PSYC 460 -- Notes on Sleep (Part III) -- Dr. King

Slide 1: Biological Rhythms

Slide 2: We are NOT talking about biorhythms, for which there is no credible
scientific evidence or plausible biological mechanism! 

Slide 3: We ARE talking about daily rest-activity cycles and factors that might
result in jet lag. 

Slide 4: Also, seasonal rhythms and longer.

Slide 5: Here's basically how it works... 
   A. Zeitgebers ("time givers")
   B. Clock (oscillator)
   C. Rhythmic behaviors

Slide 6: Zeitgebers 
   A. the day-night cycle (sunrise)
   B. the tides
   C. alarm clocks

Slide 7: Circadian Rhythms 
   A. circadian = "about a day"
      1. the primary (but not the only) clock for circadian rhythms is in the 
         suprachiasmatic nucleus of the hypothalamus 
      2. the SCN receives input from a special light-sensitive ganglion cell 
         in the retina, which contains a photopigment called melanopsin 

Slide 8: Circadian Rhythms 
   A. retinal ganglion cells 
   B. 2-DG autoradiographs of the SCN 

Slide 9: Circadian Rhythms 
   A. the SCN only does the timing; it does not control the behaviors 
   B. firing rates of SCN neurons have a distinct circadian periodicity 
   C. the rhythm is "built-in"
   D. appears to involve protein synthesis by about 7 different genes 

Slide 10: Circadian Rhythms 
   A. notice these cells are out of phase (in a petri dish)
   B. normally, the cells would make dendrite-to-dendrite synapses in order to
      synchronize their activity 
   C. SCN times rhythms for sleep/waking, eating/drinking, body temperature,
      hormones, etc. 

Slide 11: Circadian Rhythms 
   A. lesions of the SCN destroy the periodicity of these behaviors ...
   B. while leaving normal amounts of the behaviors 

Slide 12: Circadian Rhythms 
   A. free-running rhythms - in the absence of environmental cues, most
      circadian rhythms tend to run a little longer than 24 hrs. 
   B. in nature circadian rhythms are "entrained" to environmental cues that
      have a 24-hr. period 

Slide 13: free-running rhythms 

Slide 14: Circadian Rhythms 
   A. the SCN controls the rhythm of the sleep-waking cycle via a connection to
      the dorsomedial nuc. of the hypothalamus (DMH) 
   B. the DMH connects to the ventrolateral preoptic area (VLPOA), the main
      sleep producing area in the hypothalamus

Slide 15: Circadian Rhythms 

Slide 16: It ain't easy being a circadian rhythm these days (light pollution)

Slide 17: It ain't easy being a circadian rhythm these days (jet lag)

Slide 18: It ain't easy being a circadian rhythm these days (shift work)

Slide 19: Seasonal Rhythms 
   A. the pineal gland and melatonin 
   B. melatonin is secreted from the pineal gland during the night 
      1. regulated by input from the SCN via... 
         a. paraventricular nuc. of the hypothalamus 
         b. sympathetic nervous system 

Slide 20: Seasonal Rhythms (illustrations of the anatomy)

Slide 21: Seasonal Rhythms 
   A. during winter months when the nights are longer, more melatonin is
      secreted, and animals go into their winter phase of the behavioral cycle
   B. something similar may happen in humans, resulting in: 
      1. weight gain during the winter 
      2. seasonal affective disorder 

Slide 22: Seasonal Rhythms 
   A. control of seasonal cycles in hormone secretion 
      1. retino-hypothalamic tract - glutamate
      2. activates the SCN (suprachiasmatic nuc.)
      3. via the paraventricular nuc. and sympathetic nervous system, stimulates
         the release of melatonin from the pineal gland - norepinephrine
      4. influences prolactin secretion from the anterior pituitary gland
      5. and gonadotropic releasing hormone from the hypothalamus

Slide 23: The End of Sleep