sleep

• Sleep


  A normal, reversible, recurrent state of reduced responsiveness to external stimulation accompanied by complex and predictable changes in physiology
• Sleep


  • It is a basic human need and is essential for good health, good quality of life and performing well during the day
  • In medical terms, it is a complex biological process that helps you process new information, stay healthy, and feel rested
  • During sleep, the noticeable changes in brain electrical activity are due to the brain's billions of nerve cells physically repairing themselves
• Basic theories of sleep

  • Inactivity theory
  • Energy conservation theory
  • Restoration theory
  • Brain plasticity theory
• Inactivity theory


  Based on the concept of evolutionary pressure where creatures inactive at night were less likely to die from predation or injury in the dark, thus creating an evolutionary and reproductive benefit to being inactive at night
• Energy conservation theory


  The main function of sleep is to reduce a person's energy demand during part of the day and night when it is least efficient to hunt for food. Body temperature and calorie needs decline during sleep compared to an awake state.
• Restoration theory


  Sleep promotes tissue repair and restoration. During non-REM sleep, bodily tissues mend and regenerate, whereas during REM sleep, brain tissue repairs.
• Brain plasticity theory


  Sleep improves our brain plasticity, which is the structure and organization of the brain. Sleep is necessary for neural reorganization and growth of the brain's structure and function.
• Caffeine intake can block adenosine (a naturally occurring substance that relaxes and dilates blood vessels) activities in the brain, keeping us attentive. The body has an opportunity to eliminate adenosine from circulation while sleeping, which makes us feel more attentive when we wake up.
• Sleep


  A time of tranquility when we set aside the tensions of the day and spend the night in uneventful slumber
• The brain is quite active during the night, producing electrical discharges with systematic, wavelike patterns that change in height and speed in regular sequences
• There is also significant physical activity in muscle and eye movements during sleep
• Sleep stages


  1. Stage 1

  2. Stage 2

  3. Stage 3

  4. Stage 4

  5. REM sleep
• Stage 1 sleep


  Characterized by relatively rapid, low-amplitude brain waves, a stage of transition between wakefulness and sleep
• Stage 1 sleep


  • Brain produces high amplitude alpha waves and begins to produce theta waves
  • As the waves slow down, the brain goes into a deeper sleep
  • Alpha waves are the highest frequency, explaining why people can be easily awoken
• Stage 2 sleep


  Characterized by a slower, more regular wave pattern, with momentary interruptions of sharply pointed, spiky waves called sleep spindles
• Stage 2 sleep


  • Body temperature drops, eye movements stop
  • Brain produces theta waves and bursts of rapid, rhythmic brain wave activity known as sleep spindles
  • Also characterized by k-complexes, high amplitude patterns of brain activity
• Stage 3 and 4 sleep


  Brain waves become slower, with higher peaks and lower valleys in the wave pattern
• Stage 3 and 4 sleep


  • People are least responsive to outside stimulation
  • Stage 4 sleep is most likely to occur during the early part of the night
  • Stages 3 and 4 dominate the first half of the night
• Stage 3 and 4 sleep


  Referred to as "slow wave sleep", due to the presence of delta waves, or slow brain waves
• Stage 3 and 4 sleep

  • Sleepwalking and night terrors are a unique characteristic
  • Human growth hormone (HGH) is released, which works to restore and rebuild the body and muscles
• Non-REM sleep


  Marked by a reduction of physiological activity as bodily functions slow down
• Non-REM sleep


  • Consists of three phases: N1, N2, and N3
  • Electrical activity in the brain slows, growth hormone secretion occurs, and there is a decrease in muscle activity, heart rate, respiration, and oxygen consumption
• REM sleep


  Marked by intense brain activity and is a much more active period of sleep than non-REM
• REM sleep


  • Heavily regulated by the brainstem
  • Occurs after the brain passes through stages one, two, and three, and typically occurs approximately every 90 minutes
  • Brain activity increases, voluntary muscles are inhibited, and rapid eye movements and dreams occur
• Circadian rhythm


  Our 24-hour clock that operates as our sleep/wake cycle
• Circadian rhythm


  • Located in the superchiasmatic nucleus (SCN) in the hypothalamus
  • Controls the production of melatonin, a hormone that makes you sleepy, by receiving information about incoming light from the eyes
  • When there is less light (like at night), the SCN tells the brain to make more melatonin so you get drowsy and are able to fall asleep. After a night's rest, melatonin levels will drop, and you will be awake for the day