Sleep Flashcards
Sleep-wake behaviour is under_
homeostatic control
def sleep debt
The cumulative loss of sleep and the consequent pressure for sleep that results from an inadequate amount of physiologically normal sleep.
Sleep debt is cumulative - what does this mean?
- sleep pressure adds up - sleeping pays it off
- at some point, the brain will not allow you to stay awake even under dangerous circumstances (ex. driving)
How many hours of sleep deprivation are equivalent to being intoxicated?
> 16 hours of sleep
What relationship is noticed between shift length and accident rate?
Accident rate increases by a lot
(ex. errors made by medical students working 29 hr shift> errors made by students on 2 15 and 14 hour shifts
*(Landrigan et al, 2004)
def microsleeping
when the brain transitions to deep sleep for mere seconds
What accumulates in your brain when you’re awake?
metabolic waste
How much sleep do children 6-13 yrs old need?
9-11 hrs
How much sleep do teens 14-17 yrs old need?
8-10 hrs
How much sleep do adults 18-64 yrs old need?
7-9 hrs
How much sleep do adults +65 yrs old need?
7-8 hrs
What’s the average sleep deficit per person and in total per year in Canada?
- 1.1 hours per person
- 14 billion hours per year
What 2 categories influencing/affecting disparities in sleep duration were noticed in American children? (Giggens et al 2022)
- race/ethnicity
- income
Eqn for sleep efficiency
sleep time/time spent in bed
What sleep efficiency is normal?
80-90%+
def sleep latency
the time between lying in bed and sleeping
What 2 factors are not counted when looking at time spent asleep?
sleep latency & mid-sleep disturbance/ sleep fragmentation
Acute sleep deprivation impairs _
vigilance and cognition to increase human errors
What’s the association between poor sleep quality and academic performance?
higher GPA in those with high sleep quality
Name negative 4 factors associated with chronic sleep disturbances:
- Obesity
- Heart Disease
- Weakens the Immune System
- Mental Illness
What are 4 physiological changes that happen when asleep?
- HR and BP decrease
- brain activity changes
- respiratory rate decreases and becomes more regular
- body temperature is regulated at a lower set point
EPSPs add up to produce threshold depolarization - describe how depolarization works
- Action Potential reaches axon terminal and depolarized membrane
- Voltage-gated Ca2+ channels open and Ca2+ flows in
- Ca2+ influx triggers synaptic vesicles to release neurotransmitter
- Neurotransmitter binds to receptors on target cell, causing ions to flow in
What type of brain imagery can reflect the summation of simultaneous EPSPs?
EEG
- electrode placed on skull with electical conductor gel can detect mv changes in electrical activity
Can you see EPSP signals through an EEG?
Yes! Due to the layered orderly structure of the neocortex, if many EPSPs are occuring simultaneously, the signal is strong enough to be read with electrodes placed on the surface of the head
*neurons need to be in same alignment though
EEG reveals _
the pattern of electrical activity from large population of neurons
EEG records _ through time like a polygraph
electrical events as deviations
What general pattern of brain wave activity is noticed in wake vs sleep?
Wake
- fast, low amplitude waves that are desynchronized (“buzz/chatter”)
Sleep
- slow, high amplitude waves that are synchronized (neurons fire together)
Which part of the brain “wakes” up the cortex?
The ascending activating system (AAS)
Describe the location of the AAS and how it works when waking you up
- runs along the entire length of the brain stem
- AAS is activated by a series of stimuli
- runs through medulla and pons and sends a signal to the thalamus
- the thalamus “relay station” communicates the message to the whole cortex
List external sensory stimuli that can activate the AAS
- auditory impulses (ie. alarm clock)
- morning sunlight
- splashing water on your face
- exercise/movement
How was the AAS’s function discovered?
by electrically stimulating the AAS and comparing the EEG to an EEG showing sleep-wake wave changes
Damage to what area causes the unresponsiveness and unconsciousness observed in a coma?
the AAS (no deviations in EEG trace from external stimuli)
Which 3 brain areas in the brain stem are associated with a more alert brain and which neurotransmitter do they release?
- LC/Locus Coeruleus (norepinephrine)
- Raphe/dorsal and median raphe nuclei (serotonin)
- TMN/tuberomamillary nucleus (histamine)
*all inhibit VLPO while awake
When awake, the AAS inhibits _ (area in brain stem)
the VLPO (ventrolateral preoptic area)
What other structure inhibits the VLPO and acts as a “backup system”?
LHA (lateral hypothalmic area), releases orexin
A deficiency of what neurotransmitter is associated with narcolepsy?
orexin
When you need to sleep, the _ (brain area) releases _ and inhibits _ (brain areas)
VLPO releases GABA and inhibits the LC, Raphe, TMN, and LHA
Damage to which brain area can be associated with insomnia?
VLPO (ventrolateral preoptic area)
What process is referred to as a sleep-wake “switch”?
