Test 1 Review Flashcards
what are biological clocks used for?
predict events that occur at regular intervals and anticipate change
what is an example of social adaptation to rhythms?
getting up for school/work at the same time every day regardless of changes in sunrise/sunset times in different locations throughout the year
what is a possible explanation for the development of clocks in organisms?
escaping from UV rays that damage DNA while still using light for energy
what is the major external synchronizer for marine animals?
tides, therefore moon phases
what are examples of a temporal program?
gonyaulax float during the day to collect light for photosynthesis, in the evening they sink down into the water column to fix nitrogen where they glow/sparkle; crassaculae (desert plants) separate photosynthesis and carbon fixation processes into day and night so they can safely open stomata without losing water; human hormones fluctuate based on sleep/wake cycle
what human hormones peak during the day and fall at night?
VLPO, adenosine, hypocretin
what human hormones peak at night and fall during the day?
GH, melatonin
how long is an ultradian rhythm?
how long is an infradian rhythm?
> 28 hours
what kinds of laboratory results support the idea of physiological clock mechanisms?
organisms maintaining rhythmic free running periods during DD laboratory conditions (mouse, hamster), organisms with clock mutations having arrhythmic free running periods
what are examples of biological clocks being used for orientation and/or migration?
bees use position of sun to communicate location of food sources to other bees and use internal clock to calculate locations at different hours of the day, amphipods use clocks to escape from predators, migratory birds use sun/stars for navigation, monarch butterflies follow directions of UV light
what are examples of biological clocks being used for reproduction/social behaviour?
coral populations all mass reproduce at one time, cashew plants reproduce annually, nocturnal cactus only blooms one night per year
how is sleep regulated? (what kind of clock)
seasonal
when does morning/evening preference develop and how does it differ between sexes?
puberty, females tend to prefer evening
how is time perceived?
an internal clock that anticipates irregular changes while assuming a 24 hour period
who first recorded daily rhythms?
Androsthenes
what did de Mairan record?
regular opening and closing of mimosa leaves in absence of LD cycle
what did de Candolle record?
plants are rhythmic without LD cycles but their rhythms are not exactly 24 hours
what did Linnaeus record?
flower clock (GAYYYYYYY)
what did Stoppel record? (fuck her)
bean plants daily leaf movement cycle stopped in mine shaft, so factor x must also affect rhythmicity
what did Kalmur record?
fruit fly eclosion is rhythmic, metabolism can be stopped and eclosion can be delayed by exposing flies to pure helium environment (delay is amount of time spent in helium)
what did Bunning record?
photoperiodism, drosophila become arrhythmic in LL cycle but resume rhythmicity in DD cycle, innateness (temp changes affect eclosion; lower = slower (delays))
what did Frisch record?
honey bees remember time of day they encountered food`
what did Kramer record?
birds use sun compass orientation (internal clock + sun position) to navigate during migration
what did Pittendrigh record?
organisms internal clocks anticipate changes in environment and so are affected by temperature through compensation for temp changes
what did Aschoff record?
emotions of humans throughout the day is rhythmic
what is tau?
length of endogenous rhythm
what is zeitgeber?
external time synchronizer
what is circadian time?
inner day/night cycle
what is phase shift?
rapid change in oscillation from one phase to another
what is phase angle difference?
difference between points from inner cycle and outer cycle
what is Q10=1?
rate of reaction changes by one unit with every 10 degree temp change
what is the perch behaviour of sparrows in LD12:12 and DD?
begin activity in subjective day CT0, in LD12:12 cycle sparrows synchronize (are diurnal), in DD they shift right (longer than 24 hours)
what is the activity of hamsters in LD12:12?
assume winter physiology, reproduce slower, internal rhythm shortened
what is entrainment?
when free running period does not equal environment, it is adjusted
what is masking?
when social zeitgeber rapidly changes but inner cycle adjusts slowly e.x. jet lag
what are two ways entrainment can occur?
change period (tau), reset phase every day
what are Aschoff’s rules?
- when light intensity increases, tau in nocturnal animals increases, tau in diurnal animals decreases
- tau in LL > tau in DD in nocturnal, tau in LL rest in LL in diurnal, rest > activity in LL for nocturnal
- tau 24 hours in diurnal
what is the behaviour of mice in LD12:12, DD, LD12:14, and LD12:10?
LD12:12 runs in dark i.e. subjective night, DD running length increases tau is close to 24 hours, LD12:14 delays cycle to synchronize, LD12:10 tau is shorter from LD12:14 so mouse now behaves like diurnal animal
what is relative coordination?
when periods of inner cycle and zeitgeber are too different for entrainment to occur
what is parametric entrainment?
entrainment that involves qualities of light
what is nonparametric entrainment?
entrainment based on presence or absence of light, accomplished through daily phase shift
what do phase response curves show?
relationships of delays or advances caused by pulses of light
what are CT0, CT12?
CT0 beginning of subjective day, CT12 beginning of subjective night
what are the effects of light pulses at CT0-12, CT12-18, CT18-0?
CT0-12 no effects, CT12-18 phase delays, CT18-0 phase advances
what are the effects of light pulses in the forbidden zone?
no entrainment, cycle is just interrupted
what is the phase angle difference equation?
delta phi = tau - T
how can phase angle of entrainment be altered?
changing circadian period (light pulses in delay or advance zones), changing zeitgeber period (lab only), changing shape of PRC, changing sensitivity of system to zeitgeber, masking/after effects, phase shifting to nonphotic stimuli
what are nonphotic stimuli?
everything that is not light changes/pulses, including dark pulses which are not just absence of light, have greatest effects when introduced at unexpected times
what is are the effects of triazolam?
mimics effects of dark pulses, makes hamsters run like crazy when they have a wheel, no effect on activity when they don’t have a wheel
what are the effects of dark pulses?
cause phase shifts in subjective day, requires behavioural activation/arousal
what are the effects of introduction of a novel running wheel?
mimics effects of dark pulses/triazolam
how can stimuli interact?
