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Neuroscience > L58 Sleep > Flashcards

L58 Sleep Flashcards

1
Q

what are the functions of sleep?

A
  • behavioral advantage
  • maintenance
  • maturation
  • memory processing
  • rest theory
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2
Q

what is the behavioral advantage of sleeping?

A

sleep protects us (with poor night vision) from predators

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3
Q

what is the maintenance function of sleep?

A

NREM sleep rests some neural circuits while REM sleep ensures activation of circuits

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4
Q

what is the maturation function of sleep?

A

REM sleep possibly involved in maturation of the nervous system

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5
Q

what is the memory processing function of sleep?

A

consolidation of short term memory to long term memory (good for passing exams)

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6
Q

what is the rest theory that is a function of sleep?

A

a necessary fall in neuronal activity and metabolic activity during NREM sleep

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7
Q

What are the different methods to study sleep?

A

EEG - with additional electrodes for heart rate, eye and body movements, respiration etc. (tells you about the cortical area)

PET, fMRI - to see changes in blood flow, metabolism

MEG - magnetoencephalography

EMG - electromyography

NCV - nerve conduction velocity

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8
Q

describe magnetoencephalography (MEG)

A

magnetic signals generated by neural activity

it localizes sources of neural activity better than EEG
it cannot provide detailed images like fMRI does…

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9
Q

what does the EEF record?

A

very small electrical fields generated by synaptic currents in PYRAMIDAL CELLS

records the synaptic activity of cortical neurons

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10
Q

describe desynchronized cortical activity and what type of brain is it associated with?

A 
causes low (voltage) amplitude EEG waves
normal awake brain
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11
Q

describe synchronized cortical activity and what type of brain is it associated with?

A

causes high amplitude EEG waves

sleeping brain

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12
Q

sleep is NOT a _____ physiological process

A

uniform

we have Day-night cycles
REM (paradoxical sleep) and NREM

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13
Q

what are the waves and EEG rhythms seen in sleep?

A

beta >12 Hz - activated cortex
alpha 8-12 Hz - quiet waking state
theta 4-8 Hz - some sleep states
delta 30 Hz - during wakefulness

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14
Q

what rhythms are seen when a person is awake with eyes closed?

A

alpha rhythm

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15
Q

what rhythms are seen when a person is awake with eyes open?

A

beta rhythm

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16
Q

what is the transition between alpha and beta rhythms in an awake person?

A

you will notice the blink artifact and that indicates when the eyes open

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17
Q

what rhythm is found in REM sleep?

A

Beta

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18
Q

what rhythm is found in stage 1 NREM sleep?

A

theta waves

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19
Q

what rhythms are found in stage 2 NREM sleep?

A

Spindle and K complex

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20
Q

what rhythms are found in stage 3 NREM?

A

delta

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21
Q

what rhythms are found in stage 4 NREM sleep?

A

delta

caused by inherent synchronous firing of cortical cells due to absence of sensory input + direct ARAS input

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22
Q

what is the normal sleep/wake cycle?

A

~90 min cycles
` 7 hours per night
**highly ordered structure

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23
Q

what stage of sleep is characterized by spindles and K complexes?

A

stage 2 NREM

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24
Q

define sleep spindle.

A

episodically appearing, spindle-shaped aggregate of 12-14 Hz waves with a duration of 0.5-1.5 seconds

identifies NREM stage 2 sleep

because of rhythmic firing of thalamocortical neurons due to decreased sensory and increase ARAS input

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25
Q

Define K complex.

A

sharp, negative, high voltage EEG wave, followed by a slower, positive component

it occurs spontaneously during NREM at the beginning and defining Stage 2 NREM

they can also be elicited during sleep by external (mostly auditory) stimuli

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26
Q

how much of total sleep time in a baby is REM

A

about half

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27
Q

how much of total sleep time in persons 15-75 years is REM?

A

about 20% of total sleep time

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28
Q

when is stage 4 NREM sleep maximum?

A

puberty

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29
Q

how much of total sleep does stage 4 NREM make up in early adulthood?

A

about 30%

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30
Q

how much of total sleep does stage 4 NREM make up in old age?

A

about 10% or less

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31
Q

the total about of time spent in sleep (REM and NREM) _____ with age

A

declines

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32
Q

when does REM sleep become more prominent?

A

towards morning

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33
Q

where is the biological clock located?

A

within the suprachiasmatic nucleus (SCN) in the anterior hypothalamus

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34
Q

each SCN neuron has about _____ hour cycle of activity

A

24-25

NO AP needed

Gene expression = Clock genes

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35
Q

how are the rhythms of the biological clock coordinated?

