Week 9

• Circadian rhythms


  24-hour cycles that are part of the body’s internal clock, running in the background to carry out essential functions and processes.
• One of the most important and well-known circadian rhythms is the sleep-wake cycle.
• The term circadian comes from the Latin words for about a day
• To establish and maintain these rhythms, internal biological clocks interact with stimuli known as zeitgebers.
• (Zeit means “time” in German; geber means “to give”; hence these are “time givers.”).
• an internal for setting biological rhythms.

  Zeitgeber
• the most important zeitgeber for human beings.

  Light
• larks


  People who are most alert and productive in the morning have been referred to as
• Night people have been referred to as

  night owls
• Suprachiasmatic Nucleus (SCN)


  an area of the hypothalamus located above the optic chiasm;
• The SCN is active only during the day, this is true regardless of whether a species is diurnal (awake during the day), like monkeys, or nocturnal (awake at night), like rats.
• diurnal 


  (awake during the day),
• nocturnal


  (awake at night),
• The SCN helps animals distinguish between day and night, but other

  structures dictate whether an animal is nocturnal or diurnal in its behavior.
• Retinohypothalamic pathway


  it is a small branch of the optic nerve which is a pathway leading from the retina of the eye to the hypothalamus;
• Melanopsin


  a photopigment used by *non-image-forming (NIF) retinal cells, related to, but different from, the other photopigments involved in vision
• The SCN regulates waking and sleeping by controlling activity levels in other brain areas, including the pineal gland.
• The pineal gland releases the hormone melatonin.
• Melatonin 


  is a widespread chemical, found in nearly all animals— sponges are the only known exception—as well as in plants and bacteria.
• Cortisol 


  A hormone released by the adrenal glands that promotes arousal.
• beta wave


  a brain waveform having 15 to 20 cycles per second, associated with high levels of alertness during wakefulness.
• alpha wave 


  a brain waveform having 9 to12 cycles per second, associated with less alertness and more relaxation than beta activity during wakefulness.
• ultradian cycle


  a cycle that occurs several times in a single day
• non-REM sleep (NREM)


  A period of sleep characterized by slow, synchronous brain activity, reductions in heart rate, and muscle relaxation.
• Theta wave


  a brain waveform having 4 to 7 cycles per second found primarily in lighter stages of NREM sleep
• Melatonin


  one of the neurochemicals involved in the regulation of sleep patterns, drops dramatically at the onset of puberty, possibly contributing to age-related changes in sleep habits
• Jet lag


  a disruption of circadian rhythms due to crossing time zones.
• Suprachiasmatic Nucleus (SCN)


  responsible for maintaining circadian rhythms.
• Retinohypothalamic pathway


  provides light information necessary for the maintenance of circadian rhythms.
• REM dreams


  lengthy, complicated, vivid, and story like, providing us with the sense of firsthand experience with the events taking place.
• NREM dreams


  short episodes characterized by logical single images and a relative lack of emotion.
• When the content of a REM dream is especially upsetting, we refer to the

  experience as a nightmare (REM dream with frightening content).
• night terrors


  (NREM episode in which the individual is partially aroused, disoriented, frightened, and inconsolable)
• night terrors


  occurs during NREM, particularly during the first three hours of sleep.
• Acetylcholine


  -High during wakefulness and REM,

  -low during NREM
• Acetylcholine


  • Active in the pons and basal forebrain
• Acetylcholine (effect of antagonistsfor neurochemicals) 


  Decreased arousal and REM sleep
• Acetylcholine (effect of agonists for neurochemical) 


  Increased arousal and REM sleep
• Histamine


  High during wakefulness, low during NREM and REM
• Histamine


  • Active in the thalamus and hypothalamus