Changing the way you learn

Sleep & Biological Rhythms

Stages of Sleep
1. Stage 1
  1. Light sleep, irregular low voltage waves
2. Stage 2
  1. Sleep Spindle
    1. Short bursts of 12-14Hz waves
  2. K-Complex
    1. Sharp high amplitude negative waves, smaller slow positive waves
3. Stage 3 & 4
  1. Slow, large amplitude waves
  2. Deepest sleep
4. REM Sleep
  1. Function
    1. Discards useless connections formed in the day
      1. Assists in memory formation & motor skills
        Moving eyes increase O2 supply to cornea
      2. Irritability, anxiety, impaired concentration
        Rats die from no REM sleep
  2. Desynchronized EEG activity
  3. Rapid eye movements
  4. Muscular paralysis
  5. REM Rebound
5. 1 Cycle = 90mins
Brain Activity
1. Measurements
  1. EEG
    1. Electroencephalograph
      1. measures electrical potentials by synchronicity
        net avg of all neuron activity
  2. EMG
    1. Electromyogram
      1. electrical potential recorded from electrode placed on muscle
        detects muscle movement
  3. EOG
    1. Electro-oculogram
      1. electrical potential recorded from electrode placed around eye
        detects eye movements
        REM Sleep
2. Alpha
  1. Relaxation
    1. Smooth, 8-12Hz
3. Beta
  1. Arousal
    1. Fairly slow, 13-30Hz
4. Theta
  1. Stage 1 & REM
    1. 3.5-7.5 Hz
5. Delta
  1. Stage 3 & 4
    1. Less than 4Hz
Wakefulness & Arousal
1. Neurotransmitters
  1. ACh
    1. Key player, keeps you awake but triggers REM
    2. Pons & Basal Forebrain
    3. produce activation & cortical desynchrony
      1. Faster REM
  2. NE
    1. Keeps you awake
    2. Catecholamine agonists produce arousal & sleeplessness
      1. Locus Coeruleus in dorsal pons
  3. 5-HT
    1. Activates Behavior
      1. Raphe Nuclei
        NE & 5HT disrupts REM
2. Physiological Mechanisms
  1. Hypocretin
    1. Peptide (orexin) produced by neurons located in hypothalamus
      1. Orexin = motivation to stay awake
        Destruction = narcolepsy
  2. VLPA
    1. Group of GABA neurons in preoptic area, activity suppresses alertness & behavioral arousal, promotes sleep
      1. Destruction = total insomnia, coma, death in rats
Endogenous Cycles
1. Endogenous: generated by body
  1. Circadian Rhythm
    1. wakefulness & sleep
      1. hormones secretion
  2. Circannual Rhythm
    1. mostly in animals
  3. Allows conservation of energy for future possible events
Sleep Abnormalities
1. Insomnia
  1. Onset, Maintenance, Termination
2. Sleep Apnea
  1. Inability to breathe while asleep
    1. Narrow Airway (obese)
    2. Brain mechanisms for respiration fail (elderly)
3. Narcolepsy
  1. Sudden attacks of sleepiness
    1. Hypnagogic hallucinations
      1. ACh, Orexin deficiency
      2. Pemoline (Cylert)/Ritalin may relieve sleep but cause other problems
4. Periodic Limb Movement Disorder
  1. Involuntary movement of limbs
    1. Middle age & elderly
    2. Tranquilizers sometimes
5. REM Behavior Disorder
  1. Vigorous movement during REM
6. Night Terrors
7. Sleep Talking/Walking
SCN Damage
1. Suprachiasmatic Nucleus
  1. Part of hypothalamus, bilateral
    1. Source of endogenous rhythm
      1. Damage = inconsistent rhythm, no light/dark synchrony
Chemical Control
1. Adenosine
  1. Produces Sleepiness
    1. Caffeine inhibits
2. Prostoglandins
  1. Promotes Sleep
    1. Inhibits Hypothalamus cells that + arousal
3. Basal Forebrain & Hypothalamus
  1. Promotes sleep, release GABA
    1. Prolonged wakefulness if damaged
      1. Anesthesia increases GABA receptors
Function of Sleep
1. Repair & Restoration
  1. Repair itself after exertions of the day
2. Evolutionary
  1. Sleep conserves energy to search for food & keep safe from predators
Brain Structures of Wakefulness & Arousal
1. Reticular Formation
  1. Medulla > Forebrain
    1. Lesions = v arousal
      1. NE
  2. Pontomesencephalon
    1. Stimulation = + arousal
2. Locus Coeruleus
  1. In pons
    1. Important for info storage (hippocampus)
      1. Mostly inactive during sleep (why we forget dreams)
3. Basal Forebrain & Axons
  1. To thalamus & cerebral cortex
    1. + Arousal
      1. Damage = Alzheimers
        ACh
4. Hypothalamus
  1. Stimulates arousal w histamine

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Sleep & Biological Rhythms

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	Created by Zaneta Chan about 8 years ago