A

by the SCN based on light input from the outside world during daytime (excitatory input from retinal ganglion cells) and by influencing the activity of the pineal gland which secretes melatonin

36
Q

define hypnogram

A

continuous graphical record of the different sleep stages showing the periods spent in each stage

37
Q

what are the main CNS regions involved in the sleep-wake rhythm regulation?

A

nuclei in
-reitcular formation (in brainstem)

ascending - associated with consciousness

  • thalamus
  • hypothalamus
  • basal forebrain

descending
-cerebellum sensory systems

38
Q

define arousal

A

responsiveness of cortical and thalamic neurons to sensory stimuli (WAKEFULNESS)

39
Q

describe the ascending arousal system

A

functional ground of neurons in the brainstem, thalamus, hypothalamus and basal forebrain that maintains and raises excitability in cerebral cortex

40
Q

what is the brainstem part of the ascending arousal system often called?

A

ascending reticular activating system (ARAS)

41
Q

what makes up the ARAS?

A
  1. thalamocortical transmission
    - cholinergic structures
    - monoaminergic structures
  2. lateral hypothalamus, basal forebrain, and cerebral cortex
    - NA, serotonin, histamine
    - OREXIN/HYPOCRETIN***
    - ACh, GABA
42
Q

where is the ventral lateral pre-optic area/nuclei (VLPO) located and what is its function?

A

in hypothalamus (inhibitory GABA and galanin)

promotes sleep by inhibiting activity in the brain’s arousal centers

43
Q

what happen when the activity of the ARAS pathways to basal forebrain are depressed?

A

onset of sleep

44
Q

what happens when cholinergic cells are transiently activated during sleep?

A

onset of REM sleep

45
Q

list the sleep promoting agents?

A 
adenosine
melatonin
IL-1
muramyl peptides
delta sleep inducing peptide
eicosanoids (anti-inflammatory)
46
Q

where is adenosine a sleep modulator?

A

at the synpase

47
Q

what happens to adenosine concentrations in persons who are awake and sleeping?

A

awake - adenosine concentration increases which inhibits activity of ARAS

sleep - adenosine slowly decreases

when adenosine is administered = NREM sleep

48
Q

when does melatonin concentration reach its max?

A

2-3am

49
Q

when does melatonin concentration decline?

A

by 7 am

50
Q

how is melatonin synthesized?

A

tryptophan –> serotonin –> melatonin

51
Q

when is IL-1 produced?

A

during infections

52
Q

when does IL-1 concentration increase in CSF?

A

during NREM sleep

IV injection of IL-1 = NREM sleep

53
Q

describe how muramyl peptides promote sleep

A

its from bacterial cell walls

when injected into lateral ventricles of mammals = NREM sleep + fever and stimulation of immune system

54
Q

when happens when Delta sleep inducing peptide is injected IV?

A

NREM sleep

55
Q

when are pontine-geniculo-occipital (PGO) waves seen?

A

in periods of REM sleep when the EEG shows low amplitude and desynchronized (similar to that of awake state)

56
Q

why does REM sleep kind of look like awake state?

A

pontine cholinergic cells fire in bursts = PGO waves

CN 3 is excited (REM/eye movements)

inhibition of most limb motor neurons

57
Q

define the resistance to arousal in REM sleep

A

inhibition of transmission from the thalamus to the cerebral cortex in ALL specific sensory pathways (somatic, auditory).

58
Q

define the muscular relaxation in REM sleep

A

neurons in the reticular formation inhibit the motor neurons in the spinal cord, mediated by those reticulospinal fibers, which use glycine as an inhibitory transmitter at the level of spinal cord.

59
Q

what generates REM sleep?

A

generated by cells in the brainstem, particularly the pons, adjacent portions of the midbrain and hypothalamus

60
Q

describe REM-on cells

A

are maximally active
in REM sleep.

Subgroups of REM-on cells use the transmitters GABA, glycine, acetylcholine or glutamate.

61
Q

describe REM-off cells

A

are minimally active
in REM sleep.

Subgroups of REM-off cells use the transmitters norepinephrine, epinephrine, serotonin and histamine.

62
Q

Cognitive deficit persists for ______days after the period of sleep deprivation (more deficits after lack of NREM than REM sleep)

A

several

63
Q

do blind people suffer from sleep abnormalities?

A

yes

64
Q

what are the various disorders of sleep?

A

-Insomnia
-Sleepiness during the Day
-Periods of Sleep Apnea cause frequent Awakenings
-Parasomnias
-Sleep Disorders involving Abnormal
Movement
-Disordered Sleep in Alzheimer’s and Parkinson’s Diseases
-Treating Sleep Disturbances

65
Q

what known disorders are irregular sleeping behavior found in?

