MODULE ONE: INTRODUCTION TO BIOLOGICAL RHYTMS AND SLEEP Flashcards
what is chronobiology?
the study of biological rhythms in hours, days, months, and years
chronos means __
time
bios means __
life
logos means __
study
what are circadian rhythms?
rhythms that are controlled by internal 24 hour biological clocks and synchronize animal behaviour and physiology
what is a biological rhythm?
any biological process that repeats at regular intervals
what 2 domains are rhythms described in?
time and frequency
describe the time domain of rhythms
rhythm has a period
what is a period?
the time required to complete a full cycle
on a sinusoidal wave, measuring from crest to crest would be considered a ___?
period
describe the frequency domain of rhythms
the reciprocal of a period
what is the reciprocal of a period (frequency)? what is it measured in?
cycles per unit time ; Hz
what can account for diversities in biological periodicities/rhythms? (2)
external stimuli or intrinsic timing devices
what are the 3 types of rhythms based on their periods?
ultradian
daily
infradian
ultradian rhythms have periods of…
less than 24hrs
daily rhythms have periods of..
about 24 hours
infradian rhythms have periods of…
greater than 24hrs
what are the 4 types of circa rhythms within the environment?
circatidal
circadian
circalunar
circannual
what are circatidal rhythms? estimate their period
ultradian rhythms that match the tides
12.5hrs
what are circadian rhythms? estimate their period
the daily rhythm that matches the solar day
24hrs
what are circalunar rhythms? estimate their period
infradian rhythms that match the lunar month
29.5 days
what are circannual rhythms? estimate their period
infradian rhythms that match the solar year
365 days
circa rhythms are unique in 2 ways, what are they?
- they approximate the periodicity of a major geophysical and environmental cycle
- they can persist for many cycles even without their matching geophysical cycle
rhythms that persist in the absence of environmental cycles reflect what 2 implications?
- they must be generated by internal timekeeping devices that runs similarly to its corresponding environmental cycle
- environmental stimuli modify the internal clock to be synchronized to the outside world
what is entrainment?
the process of achieving synchronization
who coined the term circadian and emphasized the mathematical techniques to quantify parameters found in daily rhythms?
Franz Halberg
Franz Halberg’s graphs demonstrate what?
how much of the biochemistry and physiology of mice and humans exert in 24hrs
what can be said about the different rhythms seen in Franz Halberg’s graphs fo daily rhythms
they rise and fall at different times of the day
true or false: circadian rhythms are daily rhythms but not all daily rhythms are circadian
true
what must a daily rhythm have or do in order to be considered circadian?
must persist in the absence of 24-hour environmental cycles
who noticed plants followed the sun as they open and close their leaves in synchrony with day/night cycle?
Jean Jacques d’Orous de Marien
how did Jean come to his observation?
stored a plant in the closet with no light but still observed the opening and closing of leaves
who continued Jean’s work and demonstrated the same rhythm persists in constant temperature?
Duhamel du Monceau
who continued Jean’s work and used a cave as a shield?
Augustin de Candolle
what did Candolle observe?
the daily rhythm of the leaf was not exactly 24 hours because it was shorter than
who demonstrated time memory in honeybees?
August Forel
zeitgedachnis is german for?
time memory
Who demonstrated that honeybees can learn and remember time of day in deep salt mines but only if the a meal time occurs at the same time everyday in a 24 hour cycle?
Beling
Renner trained bees to find food on NYC time everyday at noon but when they brought them to California the bees flew out at the wrong time, why?
the bees were jetlagged
what is jetlag?
occurs when crossing multiple time zones very quickly and circadian clocks lag behind the transition
Renner’s observations showed what?
bees use an internal representation of time of day to decide when to forage and do not use local time cues
Carl Linnaeus has 3 flower categories, what are they?
meteorici
tropici
aequnictales
meteorci flowers open..
according to the weather
tropici flowers open..
according to the changing hours of daylight
aequinoctales flowers open..
at a specific hour of they day and close up at a specific hour
who invented the kymograph to record pressure or motion
carl ludwig
what was the kymograph?
a revolving drum wrapped around with paper and a stylus that can move up and down
who was interessted in sources of spontaneous behaviours that occur in the absence of environmental stimuli
Ritcher
how did Ritcher measure rat movement?
in a stationary cage on a rotating drum that was attached to a kymograph
what kind of behaviours were observed and exhibited rhythmically in a range of hours and days
moving, eating, and drinking
how were ink bars produced on the kymograph?
every rotation of the wheel open and closed a switch that would cause a 5V pulse and caused pen deflections
what is an actogram?
the preferred method to visualize circadian rhythm activity
what is it called when there is activity time drift in behaviour or physiological process?
free run
what is the issue with just using a pen and ink chart recorders to acquire an actogram?
there are no numbers and it requires further analyses
what is significant about using computerized data collection?
colours are used to represent data and create a heat map to reflect activity in each cell
what is the bivariate plotting format?
where the magnitude of each data point is plotted on the y-axis and the time of each data point is on the x-axis
true or false: information can be averaged across days and variability can be measured using computer data collection
true
what kind of information can be collected using computerized data collection? (3)
degree of nocturnality
range of variation of activity
shape of the waveform
what is beneficial about performing multiple measures over days/weeks rather than just a day?
allows manipulation and demonstration of circadian rhythms free run and drift
tau is another word for?
period
a free-running tau has a formula of what?
