Sleep and Biological Rhythms (Ch.14) Flashcards
Types of “Circa Rhythms”
- Circatidal (12 hrs)
- Circadian (24 hrs)
- Circalunar (30days)
- Circannual (one year)
Period:
The time interval separating one peak or trough from the next in a repeating cycle
Zeitgeber:
Time giver
- Circadian Rhythms (reoccurring naturally on a 24 hour clock) slightly are the result of an
Endogenous clock (a clock from within)
Daily Rhythms persist in..
constant conditions
Rythms develop normally in the absence of…
external cycles (innate)
Tau:
- Tau varies across and within species in the same environment
- Tau can be selected by breeding altered by gene mutations and eliminated by gene knockouts
Jean deMairan 1729 identified the first circadian rhythm in the Mimosa Plant using …
temporal isolation
- Adaptive Significance of Circadian clocks: External coordination and anticipation to:
- Geographic Stimuli (light, temp)
- Biological stimuli (food resources, predators, mates)
Do circadian clocks contribute to fitness in Natural Habitats?
-SCN ablated animals were in burrows at night however they were active which increase their predation
Entrainment phase
Animals display different endogenous(originating from within) periods that don’t exactly match the environmental light dark cycle
Entrainment Hypothesis
Entrainment is achieved by daily adjustment of rhythm phase, to offset the difference between τ and T.
- Squirles see light for only a few seconds every 3 to 4 days
Retinohypothalmic Tract:
- Intrinsically photosensitive retinal ganglion cells
- Axons that make up the RHT do not originate from rods and cones
Entrainment Pathway
- Light enters the eyes through the rods and cones and Speacialized ganglion cells (containing melanopsin)
- Then go through the Retinohypothalaamic tract to thalamus to form the vision
(END OF ENTRAINMENT)
Evidence that the SCN are an endogenous circadian clock
- Lesions of the SCN eliminate rhythmicity
- Electrical or chemical stimulation of the SCN induces phase shifts
- SCN neurons oscillate (move back and forth at a normal speed)
- SCN transplants can restore rhythms after SCN lessons (with the period of the donor)
What other Stimuli contribute to entrainment besides light?
- Arousal
- Exercise
- Drugs
- > these stimuli exert their influences on the SCN via another neural pathway
Chronotype: Night owls and early birds
-Between ages 10 and 40 men tend to be later risers than females
Why Study Circadian Rhythms?: Human Performanc and Societal cost
Physical and cognitive capacities vary throughout the day (shift work, travel, education, sports)
- Need of job, demand for services (firefighter)
- Problemed areas: performance and productivity, safety, health
Why Study Circadian Rhythms?: Medicine
Rhythms are important for both diagnosis and treatment
Why Study Circadian Rhythms?: Psychopathology
Disruption of circadian timing implicated in sleep and affective disorders
Shift work and Productivity
- The greater you work the greater your output, BUT for many jobs productivity per hour of work is lower on 10-12 compared to 8
- Leads to increased risk of accident
Health Problems of Shift Workers
- Sleep and Vigilance
- Cardiovascular System (50% increase in risk - increases with years of exposure to shift work)
- Gastrointestinal System - Significant increase for GI disease (e.g. ulcers)
- Hormonal and reproductive system
- Anxiety, depression, substance use