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16 Sleep and arousal

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					Sleep and Arousal

    Dr. K. Sivapalan
             Electroencephalogram.
• It is record of potentials in volume
  conductor as ECG. The changes are in
  micro volts as opposed to millivolts in ECG.
• Flow towards the electrode is positive and
  away is negative.
• The recorded waves represent oscillating
  currents within cortex and feed back
  circuits between thalamus and cortex.



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             Electroencephalogram.
                                            8-12 Hz. 50-100 μV
• Record of variations in
  the brain potentials
  recorded with                             18-30 Hz
  electrodes on the
  surface of the scalp.
• Electrocorticogram-                       4-7 Hz
  electrodes on the pial
  surface.

                                            <4 Hz

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             Normal EEG.




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               Variations in EEG.
      – Beta like activity is seen in infants but the occipital rhythm
        is 0.5-2 Hz.
      – This speeds up in childhood to typical theta rhythm.
      – The adult alpha pattern appears gradually in adolescence.




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             Mechanism of arousal.
• Arousal occurs on stimulation of any sensory input at
  receptor or pathway up to midbrain.
• Stimulation of the specific pathways above midbrain does not
  generate arousal.
• Collaterals of all sensory input activate reticular activating
  system [RAS] in brain stem which sends impulse to all parts of
  the cortex to generate arousal.
• Each sensory input produces two responses in the cortex-
  one fast response in the sensory cortex representing the
  stimulated area only. Then a second diffuse response is
  observed.
• Stimuli are processed in the cortex when awake but they
  cause arousal when in sleep.

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             Sleep.




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             Sleep Paterns.




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             Slow wave sleep.




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             REM Sleep.




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Didstribution of sleep stages.
• In a typical sleep, the person passes through
  the stages 1,2 and spends about 100 minutes
  in stage 3 and 4.
• Then REM follows and the cycle is repeated in
  about 90 minute intervals.
• Towards the morning, less stage 3,4 and more
  REM sleep.
• REM sleep: 80 % for preterm babies, 50 % for
  term babies, and 25 % in old age.

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             Sleep Time




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             Sleep disorders.




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Description: what is sleep and electroencephalogram patter during sleeping and types of sleeps and sleep disorders