Sleep - structures + chemicals involved

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  • Created by: Joanna
  • Created on: 04-12-13 17:08

Structures

Outputs from SCN:

  • subparaventricular zone (SPZ)
  •  dorsomedial nuclues of the hypothalamus (DMH)

Multistage pathway connecting SCN

ascending arousal system

via SPZ + DMH regul8s circadian rhythms of sleep + other bhvrs.

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Reticular activating system (RAS) / Reticular form

RAS 

  • column of brain tissue extends from spinal cord to midbrain
  • pass thru brainstem
  • small clusters of neurones + fine branching network of fibres
  • high r8 of firing its cholinergic fibres when awake + REM
  • small r8 of RAS during NREM
  • when RAS cells activ8d, EEG shows alpha type waves
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Locus Coeruleus

  • part of the pons
  • involved w/ increasing animal's sensitivity to its environment
  • increased activity of noradrenergic neuroes :associ8ed w/ wakefulness
  • decreased activity involved w/ onset of REM sleep
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Raphe Nucleus

  • part of the medulla + pons
  • important role in wakefulness
  • blocks activity of neurones active in REM sleep
  • serotonin - plays a role in triggering sleep
  • serotonin influence neurones of preoptic nucleus
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Preoptic nucleus + SCN

SCN - circadian patterns

destroying scn - disrupts the sleep wake cycle

implicated in insomnia

preoptic nucleus - close to the SCN + receives direct input from retinal fibers - input from eyes

light activating areas in retinal fibres - influential in sleep-wake cycle

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Cholinergic mesopontine nuclei

- projects to the thalamus

- cholinergic mesopontine nuclei produces acetylcholine

- reduces activity of thalamic reticular nucleus - sleep system

- activ8s thalamocortical neurons involved in wakefulness

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Chemicals involved in sleep

Nucleus involved in wakefulness:

  • Mesopontine nuclei - acetylcholine - active neurones
  • Locus Coeruleus - noradrenaline - active neurones
  • Raphe nuclei - serotonin - active neurones

NREM sleep

  • Mesopontine nuclei - acetylcholine - inactive neurones
  • Locus Coeruleus - noradrenaline - less active neurones
  • Raphe nuclei - serotonin - inactive neurones

REM sleep - on

  • Mesopontine nuclei - acetylcholine - PGO waves
  • Locus Coeruleus - noradrenaline - inactive neurones
  • Raphe nuclei - serotonin - inactive neurones

REM sleep - off

  • Locus Coeruleus - noradrenaline - less active neurones
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REM sleep structures / areas

Primary visual cortex:

- conscious visual signals when awake

Extrastriate visual areas:

  • - decode complex visual scenes
  • - significantly more active during REM sleep

Prefrontal cortex:

- thought + judgement

Limbic system

  • - active in REM
  • - amygdala [emotion]
  • - hippocampus [memory]

Anterior cingulate gyrus

  • attention + motivation
  • active during REM sleep

The pons

  • active during REM
  • REM sleep triggered by certain nuclei in the pons
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Electrical brain potentials - levels of arousal +

Electroencephalography [EEG] - electrical activity in brain

Electro-oculography [EOG] - eye movements

Electromyography [EMG] - records muscle activity

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Types of sleep

Slow-wave sleep [SWS] 

  • 4 stages
  • characterized by slow-wave EEG activity

Rapid-eye-movement sleep [REM] 

  • small amplitude
  • fast EEG waves
  • no postural tension
  • rapid eye movements
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Brain waves:- low to high frequency

Delta waves up to 4Hz

  • frontally in adults
  • posterior in children
  • adults slow wave sleep 
  • 3-4 SWS stage

Theta waves 4-7Hz 

  • drowsiness in older children + adults
  • 1-2 SWS stage

Alpha waves 8-12Hz

  • posterior regions of head, both sides
  • higher in amplitude on dominant side
  • central sites c3-c4 @ rest
  • closing eyes by relaxation
  • 1 SWS stage
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Brain waves:- low to high frequency 2

Beta waves 12-30Hz

  • both sides
  • symmetrical distribution
  • most evident frontally

Gamma waves 26-100Hz

  • certain cognitive / motor functions

Pontogeniculooccipital [PGO]waves

  • pons/geniculate [auditory/occipital vision]
  • spiky waves during REM sleep
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Human sleep - diff stages

Pattern of activity in awake 

dominated by waves of fast freq + low amplitude : 15-20 Hz

beta activity / desynchronised EEG

alpha rhythm - during relaxation

regular oscillation

8 - 12 Hz

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Stages of slow-wave sleep

Stage 1 sleep

  • events of irregular freq + smaller amplitude / vertex spikes / sharp waves
  • heart r8 slows, muscle tension reduces, eyes move about
  • lasts several mins

Stage 2 sleep

  • defined by waves of 12-14 hz - occur in burts = sleep spindles
  • K complexes appear - sharp -ve EEG potentials

Stage 3 sleep

  • continued sleep spindles as in stage 2
  • appearance of large amplitude , slow waves = delta waves
  • delta waves - once / second 

Stage 4 sleep

  • Delta waves - present about half the time

REM SLEEP follows:

  • active EEG w/ small amplitude, high freq waves like an awake person
  • muscles = relaxed = paradoxical sleep
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Adult sleep

Typical night

  • sleep time ranges : 7-8 hrs
  • 45-50% = stage 2 sleep
  • 20% = REM sleep
  • Cycles last 90-110 mins 
  • cycles early in night = more stage 3 + 4 SWS
  • later cycles = REM sleep
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Dreams and nightmares

Vivid dreams during REM sleep

  • visual imagery 
  • sense that dreamer is in the scene

Nightmares: 

  • frightening dreams 
  • awaken the sleeper from REM sleep

Night terrors:

  • sudden arousals from stage 3/4 SWS 
  • fear + autonomic activity
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Sleep patterns change across the life span

Mammals sleep more during infancy > adulthood

Infant sleep:

  • shorter sleep cycles
  • more REM sleep
  • 50% - provide essential stimulation to the developing nervous system

Aging people - total time asleep = declines + # of awakenings increases

  • Most dramatic decline = loss of time spent in stages 3 + 4
  • age 60 : only 1/2 as much time spent at age 20 by age 90 stages 3 + 4 = disappeared
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