seasonal regulation Flashcards
effect of constant photoperiod on seasonal rhythms
no effect, seasonal rhythms persist in constant photoperiod
why do species near the equator have a circannual rhythm instead of responding to photoperiod
at the equator, there isn’t much change in photoperiod
when are circadian rhythms not entrainable
- day < 20h
- day > 28h
what dictates seasonal physiology
photoperiod
when are testes of hamsters vs sheep bigger in size and why
hamsters during summer and sheep during winter because depends on gestation time/reproductive period
prolactin secretion in hamsters vs sheep
same pattern of secretion -> winter = low secretion; summer = high secretion
what does pineal melatonin rhythm encode
day length information
where is melatonin receptor 1 expressed
pars tuberalis (underneath median eminence)
what converts t4 to t3
deiodinases2 (DIO2)
expression of kiss1 in sheep vs hamsters
sheep = high in winter; hamster = high in summer (inverse seasonal expression)
tsh expression in sheep: winter vs summer
summer = expression; winter = no expression
tshb expression under long and short days in pars tuberalis
increase in expression during the day (light period)
relationship bw eya3 and TSH
eya3 drives tsh
eya3 is transcriptionally controlled through (2)
- e boxes
- d elements
what controls eya3 and how
circadian clock; bmal1/clock binds e boxes on eya3 gene and drives eya3 expression
after how long does eya3 stop being suppressed and effects (2)
stops being suppressed after 12h -> if happens to be during dark, eya3 suppressed again; if happens to be during light, activate eya3 and reproductive switch
effect of melatonin on eya3
melatonin treatment suppresses eya3
what possibly regulates eya3 promoter
camp
where is eya3 expressed
pars tuberalis
where are season-specific differences in reproductive drive encoded
downstream of DIO2
pathway of regulation of seasonal rhythms
clock -> eya3 -> tsh -> t3 & t4 -> kiss1 -> gnrh neurons
when do seasonal changes in tsh and dio2 occur
- photoperiodic changes
- absence of photoperiodic changes
while measuring cage activity, what fluctuated in hamsters under constant light (no photoperiod changes)
body weight and locomotor period (reflection of seasonal timer)
rhythmicity of animals living in communities
absence of 24h rhythmicity -> run on endogenous rhythm
