Rhythms of Waking and Sleeping

Which of the following people would be most alert when watching a late-night movie?

20 year old

What is the principal zeitgeber for land animals?

Light

After isolating a neuron from the rest of the brain, you find that it has a moderately stable circadian rhythm. The most likely home of this neuron is in the:

SCN.

How is the circadian rhythm of adult hamsters affected after transplanting SCN tissue from hamster fetuses with abnormal (20 hour) circadian rhythms?

The adult hamsters adopted the rhythm of the transplanted tissue.

What happens if people are put in an environment that is constantly light?

They complain that they cannot sleep.

In one family that has a mutation in the gene responsible for their PER protein, behavior changed in what way?

They liked to go to bed early and wake up early.

An astronaut orbiting earth experiences 45-minute periods of daylight alternating with 45-minutes of darkness. What is likely to happen?

They sleep poorly during rest periods.

Suppose you work on a submarine with only artificial light. You are required to follow a schedule of working for 12 hours and then sleeping for 6. What rhythm, if any, will your alertness and body temperature show?

They will follow the usual rhythm of 24 hours.

When traveling across time zones, adjustments are easier when traveling which direction?

Travel to the west is easier.

The PER and TIM proteins accumulate during the day until they cause sleepiness. What prevents them from continuing to accumulate at night?

When the proteins reach a high level, they turn off the genes that produce them.

When do the secretions of melatonin begin?

a couple of hours before a person naturally falls asleep

If a migratory bird is kept in a laboratory room with constant temperature and 12 hours of light each day, when does it show migratory restlessness?

at approximately the correct time of year for migration

Circadian cycles are to ____ as circannual cycles are to ____.

daily; yearly

Alternation of TIM protein levels by a pulse of light during the night will:

decrease sleepiness.

A "zeitgeber" is a(n):

environmental cue that resets a biological clock.

Researchers have demonstrated that the expression of the SCN genes can be changed through:

exposure of the eyes to light.

Mammals have circadian rhythms:

for a variety of activities, including sleep.

The role of the suprachiasmatic nucleus (SCN) in the regulation of biological rhythms is to:

generate the circadian rhythm.

Taking melatonin pills in the late evening:

has no noticeable effects.

A disruption of circadian rhythms due to crossing time zones is known as:

jetlag.

Which of the following would most likely help someone adjust to jet lag?

keeping the room light when you need to stay awake

Animals produce endogenous circadian rhythms that:

last about a day.

When the PER and TIM levels increase, they feed back to inhibit the genes that produce the ____ molecules.

messenger RNA

The SCN is located just above the:

optic chiasm.

Suppose you fell into a cave and lost your watch. Without any time cues, your circadian rhythm would:

remain relatively stable.

The circadian rhythm is reset by input from special ganglion cells in the retina. These ganglion cells are unusual in that they:

respond directly to light, but respond very slowly.

The retinohypothalamic pathway receives input from the:

retinal ganglion cells that respond directly to light.

Alteration of the per gene in humans is associated with:

shortened circadian rhythms.

After damage to the suprachiasmatic nucleus, the body:

still has rhythms, but they are less consistent.

The surest way to disrupt the biological clock is to damage the:

suprachiasmatic nucleus.

When the PER and TIM levels are low, they result in:

wakefulness.

A stimulus that resets the circadian rhythm is referred to by the German term:

zeitgeber.