Biological Rythms Flashcards
Most animals can measure time
Bio clocks found in every eukaryotic organism tested
Rhythmical nature makes sense with evolution
Anticipation of environmental change
Why bio rhythms?
Anticipate environmental change: fruit flies
Synchronize behavior with other events: bees
Measure time: honeybee
Endocrine function
Shows rhythmic variation over time
Circadian rhythm
About a day, 24 hours
Body temp
Sleep/wake
Ultradian
Shorter than day
Sleep cycle
Hunger
Attention span
Infradian
Longer than a day
Menstrual cycle
Hibernation
Migration
Circannual
Yearly Hibernation Migration Some reproduction Garden warbler
Biological rhythms can be
Internal: controlled by bio clock
External: external stimuli sync internal cycles
Zeitgeber
Time giver, exogenous stimuli
Entrainment
Sync with periodic cue in environment
Jean Jacques Dortous De Mairan
Identified internal bio clock
Found in plants
Organization of circadian rhythms
Single cells, no need for complex nervous system
No single clock, fruit flies have multiple
Master clock
Entrained by light dark cycle
Controls all clocks
Photoreceptors control time
Retina hypothalamic tract (RHT)
Where is master clock
SCN suprachiasmatic nucleus Independent Spontaneous Self sustaining Found directly above optic chiasm
3 main components
Photoreceptors
SCN
Clock controlled genes
Genetic basis of circadian cycle
Self regulated feedback loop Clock and BMAL1 bind together and enter nucleus Turn on activity of period and crypto chrome genes Bind with tau to form complex Suppresses clock and BMAL1 Results in less per and cry Tau complex declines Turns on again
Central oscillator
Controls bio rhythms
Reset by external light signal
Peripheral oscillator
Slave
Regulate local rhythms
Reset by feeding
Signals from SCN
Preoptic nucleus to hypothalamus: rhythm of ovulation
Paraventricular nucleus in hypo: neuron endocrine plus autonomic
Leads to pineal which produced melatonin
Can be hormonal: melatonin and glucocorticoids
Hormones entrain peripheral oscillators
Melatonin: body temp Rhythm
Glucocorticoids: steroid hormones that control physiology
Melatonin
Pineal gland Connected to eyes Converted from serotonin Sleep and learning Antioxidant Protects fetus Mediated hormones Helps immune system Neirodegenerative diseases Helps set sleep rhythms Could help with depression
Leptin/ghrelin
Decreased appetite, increased appetite
Chronobiology
Scientific study of biological clocks and associated rhythms
A biological rhythm is any cyclic change in level of bodily chemical or function
