Biological Rhythms and Biological Clocks Flashcards
Biological rhythms
Any biological processes that repeat themselves at regular intervals
What is the name for rhythms «_space;24 hours?
Ultradian
What is the name for rhythms ~= 24 hours?
Daily
What is the name for rhythms»_space; 24 hours?
Infradian
What are the 4 “circa” rhythms?
- Circadian
- Circatidal
- Circalunar
- Circannual
What is the length of circadian rhythms?
24 hours
What is the length of circatidal rhythms?
12.5 hours
What is the length of circalunar rhythms?
29.5 days
What is the length of circannual rhythms?
~ 1 year
Is a circatidal rhythm ultradian or infradian?
Ultradian
Is a circalunar rhythm ultradian or infradian?
Infradian
Is a circannual rhythm ultradian or infradian?
Infradian
In the absence of external environmental cycles, the fact that circa rhythms persist has what 2 implications?
- That the rhythm must be generated by an internal, endogenous timekeeping device
- Signals from the environment somehow impact the biological clock, keeping it synced to the environmental cycle
How is it determined whether a daily rhythm is also circadian?
It must persist without ~ 24 hour environmental cycles (like light/dark)
Period (tau)
Duration of a cycle (equal to the wavelength)
Phase (phi)
A point on the cycle
How are the daily active and rest phases abbreviated?
Alpha and rho
Amplitude
The difference between the peak and trough of a rhythm, or between the peak and mean of the rhythm
Phase difference (psi)
The difference in time between two phases
Zeitgeber
Any periodic stimulus that can entrain a circadian rhythm
Zeitgeber time
External time (usually 24 hours)
Photoperiod
Duration of lights on
Scotoperiod
Duration of lights off
Are circadian rhythms “innate”? Why or why not?
Yes, because they do not require exposure to an environmental cycle in order to develop
What are two characteristics of “circa” rhythms?
- Under natural conditions, they are synchronized to major geophysical cycles in the environment
- Under artificial conditions, they persist within a period that approximates that of the corresponding geophysical environment
What is the name for animals that are primarily day active?
Diurnal
What is the name for animals that are primarily night active?
Nocturnal
What is the name for animals that are primarily dawn-and-dusk active?
Crepuscular
Oscillator
A device that produces a rhythm
Who coined the word “circadian”?
Franz Halberg
What are the possible explanations for the early appearance of circadian clocks?
- The need to shield certain biochemical processes from ionizing solar radiation
- Coordinating the activity of cellular antioxidant mechanisms with daily metabolic cycles
- The need to separate incompatible biochemical processes
What are the two primary functions of circadian clocks?
- Coordination of the organism with the outside work
- Coordination of internal biochemical and physiological processes
What type of organisms typically lack circadian rhythms of behaviour and sometimes lack circadian rhythms of gene expression?
Caverniculus organisms (cave dwelling)
Zeitgedächtnis
Time memory
Homeostasis
The regulation of vital physiological functions within certain optimal limits
What is the evidence that the source of circadian rhythms is endogenous and innate?
- Circadian rhythms persist in constant conditions, with a period usually slightly different from 24 hours
- Rhythms develop normally in the absence of external cycles
- Period differs within AND between species in same environment
- Period can be selected by breeding, altered by gene mutations, eliminated by gene knockout
- Period changes with age and internal hormonal state
What are the reasons for studying circadian rhythms?
- Understanding motivation
- Research design
- Neurobiology of time
- Behavioural ecology
- Shiftwork effects and solutions
- Sleep disorders
- Psychopathology
- Aging and dementia
- Medicine
- Interest
In IMAGE 1, what does each row represent?
A different variable
In IMAGE 1, what do the shaded areas represent?
Nighttime hours
In IMAGE 1, what does a dot on a horizontal line represent?
The time of day when the rhythm reaches its peak value
In IMAGE 1, what does the bar represent?
The standard deviation of the daily peak
In IMAGE 2, what is the chart called?
An actogram
In IMAGE 2, what does each line represent?
48 consecutive hours
Explain IMAGE 3
In the first 20 days, the subject is aware of time cues and goes to sleep at the same time each day, after the cues are removed (after day 21), their bedtime drifts by approx. 1.3 hours each day
