Lecture 15 - Sleep Conciousness Flashcards Preview

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Flashcards in Lecture 15 - Sleep Conciousness Deck (22):
1

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

2

Polygraphic Monitoring

EEG measures voltage difference across scalp
-EEG = brain waves
-EOG = eye movements
-EMG = muscle tension

3

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)

4

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

5

Anterior hypothalamus lesion

profound insomnia

6

lesion between brainstem and forebrain

profound sleepiness

7

lesion in posterior hypothalamus

narcolepsy

8

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

9

von Economo's "sleepy" lesion

bisecting arousal pathway --> makes you sleepy

10

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

11

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)

12

Narcolepsy

CNS hypersomnolence
-excessive daytime sleepiness
-sleep paralysis
-imagery (caught between dream and wake)
-cataplexy (loss of muscle tone with emotional stimuli)
-automatic behaviors

13

Important NREM regions

VLPO
Thalamic Reticular nucleus
Basal forebrain

14

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

15

Thalamic Reticular Nucleus

TRN crucial for sleep spindle formation
-GABAergic

16

Important REM regions

laterodorsal tegmental nucleus (LDT)
peduculopontine nucleus (PPT)
perilocus ceruleus
supramammilary nucleus (SUM)

17

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

18

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

19

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

20

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

21

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

22

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