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Week 6: Sleep - Coggle Diagram

- - - - Intrinsically photosensitive retinal ganglion cells (ipRGC)
        
        contain a photopigment called melanopsin
        
        forms the retinohypothalamic pathway from the retina to the SCN
    - - distinguishes between day and night and is most active in day
        
        regardless of activity patterns
        
        cathemeral (:sunny: and :crescent_moon:)
        
        crepuscular
        (active in twilight)
        
        SCN activity generates SNS response
        
        SNS response affects amount of melatonin synthesised by pineal gland
        
        :arrow_down: SNS activity leads to :arrow_down: melatonin made
        
        :arrow_up: SNS activity leads to :arrow_up: melatonin made
      - master clock that coordinates peripheral clock activity
        
        Rat experiments
        
        SCN cells adjust in 1 to 2 cycles
        
        Lung and muscle tissues require 6 cycles
        
        Liver tissues require more than 16 cycles
    - - isolated SCN tissue cultures have brain activity fluctuations that match source animal circadian rhythms
      - Hamsters exhibit cycle length of transplanted SCN
    - - most active at :crescent_moon:
      - finely tunes SCN circadian activity
        
        disabling astrocytes leads to slight lengthening of circadian rhythms
  - - - releases mRNA into the cytoplasm to produce PER proteins
        
        PER proteins :arrow_up: at :crescent_moon: and :arrow_down: in the :sunny:
    - - produces TIM proteins
        
        TIMs bind with PERs to form a PER/TIM complex
        
        PER/TIM complex can enter nucleus and inhibit period gene
  - - - helpful in regulating sleep patterns for individuals with visual impairments
      - has antioxidant properties
        
        can potentially improve symptoms in neurodegenerative disorders such as Alzheimer's
      - melatonin receptors in cells are involved in immune system
        
        potentially improve immune function
  - - - stress-induced cortisol associated with poor sleep quality
      - associated with jet lag effects
        
        flight crew that cross over 8 time zones have 33% more cortisol in saliva than ground crew
    - - mobilise energy stores
      - higher heart rate
      - higher blood pressure
  - - - released during Stage 3 of nREM sleep
      - peaks during puberty onset and drops after 21
      - reduced by sleep deprivation
    - - stimulates physical growth in children
      - building muscle and bone mass
      - maintaining immune system function
- - - - individual differences in circadian patterns
        
        Lark, night owl, in-between
      - many switch to owl chronotype in teens
        
        dramatic drop in melatonin on onset of puberty
        
        revert back after puberty possibly due to maturation of sleep regulation brain regions
      - Disruptions
        
        Shift Maladaptation Syndrome
        
        Demographic
        
        affects middle-aged and older workers the most
        
        experienced by individuals working evening or night shifts
        
        affects larks more than night owls
        
        Symptoms
        
        excessive sleepiness at work,
        impaired sleep at home
        
        health, personality, mood and interpersonal problems
        
        Work impactss
        
        nurses on night shift make 30% more errors
        
        higher accident rates in night shifts
        
        Jet Lag
        
        arises from crossing time zones
        
        Symptoms
        
        Irritability :angry:
        
        Sleepiness :zzz:
        
        Chronic Jet Lag
        
        flight attendants that crossed time zones weekly for 4 or more yrs
        
        :arrow_down: Reaction Time
        
        9% more mistakes
        
        Temporal lobe atrophy without sufficient recovery time
        
        easier to adjust to phase-delays than phase-advances
        
        Phase-Delays
        
        travelling West
        
        later shifts than usual
        
        Phase-Advances
        
        travelling East
        
        earlier shifts than usual
        
        Daylight Savings Time
        
        shift clock 1 hour back in fall :maple_leaf: (phase-delay)
        
        shift clock 1 hour forward in spring :four_leaf_clover: (phase-advance)
        
        produces jet lag symptoms for a few days
        
        associated with cardiovascular disease
        
        sleep deprivation leading to :arrow_up: SNS activation and
        :arrow_up: inflammation
  - - - entrain internal biological clocks to 24-hour cycle of earth rotation
      - Free-running circadian rhythms
        
        24.2 to 24.9 hours
        
        occur in absence of light and causes severe sleep disruptions
      - Relation to Food :meat_on_bone:
        
        :arrow_up: effective when there is enough food
        
        :arrow_down: effective when there is food shortage
- - - - Cholinergic
        mesopontine nuclei
        
        found in midbrain reticular formation
        
        secrete acetylcholine
        
        found in junction of the pons (pontine) and midbrain (meso)
        
        communicates with thalamus which moderates cerebral cortex activity and amount of sensory input received
    - - Medulla :arrow_right: Hypothalamus :arrow_right: basal forebrain
    - - secretes most of the brain's norepinephrine
      - has connections to the thalamus, hippocampus and cortex
      - :arrow_up: activity with alertness
    - - important in managing sleep-wake cycles
      - communicates with preoptic area, SCN and cerebral cortex
      - :arrow_up: activity with alertness
  - - - mind wandering
      - recalling personally relevant memories
      - planning future events
      - thinking about beliefs, intentions and motivations of others
        
        overlap of DMN structures with those involved in social behaviour
      - Sharing or understanding personal stories and experiencing fictional situations
        
