Body Rhythms & Sleep

1. Body Rhythms&Sleep

2. Natural variations we experience daily in our psychological and physiological functioning • Fall into three main categories • Circadian Rhythms • Ultradian Rhythms • Infradian Rhythms Biological Rhythms

3. Circadian Rhythms • Any rhythmic change that occurs approximately once in a 24-hour cycle • Responsible for our arousal levels throughout the day. • Many of your processes like blood pressure, hormones, pain sensitivity along with sleep and wake cycles vary over the day • If time, watch the Cave Experiment from The Brain: Module 13 (6 min) • In the absence of time cues, the cycle period will become somewhat longer than 24 hours

5. The Body’s Clock • Suprachiasmatic nucleus (SCN) — cluster of neurons in the hypothalamus that governs the timing of circadian rhythms • Melatonin —hormone of the pineal gland that produces sleepiness

6. The Body’s Clock: How it works • Special photoreceptors in the retina regulate the effects of light on the body’s circadian rhythms • In response to morning light, signals from these special photoreceptors are relayed via the optic nerve to the suprachiasmatic nucleus. • In turn, the suprachiasmatic nucleus causes the pineal gland to reduce the production of melatonin, a hormone that causes sleepiness. • As blood levels of melatonin decrease, mental alertness increases. • Daily exposure to bright light, especially sunlight, helps keep the body’s circadian rhythms synchronized and operating on a 24-hour schedule.

7. How Melatonin works: • More melatonin = sleepy and reduce activity levels • highest levels between 1-3 AM • Less Melatonin = more alert and active • Body stops produced melatonin shortly before sunrise and sunlight suppresses melatonin levels throughout the day • Jet Lag – Since your body is still operating on the time you left from, your melatonin levels will be off causing a disruption in your circadian rhythms and making you mentally fatigued, depressed, irritable and have problems sleeping. • Night workers will always have some problems due to sunlight resetting their biological clock.

9. Biological Rhythms • Play “Can You Beat Jet Lag?” (6:44) - (Start at 16:00). • Segment #15 from Scientific American Frontiers: Video Collection for Introductory Psychology (2nd edition) • How light is used by the body to “reset” your biological clock.

10. Not a Morning Person? • Sleep Inertia - feeling of grogginess or impaired mental ability immediately following an abrupt awakening • Staying in bed until the last possible moment will only intensifydisorientation as you hustle to work. • Best way to treat it is to allow for more passage of time. • Set your alarm 15 minutes earlier and make it so you have to get up to turn it off. • Drink something with caffeine and sit near sunlight. • Read something or do meditation to get your brain engaged.

11. Ultradian Rhythms • Biological rhythms that occur more than once each day • Example: Cycling through the stages of sleep throughout the night, appetite

12. Infradian Rhythms • Biological rhythms that occur once a month or once a season • These rhythms are infrequent • Example: • Women’s menstrual cycle • bear’s winter hibernation

13. The Stages of Sleep

14. Why do We Sleep? • Restoration theory—body wears out during the day and sleep is necessary to put it back in shape • NREM sleep sees increases in the release of growth hormone, testosterone, prolactin. • REM sleep plays a role in rate of brain development that occurs in the early stages of the lifespan. • Allows neurons to repair themselves while pruning unused connections • Sleep consolidates memories – strengthening neural connections • Allows us to be better problem solvers the next day • Adaptive theory—sleep emerged in evolution to preserve energy and protect during the time of day when there is little value and considerable danger • Animals with few natural predators sleep the most while animals with many sleep less. • Hibernation occurs during the time of year most hazardous to the animal.

