN in hypothalamus
when SCN is damaged
if light/dark cycle maintained, no change in behavior
if only dim light, random behavior
isolated SCN neurons
can create circadian rhythm via chemical release (encapsulated in plastic)
SCN sequence
happens in a cycle (takes around 24 hrs- per/cry rises in light)
1. clock and cycle bind to form dimer
2. clock/cycle cause per and cry transcription
3. per and cry dimerize
4. per/cry inhibit clock/cycle activity
5. over time, per and cry degrade
6. allow clock and cycle to dimerize
molecular clock based on cyclical levels of :
clock and cycle/Bmal1
per (period) and cry (cryptochrome)
how does light information reach SCN?
retinal ganglion cells (RGC) project to SCN (retinohypothalamic pathway)
retinal ganglion cells (RGC)
RGC do not get information from rod and cone cells
RGC contain melanopsin (sensitive to light, especially blue light)
retinohypothalamic pathway
- light causes glutamate release in SCN
- glutamate increases Per and Cry transcription
- synchronizes SCN neurons to each other and light/dark cycle
classes of sleep
non-REM sleep (NREM)
rapid-eye-movement sleep (REM)
monitoring sleep
electroencephalography (EEG)
electro-oculography (EOG)
electromyography (EMG)
EEG
measures brain waves- brain potentials
synchronized routes of action potentials
EOG
eye movements
EMG
muscle tension
non-REM sleep
has 3 stages and a reduction in postural tension
REM sleep
has small-amplitude & fast EEG waves, no postural tension, and rapid eye movement
stages of sleep
90-110 min
NREM (stages 1-3)
REM
waking
while alert: mix of fast frequencies and low amplitude waves
called beta activity of desynchronized EEG
stage 2
sleep spindles
if waken up during stage 1 or 2, the person may deny they were sleeping
sleep spindles
bursts of activity waves
stage 3
slow waves sleep (SWS) has large-amplitude, very slow waves called delta waves
synchronization of cortical activity
REM
small-amplitude, high-frequency waves
no postural tension
rapid eye movements under eyelids
vivid dreams (vs. thinking)
REM sleep is sometimes called paradoxical sleep
young adult sleep
young adults should sleep 8 hr/night
REM episodes lengthen
stage 3 disappears
approx 2 hr REM/night
cannot fully “repay” sleep debt
Why do we sleep?
energy conservation
niche adaptation
body restoration
memory consolidation
energy conservation
reduced muscle tension, heart rate, blood pressure
niche adaptation
nocturnal vs. diurnal
body restoration
toxin build-up in CSF flows out of brain faster
memory consolidation
sleep helps you retain information
neuronal activity patterns of learning are repeated during stage 3
synaptic remodeling
sleep centers
basal forebrain
reticular formation (wakefulness)
subcoeruleus
basal forebrain
NREM
activity in basal forebrain- turns on non-REM sleep
reticular formation
wakefulness
activated when you have to get up in the night
subcoeruleus
REM sleep
basal forebrain stops being activated and subcoeruleus
paralysis of alpha motor neurons
hypothalamus (4th sleep center)
hypocretin/orexin cells send information to 3 other sleep centers
control switch between awake, NREM, REM (narcolepsy and sleep paralysis)
