Sleep Flashcards
sleep pressure (sleep debt)
the cumulative loss of sleep and the consequent pressure for sleep that results in an inadequate amount of physiologically normal sleep
- happens bc sleep-wake behaviour is under homeostatic control
how does sleep pressure change over 48 hours?
- over the time that we spend sleeping, our sleep pressure decreases
- once we wake, our sleep pressure begins to build again, causing us to feel sleepy until we go to sleep again
what happens to sleep pressure when you skip a night of sleep?
the pressure to sleep continues to build until you finally sleep
what happens to sleep pressure if you take a nap during the day?
some sleep pressure would be releived and the pressure would build again after that
- depends on length of nap
describe 3 examples of how sleep pressure can interfere with human performance
- driving sleepy (>16h w/o sleep) = driving legally intoxicated
- impairs motor control, reaction time, our ability to assess situations
ex. truck drives, airline pilots, medical professionals (shift work)
how much sleep is recommended for:
children (6-13)?
teens (14-17)?
adults (18-64)?
children: 10-11
teens: 8.5-9.5
adults: 7-9
how to calculate sleep deficit (deprivation)
= amount of sleep we need - amount of sleep we get
limitations of calculating sleep deficit with equation provided in class
- it doesn’t take into account the way we sleep (ie. sleep quality, or time spent in bed but not asleep)
sleep latency
the time between when we go to be and when we actually fall asleep
mid-sleep disturbances
the time when we wake up mid-sleep for awhile before falling back asleep
how do sleep latency and mid sleep disturbances interfere with sleep quality?
it affects our sleep efficiency
sleep efficiency = sleep time/time in bed which will be less than 100% if we have large latencies/disturbances in our sleep
sleep fragmentation
having multiple mid-sleep disturbances over the course of a night
ex. having sleep apnea, you stop breathing while you sleep so your body wakes you up multiple times a night to get breathing again resulting in multiple sleep disturbances
- individuals often feel sleepy throughout the day
sleep efficiency
= sleep time/time in bed
- we want to have as close to 100% as possible
how does sleep pressure differ for an individual who is rested vs drowsy?
- pressure to sleep will be less for someone who is rested than for someone who is drowsy
describe the details of the study that demonstrated the correlation b/w poor sleep quality and academic performance
assessed the sleep quality of 400 university students and related it to their academic performance
- found that those with low sleep quality did much poorer academically than those with high sleep quality in all of their courses
- shows that sleeping helps us perform better academically
what factors should we account for when calculating the costs associated with sleep deprivation?
- lost productivity and human error due to decreased attentiveness, focus and memory
- heath care costs associated with physical and mental health disorders
- chronic sleep disturbances increase mortality and morbidity and can lead to premature death
what physiological changes occur from sleep to wake?
during sleep:
- body temp regulated about 1 degree lower
- muscle tone similar to wakefulness
- respiratory rate decreases, becomes more regular
- HR and BP decrease
- brain activity changes
what is an excitatory postsynaptic potential?
- the input into a postsynaptic cell that will cause an AP (cell output)
- they add up to produce a threshold depolarization
steps for depolarization
- AP reaches axon terminal of presynaptic cell, depolarizes the membrane
- voltage gated Ca2+ channels open and Ca2+ flows in
- synaptic vesicles releases neurotransmitter into synaptic cleft
- NT binds to receptors on target cell, usually causing +ve ions to flow in and depolarize the next cell and cause an AP
EEG
what does EEG measure?
EEG = electroencephalogram
- measures brain activity (specifically EPSPs)
which 2 things are necessary for EEG to record brain activity?
optimal conditions:
- synchronous activation of populations of neurons
- neurons must be aligned to create a dipole that can be measured by electrode on scalp (parallel to one another, perpendicular to surface) to help create summation
EOG
what does it measure?
electro oculogram
- measures electrical activity around the eyes
EMG
what does it measure?
electro magnograph
- measures electrical activity in our muscles while seated, at rest
what does frequency measure?
the rate of cycling of EEG waves
- measured in Hz (cycles per second)
what are the different EEG frequency bands?
- beta
- alpha
- theta
- delta
beta wave frequency
14-30 Hz
- represent mental activity while awake
alpha wave frequency
8-13 Hz
- represent mental activity while awake resting
theta wave frequency
4-7 Hz
- represent mental activity while asleep
delta wave frequency
< 3.5 Hz
- mental activity during deep sleep
how do the EEG recordings differ for awake and NREM sleep?
what frequencies are most dominant?
wake: beta and alpha waves observed
- fast, low amplitude waves that are desynchronized
sleep: theta and delta waves
- slow, high amplitude waves that are desynchronized
amplitude
the number of cells that are synchronized
- the more synchronized cells, the higher the amplitude of the signal
why is the amplitude of the EEG signal larger during NREM than during wake?
because the waves are slower in NREM, and when the frequency of cycles decrease, the amplitude of the waves get larger representing that there are more cells that are synchronized
what is the ascending activating system (AAS) and what brain regions are involved?
signals travel through the reticular formation, medulla, pons and sends EPSPs to the thalamus which activates the cerebral cortex, waking us up
- AAS is activated by vision, sounds, touch, and movement stimuli
reticular formation
a collection of nuclei in the brain centre that is a part of the brainstem where ascending general sensory info travels through to the rest of the AAS
- activation of reticular formation is critical for switching brain waves from synchronized (sleep) to desynchronized (wake)
how does the sound of your alarm clock have an impact on the activity of the reticular formation and cortex?
it travels through the AAS, to the thalamus which relays the info to wake up the cortex
what would happen if the reticular formation were damaged?
we may become comatose - unresponsive and unconscious (not desynchronized by afferent - aka incoming - stimuli)
- also observed: slow, high amplitude EEG
what would happen if the reticular formation were always activated?
we wouldn’t be able to fall back asleep ?