15. Electroencephalograph (EEG) • A machine that amplifies and records waves of electrical activity that sweep across the brain’s surface • Electrodes are placed on the person’s scalp to measure the waves • Used as a means to measure the stages of sleep

16. Electroencephalogram (EEG) • Electrodes placed on the scalp provide a record of the electrical activity of the brain • EEG recordings are a rough index of psychological states

17. EEG Waves of Wakefulness Alpha Waves: Awake but non-attentive Larger amplitude Beta Waves: Awake & attentive low amplitude fast, irregular

18. Onset of Sleep • Awake & alert, your brain produces small, fast brain waves called beta waves. • As you lay down and close your eyes, your brain's electrical activity gradually gears down generating slightly larger and slower alpha brain waves. • During drowsy, presleep stage you may experience vivid sensory phenomena called hypnagogic hallucinations. • Most common hallucination is that of falling which can produce a myoclonic jerk or sleep starts – involuntary muscle spasm of the whole body that jolts the person completely awake.

19. Stage 1 Sleep • Breathing is slowed. • Brain waves become irregular. • It is easy to wake the person, who will insist they are not asleep. • Lasts only a few minutes. • Familiar sounds fade away but your can regain alertness if something interrupts you. • Some imagery is common although no very strange or vivid.

20. Stages of Sleep

21. Stage 1

22. Stage 1

23. Stage 2 Sleep • Brain wave cycle slows. • Appearance of sleep spindles or brief bursts of brain activity and K complexes or large high-voltage spikes of brain activity that periodically occur. • Brain activity slows considerably and breathing becomes rhythmic. • Slight muscle twitches occur. • Brain waves begin to slowly switch from Theta waves to slower and larger delta waves.

24. Stage 2 K Complex

25. Stages 3 and 4 Sleep“Slow Wave Sleep” • Increase in delta waves (large & slow waves per second) • 20% = Stage 3. More than 50% = Stage 4. • First time through stage 4 is about 30 minutes and is where one gets rejuvenated • During the first stage 4 of sleep, heart rate, blood pressure and breathing drop to their lowest levels and it is very hard to wake up. • Sleepwalking occurs here. • People can "wake up" during stage 4 and do a simple task and not remember it.

26. Stage 4

27. 1 second Sleep stage 1 Sleep stage 2 Spindlers (bursts of activity) Sleep stage 4 Delta waves Stages of Sleep1-4Quick Review • Sleep stage 1: brief transition stage when first falling asleep • Stages 2 through 4 (slow-wave sleep): successively deeper stages of sleep • Slow Wave 3 & 4: Characterized by an increasing percentage of slow, irregular, high-amplitude delta waves

28. REM Sleep • N-REM (non-REM sleep) = Stages 1 - 4 • REM Sleep - Rapid eye movement as eyes move quickly back and forth • Most dreaming occurs in REM • muscle activity is suppressed to keep you acting them out. • REM Rebound - If denied REM sleep and then allowed a person will “Catch Up” on REM sleep and will increase their time in REM by 50%.

29. REM Sleep

30. REM: Paradoxical Sleep • One’s physiology is close to that of being awake but the brainstem blocks all muscle movement • Brain wave patterns are similar to when a person is awake • Visual and motor neurons in the brain fire like they do when you are awake. • Eyes dart back and forth and heart rate, blood pressure and respirations fluctuate up and down. • The first REM cycle lasts for 5 to 15 minutes. Each one gets longer as night goes on.

31. Stages of Sleep • Upon reaching stage 4 and after about 80 to 100 minutes of total sleep time, sleep lightens, returns through stages 3 and 2 • REM sleep emerges, characterized by EEG patterns that resemble beta waves of alert wakefulness • muscles most relaxed • rapid eye movements occur • dreams occur • Four or five sleep cycles occur in a typical night’s sleep; less time is spent in slow-wave, more is spent in REM

32. Typical Night’s Sleep

34. Sleep Changes through Life

35. Sleep Review • Play “Sleep: Brain Functions” (11:12) • Module #14 from The Brain: Teaching Modules (2nd edition). • Review of the stages of sleep. • What happens to animals that are not allowed to sleep? • What defines normal & abnormal sleep? • Categories of Sleep Disorders