24hrs- (drift hours/#days it took to occur)
what is a subjective day?
when the animal acts as if it is day
what is subjective night?
when the animal acts as if its night
alpha stands for
active phase
pho stands for
rest phase
free running is:
a rhythm that persists in a time-free
what does it mean for a rhythm to be entrained?
it is synchronized to an external time cue
define Zeitgeber
any periodic stimulus that can entrain a circadian rhythm
what is a phase?
a position or point in a cycle
what are the 2 kinds of phases?
active
rest
what is acrophase?
the peak of a cosine function fit to a time series
define the amplitude of a sinusoidal wave
the difference between the peak and the trough of a rhythm or difference between a peak and the mean of the rhythm
define phase differences
difference between 2 time phases
what is a phase angle difference?
when the data is expressed in angular degrees rather than minutes
what is a photoperiod?
the daily light period
what is a scotoperiod
the daily dark period
how can one determine the validity of a curve
how closely the raw data corresponds to a sine wave
having a square-wave component in a circadian rhythm’s shape means what
it has been entrained to a 24hr light/dark cycle
in a study where subjects were kept in temporary isolation/in constant routine, after the first 20 days what was removed?
time of day cues
what was the observation of the temporary isolation experiment when the time of day cues was removed?
that subjects went to bed 2 hours later each day
the constant routine protocol and forced desynchrony yielded what?
rhythms estimated closer to 24 hours
what is the goal of the constant routine method?
to measure circadian rhythms of physiological variables in the absence of environmental and behavioural cues
subjects that stay in bed for 1-2 days in constant dim light with small isocaloric meals provided at regular intervals are being studied using what method?
constant routine method
the constant routine method brought attention to what?
3 types of daily rhythms that can be identified as circadian
what are the 3 types of daily rhythms that can be characterized as circadian rhythms?
- sleep dependent
- sleep-independent
- rhythms that persist in constant routine
what kind of rhythms are involved in sleep-dependent rhythms?
blood levels of growth hormone and prolactin
how /why are blood levels of growth hormone and prolactin considered sleep-dependent?
they are typically high at night and will not occur if sleep is prevented
what kind of rhythms are involved in sleep-independent rhythms?
blood levels of melatonin
how/why are blood levels of melatonin considered to be sleep-independent?
melatonin is synthesized and secreted at night via the pineal gland and is unaffected by sleep deprivation
are blood levels of growth hormone and prolactin indirectly or directly controlled by the circadian clock?
indirectly; is secondary to sleep/wake cycle
are plasma melatonin levels directly or indirectly controlled by the circadian clock?
directly
what kind of rhythms persist in the constant routine?
bodily temperature
how/why is bodily temperature considered a rhythm that persists in constant routine?
it rises in the day and falls at night
persists in subjects kept awake in constant routine or during a prolonged time of sleep
describe body temperature’s relationship with the circadian clock and the sleep/wake cycle
it is jointly controlled by the circadian clock and directly affected by sleep/wake cycle effects
for every 10 degree centigrade how are biological reaction rates altered?
they double in speed or decrease by half
true or false: biological reactions can violate the rate-temperature principle
false
what is required of a clock mechanism in order for it to tell accurate time across a range of temperatures?
temperature compensation
a temperature compensation model says that as tissue temperature rises, the clock mechanism speeds up. describe the proposed second mechanism
the increasing tissue temperature also increases an inhibitory mechanism output to counter balance the clock speed increase
because the temperature mechanism is still unknown, why might there be biological plausibility?
no known mechanism for a reported phenomenon can be viewed as skeptical
what does it mean for a mechanism to be endogenous?
it is internal to the organism
what does it mean for a mechanism to be innate?
it is genetically determined and does not require exposure to 24hr environmental time cues
in the 1930s the biological concept had not been examined. what was rhythm compared to instead?
memory established by experience
who settled the debate of innate vs acquired in terms of circadian rhythms?
Irwin Bunning
how did Irwin Bunning come to the conclusion that circadian rhythms are innate?
bred fruitflies in constant light for 30 generations where they did not experience circadian rhythms (disorganized)
moved the 31st generation in constant dark and then exerted normal circadian rhythms, even never have exhibited the 24 hour light/dark cycle
list the 6 observations that support the biological clock concept as being endogenous, innate, and genetically specified
rhythms develop normally in the absence of external stimuli
the circadian periodicity can differ between species in the same environment
tau differs within species of the same environment
tau can be selected by breeding
tau can be altered by gene mutations and eliminated by gene knockouts
tau changes with age and internal hormonal state
list the 10 reasons circadian rhythms should be studied
- physiological regulation and associated motivational states
- research design
- understanding how time is represented in the brain
- behavioural ecology
- human performance and social cost
- sleep disorders
- psychopathology
- aging/dementia
- medicine
- intrinsic interest
