8.2.2 Sleep Flashcards
What is the function of sleep?
Energy conservation and repair
Memory consolidation
Clearance of extracellular debris
What are the cycles of sleep?
Awake
Eyes closed
Stage 1
Stage 2/3
Stage 4
REM sleep
How many sleep stages are there?
4 major stages + REM
How are stages characterised?
Typical EEG patterns
Outline the awake with eyes open phase
Beta waves- irregular
50Hz
Outline the awake with eyes closed phase
Alpha waves- regular
10Hz
Outline the stage 1 sleep phase
Alpha + interspersed theta waves - regular
10Hz and 5Hz for theta
Outline the stage 2/3 phase
Theta + interspersed sleep spindles and K-complexes
Sleep spindles- high frequency bursts of activity from thalamus
K- complexes- large spikes, emergence of the intrinsic rate of the cortex
Outline stage 4 sleep phase
Delta waves- regular
1Hz
Related to K-complexes seen in stages 2/3
Outline REM sleep
EEG similar to beta waves
Dreaming mainly occurs in this stage, so EEG is similar to concious patient
Dealing with the sensory input from the brain
What is the neural mechanism of non-REM sleep?
Complex
Deactivation of reticular activating system, cortex and inhibition of thalamus
Deactivation facilitated by removal of sensory inputs
What is the neural mechanism of REM sleep?
Initiated by neurones in the pons
Similar EEG to when awake with eyes open, difficult to rouse due to potent thalamic inhibition
Decreased muscle tone due to glycinergic inhibiton of lower motor neurones
Autonomic functions e.g. penile erection, loss of thermoregulation
If you wake up during this phase may experience briefly sleep paralysis
What functions are not inhibited in REM sleep?
Eye movements and trigeminal nerve function ergo you get teeth grinding
Essential for life, long term deprivation leads to death
Why is there thalamic inhibition during REM sleep?
This is when we deal with sensory input from the brain, do not want to act out these inputs
Why can homeless people die easily from hypothermia?
Inhibition of thermoregulation during REM sleep, can easily freeze to death due to hypothermia
Does not need to be sub zero temperatures, can be as warm as 10 degrees C