A
  • Epilepsy
  • Parkinson’s disease
  • Alzheimer’s disease
  • Prion diseases
  • Schizophrenia
  • Depression
  • Stress
  • Induced by alcohol and drugs
66
Q

what are the two types of insomnia?

A

transient (less than 3 weeks)
chronic (elderly, pts with pain, psych pt, familial disorder)

*insomnia may also be due to drugs or alcohol abuse

67
Q

what disorders of sleep fall under excessive sleepiness during the day?

A

Narcolepsy

  • rapid onset of REM sleep
  • cataplexy (sleep paralysis)
  • hypnagogic hallucinations (pre-sleep dreams)

Sleepapnea
-interruptions in breathing (> 10 seconds) hypoxia & hypercapnia

Fatal familial insomnia

Prion disease (autosomal dominant disorder) selective atrophy of thalamic nuclei
ANS: sympathetic overactivity
68
Q

describe parasomnias

A

Parasomnias (mostly observed in children)
-Sleepwalking & Sleep Terrors (usually in
stages 3 & 4 NREM)
-Nightmares (during REM)
-Sleep paralysis (often in narcoleptic patients)
-Sleep myoclonus (jerks, startle) occurs during the initial phases of sleep, especially at the moment of dropping off to sleep

69
Q

descibe Restless Legs syndrome

A

– Symptoms distantly resembling early Parkinson’s disease, but not caused by the same reasons
– Waking up after a short sleep, delays sleep onset
– During NREM periodic limb movements (PLMS) causing interruptions to sleep (benzodiazepines suppress arousals)
– Treated also by L-DOPA
– Keeping legs in cold, stretch, massage etc. may help
– Postulated problem: Iron metabolism (needed for an enzyme)
– NOT suffered only by elderly, occasionally
during pregnancy, can be of genetic origin

70
Q

describe REM behavior disorder

A
  • Failure of brainstem circuits to suppress muscular contraction during REM sleep
  • Potentially harmful effects of violent limb movements during REM sleep correlated with content of dreams
71
Q

what are tx options for sleep disorders?

A
  • Behavioural therapy => change of sleep routines or daily activity patterns. SLEEP IS NECESSARY FOR MEMORY FORMATION!!!!
  • Pharmacological => antidepressants, benzodiazepine and melatonin receptor agonists, dopamine agonists
  • Caffeine inhibits A1 adenosine receptors. But be aware of developing tolerance!
72
Q

neuronal activation in the HIPPOCAMPUS during REM sleep may play a role in?

A

memory

73
Q

The hippocampo-cortical activation during waking is followed by multiple waves of cortical ____ during full sleep cycles

A

plasticity

74
Q

• Early-life REM deprivation reduces______of hippocampal neuronal circuits, possibly by hindering expression of mature glutamatergic synaptic components

A

stability

75
Q

the 4 stages of NREM sleep have progressive _____ levels of consciousness (sync, low freq. waves in EEG)

A

decreasing

76
Q

periods of REM sleep have a ____ level of consciousness? (desync, high freq waves in EEG)

A

raised

77
Q

the fraction of sleep time spent in NREM peaks at ____

A

puberty

78
Q

the fraction of REM sleep time is ______ of age after puberty

A

independent

79
Q

sleep deprivation is damaging to ____ and ____ ability

A

cognitive and manual

80
Q

what is in the basal forebrain and brainstem that keeps us awake and alert?

A

the arousal system

81
Q

all sleep disorders lead to subnormal ___ and ___ performance during waking hours

A

mental and physical

82
Q

read about the documented abnormal people

A
  1. ♀ who sleeps for 1.5hours/night
  2. ♂ war veteran with shrapnel in his pons exhibits virtually no REM sleep
  3. ♂ observed in clinic experienced over 3hours of REM sleep
  4. ♂ stayed awake for 11 straight days without any Rx and had no permanent harmful effects
83
Q

how can sleep deprivation help those who are clinically depressed

A

have unusually large amounts of REM sleep where controlled deprivation can help alleviate their
symptoms either with behavior changes or Rx

84
Q

which is more significant in terms of the cognitive deficits seen: NREM deprivation or REM deprivation?

A

NREM

85
Q

lesions of the brainstem can induce?

A

sleep/coma

86
Q

how do general anesthetics lower consciousness?

A

by reducing the activity of the brainstem as part of the ARAS

87
Q

what is the onset of REM due to?

A

firing of the pontine cholinergic cells (part of ARAS) which ↓firing rate in locus ceruleus and ↓raphe nucleus as well as an ↑LGN excitability and ↑Occipital Cortex V1 (dreams)

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