The mutual inhibition of the arousal promoting and sleep promoting brain areas
What happens to the thalamus, AAS, and pattern of APs when you’re asleep?
- thalamus put in burst mode (causes brain to synchronize and sleep)
- AAS is off
- bursts of APs spaced out
What happens to the thalamus, AAS, and pattern of APs when you’re awake?
- Thalamus put in spike mode (causes activation & desynchronization of the cortex)
- AAS ON
- single APs one after the other
What 2 factors cause sleepiness? (what “flips” the sleep-wake switch)
- biological clock
- homeostatic factor (sleep pressure)
Describe the biological clock
- housed in the SCN (superchiasmatic nucleus)
- has clock genes that transcribe proteins in a 24.2 hr cycle, creates a biological rhythm
- since it is not exactly a 24 hr cycle, we need environment cues to resynch schedule (Zeitgebers)
Describe zeitgebers
- “time-givers”
- resets clock to 24 hours
- sunlight is the strongest zeitgeber by triggering the cycling of melatonin (body’s natural sleeping aid)
- Exercise isn’t as good as sunlight for resetting, but when combined they have a compounded effect
Sleep pressure is caused by the buildup of _
Adenosine
- byproduct of ATP
- inhibits AAS when too high
How does caffeine affect sleepiness?
blocks adenosine from binding to it’s receptors, inhibiting sleep pressure
Describe stage 1 of sleep
- drowsy, transition state
- only a couple minutes
- rhythms start to synchronize more, not sleeping yet
Describe stage 2 of sleep
- consciousness starting to fade
- brain getting more synchronized aside from occasional bursts of activity (sleep spindles & K complex
- function of sleep spindles and K complex unclear but seem to help deepen sleep
- brain consuming energy, recharging a little
- spend 10-25 mins here
Name and describe the deepest stage of sleep
Slow wave sleep
- most synchronized stage of sleep
- completely unconscious
- dominated by big delta waves (polarity creates a rhythm in CSF that washes the brain clean from metabolic waste)
- slow enough that you don’t expend much energy and pay back sleep debt
- 20-40 mins
In which stage of sleep do you pay off the most sleep debt?
Slow wave sleep
Describe REM(rapid eye movement) sleep
- paradoxical stage of sleep
- brain wakes up, desynchronized
- eyes rapidly dart around
- can’t move muscles, “Atonia”
- the stage where we have the most vivid/emotional dreams
- does not take away from sleep debt
- spend only a few mins here at a time
Describe the cycles of sleep
go from awake>stage 1>stage 2>slow wave sleep>stage 2> REM
- as sleep gets longer, spent less time in SWS (none in cycle 5) and more in REM
Why do a lot of people wake up in the middle of the night?
corresponds with the time you are in REM sleep, see a spike in awakeness in cycle 4
how long does each cycle last?
90 minutes
What’s a healthy distribution of time, in percentages, in each stage of sleep for young adults?
REM 25%
SWS 20%
Stage 2 50%
Stage 1 5%
What happens to SWS starting in adolescence? What is a possible health concequence?
time spent in SWS starts to decline
Young adults (20%)
Older Adults (5%) *linked to alzheimers due to inability to clear amyloid plaque
What happens to SWS delta power through the night?
progressively declines (smaller intensity waves)
How does sleep deprivation affect the time spent in total sleep and SWS?
- time spent in SWS and total sleep time % increases
- delta waves increase to pay back sleep debt faster
(older adults don’t always produce enough delta waves to go into SWS for long enough so this doesn’t always happen for them)
Based on a study by Werth el al., 1996, what happens to time spent in SWS, sleep latency, and delta waves after early evening naps?
Time spent in SWS decreases, sleep latency increases, and delta wave amplitude decreases (sleep debt payed off in part during nap)
In a study (Rupp et al 2009) ran on regular vs restricted sleep effects on time spent in SWS, what was found?
Regular sleep (480 min) had 90 mins of SWS
Restricted sleep (180 min) had 80 mins of SWS (body prioritizes it)
What cannot be produced in fatal familial insomnia?
- sleep spindles cannot be produced, stays in stage 2 and can’t sleep deeply
- causes neural degeneration of the thalamus
People are more likely to recall dreaming when woken up during _ than _
REM sleep, Non-REM sleep (SWS)
* (Aserinsly & Kleitman, 1953)
Why is REM sleep very important?
- helps reorganize neural circuits that were active during the day
- decreases the emotional distress caused by memories (calms amygdala down & makes distressing events seem less distressing)
- the longer you stay in sleep, the less active the amygdala is (Wassing et al., 2019)
What effects does alcohol have on sleep?
- promotes deep sleep at very beginning of night
- severely disrupts REM sleep
*could cause heightened anxiety/emotional distruption
What effects does canabis have on sleep?
- distrupts REM sleep, especially strands with lots of THC *could cause heightened anxiety/emotional distruption
