Week 8: Sleep and Biorhythms Flashcards
Rhythm
Cyclic variation in a process over time
Circadian rhythm
Repeats approximately every 24 hours; sleep
Infradian rhythm
Repeats between 24 hours and one year; mating, breeding, migration
Ultradian
Repeats in less than 24 hours; eating/hunger
Bunker study
Method: secluded humans in a bunker with no access to light cues or clocks. Limit sense of time
Findings: Still followed a sleep cycle pattern similar to normal (about 25 hour cycle)
Suggestion: Cycles/rhythms are biologically hardwired, and can be adapted by external cues
Endogenous/free-running rhythms
Rhythms that exist even in the absence of cues. Can be changed by cue input.
Rhythm study in animals
Method: Submit animals either to constant light or constant dark. Observe activity patterns
Findings: In nocturnal animals, activity was heightened in constant dark and lessened in constant light. Vis versa for non-nocturnal animals. All animals still kept cycles, but they were altered
Supports notion of endogenous rhythms
Drosophilia studies (fruit flies)
Done in the 70s. Method: mutate the PER gene in flies and observe behavior
Findings: Disruption of gene led to disruption of rhythms
Suggestion: rare case where a process is directly related to one gene (PER).
Evidence supporting PER control of rhythms
Expression of PER varies with different levels of activity
Transplants of non-mutated PER genes would restore damaged cycles
Clock genes
PER and CRY (among others)
Clock gene circuit
Clock + Bmal1 -> CRY + PER -> inhibition
Internal clock and Bmal1 produces CRY and PER over time, which combine to make an inhibition factor on the clock. Over time CRY and PER levels decrease.
Self-limiting system, which creates the cyclic/wave pattern
Delayed sleep phase disorder
Habitual strong pressure to sleep and wake later than normal. Affects 1-10% of the pop. Related to CRY1
Familial advanced sleep disorder
Wake up early and go to bed late. Inheritable from genetics. Related to PER2
Suprachiasmatic nucleus (SCN)
Area of the brain in the hypothalamic nucleus located close to the optic chiasm. Aligns all the rhythm pattern in the body with each other. Designed/positioned to receive light as a cue to function (optic location). Will rhythmically fire even when isolated from cues
Affects of Lesion to SCN
Activity rhythm loss. Measured by watching wheel running behavior/patterns in rodents. Those with lesions had sporadic running patterns. Transplanting healthy SCN restores pattern, but of the host animal, not the receiving animal
Light sets rhythm
Retinal ganglion cells (RGNs) are reacting to light and producing melanopsin, which enacts rhythms. Cause of biologically set rhythms
Ways to improve sleep
Light exposure and activity early in the day, melatonin late in the day, no caffeine late in the day
Melatonin
Creates physiological pressure for sleep. Light inhibits production (less light, less inhibition, more production, more eepy). Produced by the pineal gland. Affects tissues across the body
Affect of individual light sensitivity
Melatonin production can vary, and thus determine the needed environment for beneficial sleep. Those with low sensitivity might have more melatonin production
Effects of electronics on sleep
More light leads to more sleep disruption via less melatonin production. Leads to poor sleep and mental health problems
Adenosine
Creates sleep pressure; increases during day, decreases during night. Weakened by caffeine
Cortisol
The stress hormone, involved in arousal. Begins rising before we wake up in the morning. Increased levels cause arousal, hence why you can’t sleep after stressful events
Exercise affecting sleep
Creates arousal, which inhibits sleep. Exercise early, sleep early; vis versa
Chronotype
Natural wake/sleep cycle predisposition. Influenced by age, gender, etc. Kids wake earlier than adults, women earlier than men
Early bird sleep type
“Morningness”. Associated with higher academic performance. Typically agreeable and conscientious
