Question 1

Companies that employ shift workers have improved productivity and job satisfaction by

Accepted Answer

Scheduling only phase delays (such as moving a work shift later, rather than earlier) tends to be more in line with the natural circadian rhythms of most people, making it easier for shift workers to adjust, potentially improving productivity and job satisfaction.

Question 2

Bilateral lesions of the __________ selectively disrupt circadian cycles.

Accepted Answer

The suprachiasmatic nuclei play a crucial role in regulating circadian rhythms, so bilateral lesions of this area would disrupt this process. Lesions of the other structures listed may impact sleep/wake regulation or other aspects of physiology, but not necessarily specifically disrupt circadian rhythms.

Question 3

Cells of the suprachiasmatic nuclei display circadian cycles of

Accepted Answer

The suprachiasmatic nuclei are the central pacemaker for the circadian rhythm in mammals. These cells display rhythms of gene expression that drive the circadian cycle.

Question 4

The entrainment of circadian rhythms by visual zeitgebers is mediated by

Accepted Answer

The entrainment of circadian rhythms by visual zeitgebers involves all of the listed elements: part of the optic nerve, the retinohypothalamic tract, and a rare type of retinal ganglion cell. These components work together to transmit light information from the environment to the brain's internal clock mechanisms.

Question 5

The first circadian gene to be discovered in mammals was

Accepted Answer

The answer of The first circadian gene to be discovered...

Question 6

Studies of encephalitis lethargica suggested that the

Accepted Answer

Studies of encephalitis lethargica suggested that damage to the posterior hypothalamus leads to excessive sleepiness while damage to the anterior hypothalamus leads to insomnia. Therefore, the posterior hypothalamus promotes wakefulness while the anterior hypothalamus promotes sleep. The basal forebrain is involved in the regulation of many functions including sleep, but it mainly promotes non-REM sleep and inhibits wakefulness.

Question 7

Under normal living conditions,most people sleep during

Accepted Answer

The falling phase of the circadian body-temperature cycle is typically associated with sleep onset.

Question 8

The fact that most people sleep almost exactly the same amount each day under free-running conditions,despite large day-to-day variations in physical and mental activity,provides strong support for the dominance of

Accepted Answer

The fact that people sleep almost the same amount each day despite variations in activity suggests that sleep is primarily regulated by circadian factors (internal biological clock) rather than recuperative factors (need for restoration after activity) or external factors such as light cycles or temperature.

Question 9

The first mammalian circadian gene to have its structure characterized was

Accepted Answer

The first mammalian circadian gene to have its structure characterized was the Clock gene, which plays a crucial role in the regulation of circadian rhythms in mammals.

Question 10

Bilateral transection of the optic nerve,as indicated by the arrow,

Accepted Answer

Bilateral transection of the optic nerve eliminates the ability of light to entrain circadian rhythms, because the optic nerve carries light information from the retina to the suprachiasmatic nucleus (SCN) in the hypothalamus, which is responsible for regulating circadian rhythms. However, it does not affect the corpus callosum, fornix, or sleep directly.

Question 11

The main evidence that circadian sleep-wake and body-temperature cycles are not causally related is that they

Accepted Answer

DCircadian sleep-wake and body-temperature cycles can sometimes become internally desynchronized under free-running conditions, such as in the absence of external time cues. This indicates that they are controlled by separate mechanisms since they can operate independently. Additionally, these cycles usually have different free-running periods when not influenced by external factors, further supporting their independence.

Question 12

In the neurotransplantation experiment by Ralph and colleagues,the suprachiasmatic nuclei (SCN)were transplanted from the fetuses of mutant hamsters that had abnormally brief free-running sleep-wake cycles into normal adult hamsters whose sleep-wake cycles had been abolished by SCN lesions.The transplants initiated __________ sleep-wake cycles in the recipients.

Accepted Answer

The transplants initiated 20-hour free-running sleep-wake cycles in the recipients, reflecting the abnormal cycle length of the donor mutant hamsters.

Question 13

Eastern flights

Accepted Answer

Traveling eastward typically causes phase advances in our circadian rhythms because we are moving into time zones where the local time is ahead of our body's internal clock, requiring us to adjust by going to sleep and waking up earlier than we are accustomed to.

Question 14

There is more than one circadian clock: This conclusion is supported by the finding that bilateral lesions of the

Accepted Answer

According to the statement, bilateral lesions of the suprachiasmatic nuclei do NOT abolish circadian rhythms, indicating that there may be other circadian clocks in the body. Therefore, option B is the best choice.

Question 15

Studies of encephalitis lethargica suggested that the __________ promotes wakefulness

Accepted Answer

The posterior hypothalamus is involved in promoting wakefulness, as suggested by studies of encephalitis lethargica.

Question 16

Clock is a circadian gene; it was discovered in

Accepted Answer

Clock was discovered in mice in 1994 by Joseph S. Takahashi and his team.

Question 17

The diurnal light-dark cycle entrains the sleep-wake cycle via the

Accepted Answer

The retinohypothalamic tracts, which connect the retina to the suprachiasmatic nucleus (SCN) in the hypothalamus, are responsible for entraining the sleep-wake cycle to the diurnal light-dark cycle. The SCN serves as the body's "master clock" and regulates circadian rhythms.

Question 18

There is good evidence that the internal circadian clock is located in the

Accepted Answer

The suprachiasmatic nuclei (SCN) have been identified as the location of the internal circadian clock in mammals. This area is located in the hypothalamus, just above the optic chiasm, and receives direct input from the retina regarding the presence or absence of light.

Question 19

Exposure to intense light early in the morning following an east-bound flight

Accepted Answer

Exposure to intense light early in the morning following an east-bound flight helps to reset the biological clock and accelerate adaptation to the advanced time zone. This is because exposure to light (especially bright light) in the morning signals to the body that it is time to wake up and start the day, helping to shift the body's circadian rhythms to the new time zone.

Question 20

Under free-running conditions,longer periods of wakefulness are usually followed by

Accepted Answer

The answer of Under free-running conditions,longer periods of wakefulness are...

Quiz 14: Sleep, Dreaming, and Circadian Rhythms