- shift by one stimulus moves clock such that second stimulus falls at a new CT
- in rodents, simultaneous arousal can reduce effects of light induced shift
- in rodents, nonphotic shift followed by photic shift negates effects of light pulse
- changes in light intensity can cause behavioural arousal
what is an example of nonphotic entrainment?
insect vector of chagas disease can be entrained using chicken pulse
what did Eskin discover?
brain site responsible for entrainment of sparrow clock
what did Gaston discover?
pineal gland important for rhythmicity (avian)
what did Zimmerman discover?
rhythmicity transferrable via pineal gland grafting (avian)
what did Takahashi discover?
SCN important for rhythmicity, pineal gland releases melatonin for sleep (avian)
what did Cassone discover?
norepinephrine can entrain the pineal gland rhythm, melatonin causes phase shifts in the SCN clock
what is the mechanism of the pineal gland?
pineal gland contains photoreceptors that make its melatonin release cycle LD entrainable, norepinephrine can also entrain the release of melatonin
what is the circadian clock mechanism of anolis carolinesis?
pineal releases melatonin rhythmically, pineal gland is both output of system and part of system
what is the mammalian circadian clock mechanism?
SCN (specifically dorsomedial) most important oscillator, other oscillators include retina, raphe nuclei, food, meth, time memory
how do we know SCN is the clock?
location, ablation, transplantation, explantation, tau hamster transplant (Lucy Always Tries Every Taco)
what is ablation?
experimentation on individuals with destroyed/damaged SCNs
what is explantation?
rhythms can be measured from SCN in vitro
why is the mammalian pineal gland different?
it is not photosensitive
what is melanopsin?
unique mammalian photopigment
how does photic information reach the SCN in mammals?
photoreceptors in ganglion cells of retina, large receptive fields project to SCN via retinohypothalamic tract
T or F: all vertebrates have pacemakers in pineal gland
FALSE AF
T or F: electrical stimulation of IGL creates nonphotic phase shifts in hamsters
TRUE
T or F: melanopsin is a neurotransmitter in the mammalian RHT
FALSE
T or F: NPY is a neurotransmitter in the mammalian RHT
FALSE
T or F: melatonin is required for behavioural rhythmicity in hamsters
FALSE
T or F: hamsters without a dorsomedial SCN can still entrain to LD cycles
FALSE
what happens after complete ablation of the SCN in rats?
arrhythmicity
what happens after NPY is injected during subjective day?
mimicry of effects of novelty induced wheel running
T or F: humans exhibit more than one circadian oscillation
TRUE
what can block effects of novelty induced wheel running?
physical restraints (WOW DUH)
what did Kalmur demonstrate?
clock is metabolically based and endogenous
what will a perfectly temperature compensated clock have?
Q10 of 1
what phenomenon is not included in Aschoff’s rules?
when light intensity increases diurnal animals will decrease activity
T or F: for an animal with tau = 23 hrs each circadian hour is longer than a real hour
FALSE
T or F: Bunning’s temp experiments demonstrated that clocks are temp dependent
FALSE
T or F: an animal with tau = T has a clock that is not responsive to light
FALSE
T or F: nocturnal and diurnal animals are active in their subjective day
FALSE
T or F: an organism with tau = 25 hrs needs a 1 hr advance each day to entrain to a 24 hr T
TRUE
what is the significance of the phase angle?
determines animal’s activity relative to a stable zeitgeber
why does tau not equal 24hrs?
organism will not be able to adapt well to any environmental stressors
if the limit of entrainment is +/- 3hrs, how would an organism with tau - 27hrs entrain to a 22hr day?
using nonphotic that compound with photic stimuli the entrainment can go past the limit
what is the common element of nonrhotic, phase shifting stimuli?
behavioural activation or arousal
what neurotransmitter does the PPT release into the IGL?
acetylcholine
what are the effects caused by pineal gland lesions in sparrows?
arrhythmicity in DD
in what species what the first clock mutant identified?
drosophila
T or F: lizard clock is located in pineal gland
FALSE
T or F: mice without eyes are rhythmic in LD cycles
TRUE
what is the effect on human free running period after lesioning the raphe nuclei?
free running period continues
where are photoreceptors found in avian tissue?
pineal gland and deep brain tissue
T or F: person flown from Toronto > Vancouver needs 3hr delay to entrain
TRUE
T or F: in some mammals the pineal gland can function as a clock
FALSE
T or F: tau mutant clocks run slower
FALSE (faster)
what happened in Ralph’s tau mutant experiment? (so obnoxious to reference himself ew)
giving a hamster an SCN lesion caused arrhythmicity, when fetal tau mutant SCN transplanted into lesioned hamster, hamster displayed tau mutant behaviour of donor
why are clocks not equal in period to the cycle that entrains them?
when days are short the phase angle of entrainment can drift because long as light continues to fall during subjective day, there will be no effect on phase shift or entrainment; biological variability causes a rhythm close to ZT to have a slightly different period
what are 4 major biological clocks?
circadian, circannual, circatidal, circalunar
