Biological Rhythms and Sleep

Periodic physiological fluctuations in the body. We are unaware of most biological rhythms, such as the rise and fall of hormones in the bloodstream, accelerated and decelerated cycles of brain activity, and highs and lows in body temperature, but they can influence our behaviour.

• Annual or seasonal cycles, such the migration of birds, the hibernation of bears, and the seasonal fluctuations of humans‘ eating habits.
• Twenty-eight day cycle, such as the female menstrual cycle that averages 28 days
• Twenty-four hour cycle, such as the sleep/wake cycle and temperature changes in the body.

Circadian Rhythms

• Daily behavioural or physiological cycle.  The term circadian comes for the Latin word circa, meaning “about” and dies, meaning “day.”
• Daily  circadian  rhythms  involve  the  sleep/wake  cycle,  body  and temperature,  blood pressure, and blood sugar level.
• Researchers  have  discovered  that  the  change  from  day  to  night  is monitored  by  the suprachiasmatic nucleus (SCN), a small structure in the brain that synchronizes its own rhythm with the daily cycle of light and dark based on input from the retina.
• Output  from  the  SCN  allows  the  hypothalamus  to  regulate  daily rhythms  such  as temperature and hunger and the reticular formation to regulate daily rhythms of sleep and wakefulness.

Desynchronizing the Biological Clock

• Biological clocks can become desynchronized, or thrown off their regular schedules.
• The jet lag you experienced when you flew from Vancouver to Halifax occurred because your body time was out of phase, or synchronization, with clock time. Jet lag is the result of two or more body rhythms being out of sync.

Resetting the Biological Clock

• Recently, Concordia  University  psychologists  Andreas Arvanitogiannis  and  Shimon Amir have found that circadian clock can be reset, mainly by the use of ultra-short light flashes.
• Melatonin, a hormone that is produced in greater quantities at night in humans, is also being studied for its possible effects in reducing jet lag.

Why Do We Need Sleep?

• The important benefits of sleep include restoration, adaptation, growth, and memory.
• Sleep is a fundamental mechanism for survival.
• Examining   the   evolutionary   basis   for   sleep, scientists   have   proposed that   sleep   restores, replenishes, and rebuilds our brains and bodies, which can become worn out or used by the day’s waking activities.
• In support of the restorative function of sleep, many of the body’s cells show increased production and reduced breakdown of proteins during deep sleep.
• Protein molecules are the building blocks needed for cell growth and for repair of damages from factors such as stress.  Also, some neuroscientists believe that sleep  gives  neurons  that  are  used while we are awake a chance to shut down and repair themselves.
• Without sleep, neurons might  become so  depleted  in energy or so  polluted by the byproducts of cellular activity that they begin to malfunction.
• Sleep may also be beneficial  to  physical  growth  and  increased  brain development  in  infants and children. For example, deep sleep coincides with the release of growth hormone in children.
• Sleep is also now thought to play an important role in the storage and maintenance of long-term memory. In one recent study, the stage of sleep called REM sleep (Rapid Eye movement sleep)was linked with the formation of emotional memories in humans.
• One possible explanation  is  that  during  sleep  the  cerebral  cortex  is  not busy  with  processing sensory input, active awareness, and motor functions.
• Therefore, it is free to conduct activities that strengthen memory  associations so  that  memories  formed  during  recent  waking  hours  can  be integrated into long-term memory storage.

The Effects of Chronic Sleep Deprivation

• An increasing number  of  research  studies  underscore  that  optimal performance  in enhancing by sleeping more than eight hours a night and reduced by sleeping less.
• Sleep deprivation can also affect decision making. A recent review of studies on the topic concluded that the following aspects of decision making are affected adversely by sleep deprivation:  dealing  with  the unexpected,  innovation,  revising  plans,  and  effective
• communications.

Sleep Deprivation in Adolescents and Older Adults

• This interest  focuses on  the belief that  many adolescents are  not getting enough  sleep, that there are physiological underpinnings to adolescents’ desires to stay up later at night and   sleep   longer   in   the morning,   and   that   these   findings   have   implications   for understanding when adolescents learn most effectively in school.
• Researchers found that older adolescents (16-18 yrs old) are often sleepier during the day than younger adolescents (13-15 yrs old).
• Sleep patterns also change as people age through the middle-adult (40s & 50s) and late- adult (60s and older) yrs. Many adults go to bed earlier at night and wake up earlier in the morning. Thus, a clear reversal occurs in the time at which individuals go to bed—later to bed as
• adolescents, earlier to bed in middle age.