L11 Biological Rhythms Flashcards
biological rhythm
recurrent physiological or behavioral event that happens repeatedly in a set pattern
4 behavioral biological rhythm
1) general activity (diurnal, nocturnal, crepuscular)
2) reproduction
3) migration
4) hibernation
4 physiological biological rhythms
1) heart rate
2) body temperature
3) HPG axis
4) insulin / glucagon release
presence of rhythms depends on…
time scale
biological rhythms typically have a set…
period, frequency, and amplitude
period
length of time from one point in the cycle to the next
frequency
number of cycles per unit time
amplitude
change in value above or below the average
exogenous rhythms triggered by…
stimuli outside of an animal
endogenous rhythms regulated by…
internal stimuli; requires an internal “biological clock”
biological clock
innate mechanism that controls biological rhythms of organisms
3 characteristics of biological clock
1) free-running period
2) entrainment
3) zeitgeber
free-running period
length of time from start of one cycle to the next in constant conditions
entrainment
process of synchronization of endogenous rhythms to an environmental cue
zeitgeber
“time giver”; rhythmic period cue that entrains biological clocks
what brain region is responsible for the biological clock?
suprachiasmatic nucleus (SCN)
to find the location of the biological clock, researchers did what?
lesioned areas of the hypothalamus (PVN, VMH, POA, SCN)
SCN neurons in vitro show what?
rhythmic firing rates that can last for years
WT SCN has free running period of…
22-24.5 hrs
tau mutants have free running period of…
20 hrs
transplanting SCNs between WT and tau mutants results in…
recipients demonstrating donor’s free-running period
SCN is entrained by light activating the…
retinohypothalamic tract (RHT)
neural activity from SCN projects to…
pineal gland
pineal gland secretes melatonin in proportion to…
length of dark phase (night)
