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Outline. Sleep and the brain Sleep patterns How much sleep do you need? Biological Rhythms Circadian Clock Entrainment of the Circadian Clock Body temperature. Sleep and the Brain. Sleep is controlled by many brain regions: The hypothalamus is important in the control of NREM sleep.

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Outline

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  1. Outline • Sleep and the brain • Sleep patterns • How much sleep do you need? • Biological Rhythms • Circadian Clock • Entrainment of the Circadian Clock • Body temperature

  2. Sleep and the Brain • Sleep is controlled by many brain regions: • The hypothalamus is important in the control of NREM sleep

  3. Sleep and the brain • The pons is important in initiatingREM sleep • Neurons in the pons activate neurons in the visual region of the thalamus (rapid eye movements) as well as neurons in the cerebral cortex (dreams) • The pons also sends inhibitory signalsto the spinal cord causing temporary muscle paralysis

  4. Sleep and the brain

  5. How does sleep change with age? • Sleep patterns change during an individual’s life • Newborns sleep on average 16-18 hours/day • Children 3-5 years: 10-12 hours of sleep • Adulthood: 7-8 hours • Young children have a high arousal threshold, meaning they can sleep through very loud noises. • Elderly people experience increased sleep fragmentation (frequent arousals from sleep).

  6. how does rem sleep change with age? • The time spent in REM sleep changes throughout an individual’s life: • Newborns spend almost 50% of their total sleep time in REM sleep • At 2 years, REM sleep accounts for 20-25% of total sleep time. This remains constant throughout the remainder of life. • People with Alzheimer’s or Parkinson’s Disease have decreasing amounts of REM sleep as the disorder progresses

  7. Ave. hours of Sleep and % of REM sleep at different ages

  8. How much sleep do I need? • Individual sleep needs vary • Teenagers require about 9 hours of sleep to be as alert as possible when awake • Eight hours is optimal for most adults

  9. What is a circadian Clock? • An internal biological clock which regulates the timing for sleep in humans • It cycles with a 24.5 hour period • The ‘clock’ is located in the suprachiasmatic nucleus (SCN) of the hypothalamus in the brain

  10. How is it that our circadian clocks cycle on a 24.5 hour period but a day is 24 hours? …in other words, how does the body synch our internal clocks with the external clock?

  11. Entrainment of the circadian clock • The circadian clock is 24.5 hours but a day is 24 hours, therefore the clock must be entrained, or reset to match the day length. • The cue that synchronizes the internal biological clock to the environmental cycle is light • In absence of this cue, the circadian clock will follow it’s natural 24.5 hour rhythm

  12. Entrainment of the circadian clock • Light activates photoreceptors (nerve cells) on the retina of the eye • These cells then transmit electrical signals (APs) to neurons in SCN • The neurons at the SCN control several genes and neurochemicals that serve as biological “pacemakers”. • The regulation of these genes is what controls internal biological signals that our body interprets as ‘day’ or ‘night’

  13. Entrainment of the Circadian Clock • The release of melatonin, a hormone produced by the pineal gland is controlled by the circadian clock in the SCN • It’s levels naturally rise during the night and decline at dawn • Administering melatonin can produce changes in circadian rhythms • This is helpful for entraining rhythms in blind people • Melatonin is available as a non-prescription sleeping pill

  14. Rhythms: Body temperature • The cycle of body temperature is also controlled by the biological clock • Body temp is lowest at night and rises during the day • This fluctuation persists even in the absence of sleep

  15. Journal #3: Answer the following questions • What brain structure is responsible for controlling NREM sleep? • What brain structure is responsible for initiating REM sleep? Which other brain structures does this structure have connections with and what is the result of this? • How does the average time you sleep for and number of hours of REM sleep change throughout your life? • Do all people require the same amount of sleep? Explain. • In what part of your brain is the suprachiasmic nucleus located? • Why must the biological clock be entrained? • Explain how light entrains your biological clock. • What is melatonin, what does it do, what gland is responsible for it’s release, and what part of the brain controls it’s release. • How does body temperature vary throughout the day?

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