neurobiology of sleep Flashcards
what defines sleep stages?
brain activity, muscle activity, and eye movements
what are the two main processes that regulate sleep?
circadian and homeostatic processes
what is homeostatic pressure
‘sleep debt’ - how tired you feel
what is circadian rhythm
entrained 24hr rhythm of sleepiness and wakefulness
what is ultradian rhythm
cycle of less than 24hrs - shorter sleep cycles of changes that occur within the circadian rhythm and nrem and rem cycles - changes in sleep depth, awakening, etc
what is some evidence that slow wave sleep is one of the most important processes for being fully rested?
-babies and kids have more slow wave sleep
-slow wave sleep is more concentrated early on in the night (when we first go to bed and are tired)
- when we are kept awake for a long time and finally allowed to sleep, we go straight into slow wave sleep
why do we say that a lot of the arousal systems in the brain are ‘redundant?’
because we have so many of them - waking up from sleep is so important that we need many systems so that if one is damaged, another can compensate for it
why do we say that arousal systems are global
because arousal systems are networks involving many brain areas and neurotransmitters
- neurons with long axons, descending and ascending projections
why is REM sleep unique in terms of arousal?
because some arousal systems are off and others are off
- we have cortical arousal in REM but muscle atonia
why is the arousal system ascending
because it starts in the brainstem and goes all the cortex
upper brainstem → posterior and lateral hypothalamus → basal forebrain
orexin
neurotransmitter that particularly affects motor arousal - very important for REM sleep regulation. Orexin projections go to the forebrain and the brainstem.
what happens when you have a lack of orexin?
lack of orexin is associated with narcolepsy with cataplexy
condition where patients spontaneously enter REM sleep and lose muscle tonus during the day - sometimes happens when experiencing strong emotion
which neurotransmitters are involved in wake -on, rem-off arousal?
- serotonin
- norepinphrine (high discharge in wake and low in nrem, off in rem)
- histamine (high in wake, low in nrem, off in rem)
- orexin
which neurotransmitters are involved in wake -on, rem-on arousal
neurotransmitters that are high in waking and high in rem (but low in nrem)
- acetylcholine
-dopamine
-glutamate
which area of the brain regulates sleep?
the ventrolateral preoptic areas in the hypothalamus (just next to the optic chiasm)
- contains sleep promoting neurons - more active in sleep (nrem and rem(
- responsive to sleep deprivation and accumulation of homeostatic pressure
- some regulating stuff is also in the median preoptic nucleus
what is the main neurotransmitter in the ventrolateral preoptic area?
GABA (also the most important inhibitory neurotransmitter in the entire brain)
- inhibits wake promoting arousal circuits and is associated with sleep promoting circuits
what is the flip flop sleep switch system?
describes the coordination between sleep and wake systems
both systems are always acting to inhibit each other, however, which one wins out depends on homeostatic pressure and circadian rhythms
for example:
in wake, the vlpo is inhibited by arousal systems. however, in sleep, vlpo inhibits arousal systems.
when is orexin most positively expressed? when is it expressed the least
expressed the most:
- positive emotion
-social interaction
- negative emotion
expressed the least:
- awake while in pain
- sleeping just before wake
-sleeping
- after eating
- before eating
- sleep onset
what is the difference between tonic and rhythmic patterns?
tonic = desynchronized
rhythmic: synchronized
what are thalamocortical loops?
connections between the thalamus and the neocortex - in waking, the thalamus acts as a relay system sending info to the cortex, which is responsible for higher cognitive functions
what do thalamocortical loops do in nrem sleep and rem sleep?
nrem: reduced activity
rem: activity similar to waking
describe how thalamocortical loops play a role in sleep
- they have reduced activity in nrem, allowing us to maintain deep sleep
- they have increased activity in rem, allowing us to dream vividly
- they also play a role in transitioning between sleep and wake
why is it difficult to answer the question ‘what controls sleep?’
because different systems control different parts of sleep and on different scales:
- circadian system
-homeostatic system
-hormonal system
-limbic system
- neocortex
what is adenosine
an inhibitory neuromodulator of the central nervous system - having a bunch of adenosine in our system makes us sleepy
- blocked by caffeine
- inhibits wake promoting neurotransmitters (serotonin, acetylcholine, norepinephrine)
-accumulates in basal forebrain with sleep debt and diminishes during sleep
what is a coffee nap
idea that we can enhance the rejuvenating effects of a nap by timing it with coffee consumption (remember coffee doesn’t work right away!)A
