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Neuroanatomy > Lecture 15 - Sleep Conciousness > Flashcards

Lecture 15 - Sleep Conciousness Flashcards

1
Q

What is sleep?

A

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
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2
Q

Polygraphic Monitoring

A

EEG measures voltage difference across scalp

  • EEG = brain waves
  • EOG = eye movements
  • EMG = muscle tension
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3
Q

Physiology of NREM sleep

A

-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)

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4
Q

Physiology of REM sleep

A
  • 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
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5
Q

Anterior hypothalamus lesion

A

profound insomnia

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6
Q

lesion between brainstem and forebrain

A

profound sleepiness

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7
Q

lesion in posterior hypothalamus

A

narcolepsy

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8
Q

Ascending arousal system (AAS)

A

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
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9
Q

von Economo’s “sleepy” lesion

A

bisecting arousal pathway –> makes you sleepy

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10
Q

VLPO

A

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

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11
Q

Orexin

A

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)
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12
Q

Narcolepsy

A

CNS hypersomnolence

  • excessive daytime sleepiness
  • sleep paralysis
  • imagery (caught between dream and wake)
  • cataplexy (loss of muscle tone with emotional stimuli)
  • automatic behaviors
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13
Q

Important NREM regions

A

VLPO
Thalamic Reticular nucleus
Basal forebrain

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14
Q

Basal Forebrain and slow waves

A

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
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15
Q

Thalamic Reticular Nucleus

A

TRN crucial for sleep spindle formation

-GABAergic

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16
Q

Important REM regions

A 
laterodorsal tegmental nucleus (LDT)
peduculopontine nucleus (PPT)
perilocus ceruleus 
supramammilary nucleus (SUM)
17
Q

Laterodorsal tegmental nucleus and peduculopontine nucleus

A

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
Q

Locus coeruleus + dorsal raphe

A

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
Q

REM Sleep: muscle atonia

A

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
Q

Circadian Rhythm 2-process model

A 
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
Q

Suprachiasmatic nucleus

A

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
Q

Outputs of circadian timing

A 
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

Neuroanatomy (18 decks)

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