Chapter 09: Wakefulness & Sleep


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Physiological cycles leading to sleep and wakefulness; what happens as we sleep?; why do we sleep and dream?

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Chapter 09: Wakefulness & Sleep

  1. 1. Rhythms of Wakefulness & Sleep
  2. 2. Endogenous Cycles <ul><li>Endogenous Circannual Rhythm </li></ul><ul><li>Internal calendar which prepares a species for annual seasonal changes </li></ul><ul><li>Endogenous Circadian Rhythm </li></ul><ul><li>Internal rhythm lasting about a day </li></ul><ul><li>In humans the circadian rhythm is about 24.2 hours </li></ul>
  3. 3. Mechanisms of the Biological Clock <ul><li>Suprachiasmatic Nucleus </li></ul><ul><li>Above the optic chiasm in the hypothalamus </li></ul><ul><li>Controls rhythms through the regulation of 2 genes: period & timeless </li></ul><ul><li>Code for proteins Per & Tim which are low & increase during the day but increase in the evening causing sleepiness </li></ul><ul><li>Melatonin </li></ul><ul><li>A hormone released by the pineal gland, mainly at night, increasing sleepiness </li></ul><ul><li>Stimulates receptors in the SCN to reset the biological clock </li></ul>
  4. 4. Stages of Sleep Stage 1 Stage 2 Stages 3 & 4 Light sleep with slowed brain wave patterns & the presence of irregular, jagged low-voltage waves Sleep spindles & K-complexes Slow-wave sleep Comprised of slow, large amplitude waves
  5. 5. Paradoxical or REM Sleep <ul><li>REM Sleep </li></ul><ul><li>Characterized by repeated eye movements, fast low-voltage brain waves with & breathing & heart rates similar to Stage 1 sleep </li></ul><ul><li>N-REM Sleep </li></ul><ul><li>The stages of sleep other than REM </li></ul><ul><li>Cycling Through the Stages </li></ul><ul><li>Upon falling asleep you enter Stage 1 </li></ul><ul><li>Cycle through Stages 2, 3 & 4 </li></ul><ul><li>After 60 to 90 minutes you cycle back through 4 through 2 and enter REM sleep </li></ul><ul><li>After entering REM sleep, the sleep cycle sequence repeats with each cycle lasting 90 minutes </li></ul><ul><li>REM sleep is associated with dreams but dreams can occur in n-REM sleep </li></ul>
  6. 6. Wakefulness & Arousal in the Brain <ul><li>Reticular Formation </li></ul><ul><li>Extends from Medulla into Forebrain </li></ul><ul><li>Lesions decrease arousal </li></ul><ul><li>Pontomesencephalon </li></ul><ul><li>Part of the Reticular Formation contributing to cortical arousal </li></ul><ul><li>Stimulation awakens sleeping or increases alertness in one awake </li></ul><ul><li>Locus Coerulus </li></ul><ul><li>In the pons, emits impulses releasing norepinephrine in response to meaningful events </li></ul><ul><li>Important for storing information </li></ul><ul><li>Basal Forebrain </li></ul><ul><li>Release acetylcholine </li></ul><ul><li>Damage decreases arousal, impairs learning & attention & increases time spent in n-REM sleep </li></ul>
  7. 7. Abnormalities of Sleep <ul><li>Insomnia </li></ul><ul><li>Problems falling or remaining asleep </li></ul><ul><li>3 categories of insomnia: </li></ul><ul><li>Onset Insomnia – trouble falling asleep </li></ul><ul><li>Maintenance Insomnia – waking up frequently during the night after falling asleep </li></ul><ul><li>Termination Insomnia – waking up too early & cannot go back to sleep </li></ul><ul><li>May be due to biological rhythm abnormalities or the use of sleeping pills </li></ul>
  8. 8. Abnormalities of Sleep <ul><li>Sleep Apnea </li></ul><ul><li>The inability to breathe during sleep </li></ul><ul><li>Common cause is obesity </li></ul><ul><li>Possible cause of SIDS </li></ul><ul><li>Obstructive Apnea is most common type & related to snoring </li></ul><ul><li>Central Apnea is related to a CNS problem & is inherited </li></ul>
  9. 9. Abnormalities of Sleep <ul><li>Narcolepsy </li></ul><ul><li>Frequent, unexpected periods of sleepiness during the day </li></ul><ul><li>Symptoms: gradual or sudden attacks of sleepiness, cataplexy, sleep paralysis & hypnogogic hallucination </li></ul><ul><li>Symptoms interpreted as REM sleep intruding into wakefulness </li></ul><ul><li>Overactive acetylcholine synapses & deficiency of orexin are 2 possible explanations </li></ul><ul><li>Treatments: stimulants (pemoline or methylphenidate </li></ul>
  10. 10. Abnormalities of Sleep <ul><li>Periodic Limb Movement Disorder </li></ul><ul><li>Involuntary movements of the legs that can cause insomnia </li></ul><ul><li>Occurs during nREM sleep </li></ul><ul><li>Treatment: Tranquilizers </li></ul><ul><li>REM Behavior Disorder </li></ul><ul><li>Vigorous movement during REM sleep apparently acting out the dreams </li></ul><ul><li>Probably due to the inability of the pons to inhibit spinal motor neurons </li></ul>
  11. 11. Abnormalities of Sleep <ul><li>Night Terrors </li></ul><ul><li>Abrupt, anxious awakening from a nREM sleep </li></ul><ul><li>More common in children than in adults </li></ul><ul><li>Sleep Talking </li></ul><ul><li>Can occur in REM or nREM sleep </li></ul><ul><li>Harmless </li></ul><ul><li>Sleep Walking </li></ul><ul><li>Usually in Steges 3 or 4 sleep </li></ul><ul><li>Early in the night </li></ul><ul><li>More common in children </li></ul>
  12. 12. The Functions of Sleep <ul><li>Repair & Restoration Theory of Sleep </li></ul><ul><li>The body, especially the brain, requires sleep to repair itself after the exertion of the day </li></ul><ul><li>Evolutionary Theory of Sleep </li></ul><ul><li>Sleep is to save energy when we would otherwise be energy inefficient, such as at night </li></ul>
  13. 13. The Functions of REM Sleep <ul><li>Amount of REM Sleep </li></ul><ul><li>The Amount of REM sleep is associated with the total amount of sleep you get </li></ul><ul><li>Deprivation of REM Sleep </li></ul><ul><li>Deprivation of REM sleep leads to increased attempts at REM sleep </li></ul><ul><li>REM Sleep & Memory </li></ul><ul><li>REM sleep is implicated in memory storage & as a way of getting oxygen to the corneas of the eyes </li></ul>
  14. 14. Biological Perspectives on Dreaming <ul><li>Activation-Synthesis Hypothesis </li></ul><ul><li>During sleep, many brain regions become activated, so the brain creates a story to make sense of the activity </li></ul><ul><li>Clinico-Anatomical Hypothesis </li></ul><ul><li>Either internal or external stimulation activates parts of the parietal, occipital, & temporal cortex </li></ul><ul><li>No visual information overrides the stimulation & no criticism of the prefrontal cortex censures it, so it develops into hallucinatory perceptions </li></ul>