        Integrating internal thoughts and external stimuli to establish a context for understanding situations
    - - useful predictor of cognitive function
      - peaks in adulthood and is lower in childhood and older age
      - unusual DMN activity implicated in neurodegenerative and psychological disorders
  - - - Functions
        
        manage homeostatic control of wakefulness
        
        inhibits waking pathways
      - aka NREM-on cells
        
        stimulation :zap: of POA cells produces immediate NREM sleep
        
        lesions result in insomnia
      - :arrow_down: activity during waking and REM
    - - synchronises cortical neuron activity in absence of waking circuit activity
      - electrical stimulation in waking animals produces NREM sleep
    - - decoupling of anterior parts from posterior parts
      - possibly associated with reduced consciousness during deep sleep
  - - - high levels of activity during REM and waking
      - electrical stimulation produces desynchronous activity
        
        due to connections with thalamus and cortex
    - - Rostral Pontine Reticular Formation
        
        found in the pons
        
        lesions in the area inhibit REM sleep
        
        active during REM while inactive in waking and REM
        
        PGO waves
        
        :one: PRF stimulates superior colliculi, which communicates with different area of PRF
        
        Responsible for coordinating eye movement timing and direction
        
        :two: Lateral Geniculate nucleus is activated
        
        visual centre of the thalamus
        
        :three: Occipital lobe
        is activated
        
        visual experiences are triggered
        
        location of the primary visual cortex
        
        associated with rapid eye movements
        
        Muscular Paralysis
        
        Inhibitory signals from PRF :arrow_right: medulla :arrow_right: spinal cord motor systems
    - - Locus Coeruleus
      - Raphe Nuclei
      - reduction in REM-off area activity permits REM-on area activity
        
        allows REM to occur
        
        REM-off areas reactivate after 30min of REM, inhibiting REM-on areas
    - - :arrow_up: activity in
        
        V2 (secondary visual cortex)
        
        Hippocampus
        
        suggests REM significance in memory consolidation
        
        Limbic System
        
        underlie emotional content of dreams
        
        DMN
        
        basis for self-referential aspect of dreams
        
        lower DMN activity associated with rapid eye movements
      - :arrow_down: activity in
        
        frontal lobe
        
        possible reason for illogical nature of dreams
        
        parietal lobe
- - - - associated with high alertness and active information processing
      - rapid waves of 14 to 30 Hz
      - highly irregular and low amplitude
      - prominent in the front of the brain
    - - slightly slower than beta waves with 8 to 13 Hz
      - more regular and larger amplitude
      - Mu Waves
        
        frequency overlaps with alpha at 9 to 11 Hz
        
        localised in the motor cortex
        
        observed at rest but suppressed by movement
      - prominent in the back of the brain (visual cortex)
      - associated with relaxation
        
        closing eyes can initiate alpha wave activity
    - - more than 30 cycles per second
      - obvious during sensory and visual processing
  - - - alpha waves replaced by theta wave activity
      - :arrow_down: in heart rate and muscle tension
      - Emergence of sleep myoclonia
    - - Sleep spindles
        
        produced by interactions between the thalamus and cortex
        
        12 to 14 Hz
        
        last around 0.5 seconds
      - K complexes
        
        made of single delta waves
        
        occur randomly or in response to unexpected stimuli (eg. loud noises)
      - accounts for 50% of sleep
    - - features delta wave activity (1 to 4 Hz)
      - Brain energy usage decreases to 11% to 40% of waking brain
      - PNS activity lowers blood pressure, heart rate, breathing, body temperature
      - Sharp-wave ripples
        
        occur in the hippocampus
        
        rapid bursts of waveforms
    - - vivid dreaming
      - features waking beta activity and theta activity in the hippocampus
      - brain energy usage increases to or beyond wakefulness levels
      - SNS activation
        
        increase in blood pressure, breathing and heart rate
      - increased blood flow in genital areas
      - major postural muscles are immobilised while smaller muscles can still twitch
        
        fingers twitching indicates muscular inhibition stronger at beginning of REM and gradually decreases
      - rapid eye movements
        
        only occur during 14%-27% of REM
        
        experienced by people with congenital blindness
    - - 1st 4 hours
        
        longer periods of NREM and short REM periods
        
        Stage 3 NREM is dominant
      - Next 4 hours
        
        REM is dominant stage
        
        Any NREM will be in Stages 1 to 2
        
        Stage 3 NREM infrequent or absent
- - - - :arrow_up: in waking and REM sleep but :arrow_down: in NREM sleep
      - possibly promotes REM-on processes
    - - :arrow_up: in waking and REM sleep but :arrow_down: in NREM sleep
      - released by pons and basal forebrain
      - cholinergic agonists :arrow_up: mental awareness
        
        Eg. nicotine :smoking:
    - - major neurochemical used by neurons in the thalamus and the hypothalamus
        
        neuron activity associated with alertness
      - :arrow_up: activity in waking and :arrow_down: in NREM and REM sleep
      - Antihistamines
        
        Traditional ones produce drowsiness :sleepy:
        
        Modern ones do not cross blood-brain barrier and do not induce drowsiness
    - - blocks adenosine receptors
      - promotes alertness
    - - Norepinephrine produced by locus coeruleus
      - Serotonin produced by raphe nuclei
      - antidepressant drugs boost both and thus suppress REM
      - Highest in wakefulness and lowest in REM
  - - - :arrow_up: throughout the day and until sleep occurs and :arrow_down: during sleep
      - prevents secretion of neurochemicals associated with waking
        
        eg. ACh, norepinephrine, serotonin
      - ATP byproduct that inhibits many brain systems