Chapter 10 Flashcards
What are biological rhythms?
Regular fluctuations in any living process
What are circadian rhythms?
Physical, mental, and behavioral changes that follows a 24 hour cycle
What is within Circadian rhythms?
- Hormones: Melatonin & Corticosterone
* Sleep/Wake
* Body Temperature
* Aggression/Anger
What is Ultradian rhythms?
Biological cycles that takes place within 24 hrs (<24). Repeats more than once a day
What is apart of Ultradian rhythms?
- Feeding & related hormones release
* Bouts of activity
What is Infradian rhythms?
Repeats longer than a day
What is included in infradian rhythms?
- Emotion/mood
* Reproductive cycle
* (menstrual/estrus cycles)
Humans are diurnal
Active during the day
What is free-running?
Animals deprived of external cues about time of day, maintains their own personal cycles; tend to be longer than normal circadian rhythm
What is a free-running period?
The time between two similar points of successive cycles; ex, sunset to sunset
What is phase shift?
A shift in the activity of a biological rhythm, typically provided by a synchronizing environmental stimulus; ex. Light
What is entrainment?
The process of synchronizing a biological rhythm to an environmental stimulus; ex. A hamster synchronizing it’s wheel to the start of the dark period when subjected to periods of light and dark
What is Zeitgeber?
The stimulus that entrains circadian rhythms
What is the suprachiasmatic nucleus (SCN)?
Lesions of a tiny subregion of the hypothalamus and the location of the circadian clock
What do lesions of the suprachiasmatic nucleus eliminate?
Circadian rhythms of drinking, locomotion, and hormone secretion
What happens to isolated SCN cells?
They continue to show a circadian rhythm for days or weeks
SCN is necessary and sufficient to produce circadian rhythm-controlled behaviors
What does melatonin inform?
It informs the brain about day length (the pineal gland forms the hormone melatonin)
Circadian rhythms entrain to light-dark cycles using different pathways; some are outside of the eye (ex.birds)
In mammals, some retinal ganglion cells form the retinohypothalamic pathway
What is the retinohypothalamic pathway?
Pathway, which Carrie’s light information from the eyes to the SCN
What special photopigment makes mammals sensitive to light?
Melanopsin; that is why mammals don’t rely on traditional photoreceptors to learn about light
What increased our understanding of the circadian clock in mammals?
Molecular studies in Drosophila (flies) and mice’s using mutations of the period gene (per) and cryptochrome (cry)
What two proteins do SNC cells make in mammals?
Clock and Cycle
What do Clock and Cycle proteins form by binding together?
Dimer
What is a dimer?
a pair of proteins attached to each other
What two genes does the Clock and Cycle dime promote transcription of?
Period (per) and Cryptochrome (cry); clock and cycle binds to the cells DNA to do this; takes 24 hours to complete
What happens when Per and Cry protein bind to each other?
It inhibits the activity of the Clock/Cycle dimer thus slowing the transaction of per and cry genes
What happens when Per and Cry proteins break down?
They release the Clock/Cycle from inhibition, allowing the cycle to start over again
What are larks?
People who feel energetic in the morning; likely to carry a different version of the clock gene than night owls
What do transplant studies provide supporting evidence for?
That the SCN produces the circadian rhythm
What did hamsters with SCN lesions in constant conditions show?
No circadian rhythm of running wheel activity
What happened when hamsters received an SCN tissue transplant from hamsters with a short circadian rhythm?
Circadian rhythms were restored but it matched the shorter period of the donor
