Lecture 15 - Sleep Conciousness Flashcards
What is sleep?
Behaviorally
- quiescence
- decreased awareness of ext. environment
- typical stereotypic postures
- rapidly reversible (diff from anesthesiology)
Electrophysiologically
- used to define vigilance states of the brain
- wake, NREM (3 stages), REM
Polygraphic Monitoring
EEG measures voltage difference across scalp
- EEG = brain waves
- EOG = eye movements
- EMG = muscle tension
Physiology of NREM sleep
-increase parasympathetic activity
-decrease HR, CO, BP
-decrease tidal volume and minute ventilation
-decrease hypoxic ventilatory response (lower O2)
-increase PaCO2
-decrease activity of accessory muscles of respiration
decrease muscle activity (EMG)
Physiology of REM sleep
- increase sympathetic activity (phasic REM -> active eye)
- irregular breathing pattern
- decreased hypoxic respiratory response (lower O2)
- decrease in thermoregulation
- paralysis of skeletal muscle (except diaphragm)
- dreaming
Anterior hypothalamus lesion
profound insomnia
lesion between brainstem and forebrain
profound sleepiness
lesion in posterior hypothalamus
narcolepsy
Ascending arousal system (AAS)
Dorsal branch - start in brainstem and moves up
- pedunculopontine nucleus and laterodorsal tegmental nucleus (cholinergic pons) –> thalamus
- activates thalamic relay neurons –> cerebral cortex
Ventral branch - start in upper brainstem and hypothalamus
- monoaminergic neurons (orexin, ACh, dopamine,histamine, serotonin, NE)
- bypasses thalamus to go directly up to structures
- activates neurons in lateral hypothalamus and basal forebrain –> augmented and sent to cerebral cortex
von Economo’s “sleepy” lesion
bisecting arousal pathway –> makes you sleepy
VLPO
ventrolateral preoptic nucleus (ant. hypothalamus)
PROMOTES SLEEP
-inhibitory projections to AAS (both dorsal and ventral)
-innervates lateral hypothalamus and perifornical area
-lesion in ant. hypothalamus affects the VLPO nucleus and interrupts inhibiton of AAS –> causes insomnia
Orexin
AKA hypocretin
- produced in neurons in hypothalamus important for stabilizing sleep-wake transitions
- finger on the switch for wake and sleep
- lost in narcolepsy (sleep-wake teeter totter more freq)
Narcolepsy
CNS hypersomnolence
- excessive daytime sleepiness
- sleep paralysis
- imagery (caught between dream and wake)
- cataplexy (loss of muscle tone with emotional stimuli)
- automatic behaviors
Important NREM regions
VLPO
Thalamic Reticular nucleus
Basal forebrain
Basal Forebrain and slow waves
Adenosine increases in BF with sleep deprivation
- increases due to increased energy utilization and ATP hydrolysis
- Adenosine inhibits ACh neurons in BF, causes sleepiness
- PROMOTES SLOW WAVE SLEEP
- caffeine inhibits adenosine receptors –> more wakeful
Thalamic Reticular Nucleus
TRN crucial for sleep spindle formation
-GABAergic
Important REM regions
laterodorsal tegmental nucleus (LDT) peduculopontine nucleus (PPT) perilocus ceruleus supramammilary nucleus (SUM)
Laterodorsal tegmental nucleus and peduculopontine nucleus
LDT/PPT active during both REM and WAKE
2 populations of neurons
-REM-on: only active during REM, inhibited by AAS (serotonin)
-wake/REM-on: active during both
Locus coeruleus + dorsal raphe
part of AAS
- inhibits REM-on with serotonin
- turned off during REM sleep
- allows both REM-on and Wake/REM-on neurons to be active –> more cholinergic activity
- Antidepressants increase serotonin/NE in synaptic cleft and suppresses REM sleep
REM Sleep: muscle atonia
perilocus coeruleus cause hyperpol of spinal motor neurons –> cause muscle atonia (no tone–> little EMG)
REM Behabvior Disorder (RBD)
-usually lesion around the perilocus coeruleus –> lack of inhibition of spinal motor neurons –> lots of EMG
Circadian Rhythm 2-process model
Circadian clock (alerting signal) Sleep homeostat (sleep debt) -Interaction between these two processes gives different levels of "alertness:
Sleep deprivation affects process S (increase sleep debt) but not process C
Suprachiasmatic nucleus
master biological clock (central pacemaker for circadian r.)
just above the optic chiasm to get good light signals
PROMOTES WAKE and SUPPRESSES REM/sleep during active period (inhibits VLPO and stims orexin producing)
>activate locus coeruleus, which inhibits REM-on
Outputs of circadian timing
plasma melatonin (tells body time of day) -photic input to SCN via intrinsically photosensitive retinal ganglion cells that contain MELANOPSIN (blue-light photopigment) --> roundabout pathway to pineal gland
