Module 9.1 Flashcards
What are endogenous cirannual rhythms?
self-generated rhythm that lasts about a year
What are endogenous circadian rhythms?
self-generated rhythms that last about a day
What sorts of attempted interference with the biological clock were not effective?
induced hibernation
What are some bodily and behavioral changes that occur in circadian rhythms?
Waking and sleeping, eating, urination, secretion of hormones, sensitivity to drugs, and temperature change
How can circadian rhythms be demonstrated experimentally?
Scientists demonstrated the circadian rhythm by keeping flying squirrels in the dark for 25 days. Even in this environment, the animals generated a regular rhythm of activity and sleep.
How easily can humans adapt to a new cycle length? What are the limits of adaptation?
It’s difficult for humans to adapt to a new cycle length. We can’t make our cycles very much longer than 24 hours.
What structure is the source of the circadian rhythm?
suprachiasmatic nucleus
What is the SCN’s relationship tot he visual system?
A small branch of the optic nerve extends directly from the retina to the SCN and taxons of hat path alter the SCN’s settings
What evidence indicates that the suprachiasmatic nucleus generates its own rhythms?
If SCN neurons are disconnected from the rest of the brain or removed from the body and maintained in tissue culture, they continue to produce a circadian rhythm.
What happened when SCN tissue from hamsters with a mutant gene for a 20-hour rhythm were transplanted into normal hamsters?
The recipent produced a 20-hour rhythm
What two genes govern circadian rhythms?
period and timeless
How do period and timeless work?
these proteins start in small amounts in the morning and increase during the day
What is melatonin?
a hormone that influences circadian and cirannual rhythms
From which gland is melatonin secreted?
pineal gland
When does increased secretion of melatonin occur?
at night
What is a Zeitgeber?
the stimulus that resets the circadian rhythm
What is the most effective Zeitgener for land animals?
light
Is it easier to cross time zones going east or west? Why?
Going west; because you are already partly adjusted to the schedule because you go to sleep later and wake up later the next morning.
What is the best way to reset the biological clock when working the night shift?
Sleep in a very dark room during the day and work under very bright lights
By what path does the retina influence the SCN?
retinohypothalamic path
What is unusual about the ganglion cells whose axons make up the retinohypothalamic path? How rapidly do they respond to light?
they have their own photopigment; they respond to light slowly
How can circadian rhythms be demonstrated experimentally?
by using light
