Circadian Rhythm - Circa die--about a day

• Many body functions fluctuate about fairly stable cycle
• Man--diurnal; cats, rats, bats, etc.--nocturnal
• Mollusks -- tides; 28-day cycle of female & moon
• Body temperature varies during a day cycle
• Some chemical cycles shift; others do not
• In non-day or -night environment: Cycle may shift
• fatigue not due to sleep loss, but body cycle shifts (e.g., temperature).
• Pilots--shift in time zones
• Premature aging--stay up longer
• Rotational shift -- adjustment may take two weeks
• Response to drugs, temperature and X-ray depends on time of day

Electroencephalographic Recordings

• Not unitary process but progression of cycles.
• Alpha rhythm -- relaxation, eyes closed
• Stage I -- low voltage fast activity; relaxed
• Stage II - spindles & K-complex
• Stage III -- slow (delta waves» 1/sec» heart rate slows, temperature drops)
• Stage IV -- delta sleep (increased with exercise)
  • Most of time during first half of night
  • Sleep walk
  Paradoxical sleep -- REM (rapid eye movement)
  • Very deep but like phase I
  • REM -- correlated with dreaming (memory)
  • Approximately 1 minute duration&; 4 times per night.
  • Muscle tone disappears
  • Eye movements
  • Adults don't go directly into REM sleep

Passive Theories of Sleep

• All mammals & birds sleep
• ARAS reduced activation results in sleep
• Not inactivation of ARAS units, but of its effect on cortex
• Supported by lesion studies
• Wakefulness system (ARAS) stops working

Active Theory of Sleep

• Suprachiasmic Nucleus (primary biological clock)
  • Receives input from retina and lateral geniculate
• Basal forebrain region - damage: total insomnia;
  • Stimulation: drowsiness & sleep
• Nuclei of Raphe -- source of serotonin supply
  • Lesions -- cats become sleepless
  • Serotonin is important (inhibits REM sleep)
• Slow wave sleep -- effect of serotonin on the nervous system (cortex important)

Paradoxical Sleep (REM)

• Differs from slow-wave sleep in that there is a disappearance of tone
• REM sleep abolished by lesions in locus coeruleus
• These cells contain noradrenalin
• Locus coeruleus controls paradoxical sleep
• Regardless of activity of CNS, there is a lack of muscle tone due to secretion of noradrenalin
• PGO waves: first manifestation of REM sleep (pons, geniculate, occipital)
  • Function of REM sleep
  • Removal of biochemical substance
  • May be monoamine oxidase (MAO);
  • Drug inhibiting MAO can suppress REM sleep
• Raphe ->light sleep (secreting serotonin)
• Locus coeruleus -> deep sleep (noradrenalin)

Sleep Deprivation

• REM deprivation
  • increased frequency of occurrence, duration & intensity of REM
  • Decrease in seizure threshold, & progressive rise in heart rate
  • Increased activity, food motivation, sexual behavior
  • No major emotional problems
• Delta sleep-deprivation
  • Prolonged sleep deprivation (+48 hrs) results in severe mental disturbance, attention deficit, withdrawing, visual complaints, hallucinations, and time distortion
  • After 5 days, severe distortion; may end up in mental institution
  • Technique used in combat and "brain-washing"

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  Terms to Know

  Circadian rhythm	Monoamine oxidase	Noradrenalin
  REM sleep	Serotonin	Locus coeruleus
  Delta sleep	alpha rhythm	stage II sleep
  Raphe Nuclei	basal forebrain region	stage IV sleep
  suprachiasmic nucleus	REM deprivation	narcolepsy

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  Links to Associated Areas

  LINK Sleep Basics