Chapter 8: Wakefulness and Sleep Flashcards
What evidence indicates that humans have an internal biological clock?
People who have lived in an environment with a light–dark schedule much different from 24 hours fail to follow that schedule and instead become wakeful and sleepy on about a 24-hour basis.
Why do people at the eastern edge of a time zone awaken earlier than those at the western edge on their weekends and holidays?
The sun rises earlier at the eastern edge than at the western edge. Evidently, the sun controls waking–sleeping schedules even when people follow the same clock time for their work schedule.
What evidence strongly indicates that the SCN produces the circadian rhythm itself?
SCN cells produce a circadian rhythm of activity even if they are kept in cell culture isolated from the rest of the body. Also, when hamsters received transplanted SCN neurons, their circadian rhythm followed the pattern of the donor animals.
How does light reset the biological clock?
A branch of the optic nerve, the retinohypothalamic path, conveys information about light to the SCN. The axons comprising that path originate from special ganglion cells that respond to light by themselves, even if they do not receive input from rods or cones
People who are blind because of cortical damage can still synchronize their circadian rhythm to the local pattern of day and night. Why?
If the retina is intact, melanopsin-containing ganglion cells can still send messages to the SCN, resetting its rhythm.
How do the proteins TIM and PER relate to sleepiness in Drosophila?
The proteins TIM and PER remain low during most of the day and begin to increase toward evening. They reach high levels at night, promoting sleep. They also feed back to inhibit the genes that produce them, so that their level declines toward morning.
According to a study by Kelly et al. (1999), naval personnel on submarines were asked to function on 18-hour “shifts”: 6 hours of work, 6 hours of recreation, and 6 hours of sleep. What happened to their circadian rhythms?
a. They had a hard time deviating from the 24-hour schedule.
b. Nothing, because they were quickly able to adapt to the 18-hour schedule.
c. They adapted to the 18-hour schedule, but it took a few months.
d. They eventually adopted a 36-hour circadian rhythm.
They had a hard time deviating from the 24-hour schedule
Correct. Even though the naval personnel were kept on the 18-hour shifts, they had a hard time deviating from the 24-hour schedule. Even though they tried to sleep on this schedule, their bodies generate rhythms of alertness and body chemistry that averaged about 24.3 hours.
The most potent zeitgeber for land mammals is the _____.
a. seasons
b. sunlight
c. tides
d. temperature
Sunlight
Correct. When we are free to set our own schedules, we tend to deviate slightly from the 24-hour period. However, we typically have our rhythms reset by the most potent zeitgeber, light.
Carlos is being changed to an overnight shift at work. What would be the best conditions for him so that he adjusts?
a. He needs to buy dark curtains for the daytime and work under bright lights.
b. He needs to work under dim artificial light.
c. He needs to sleep with dim light on to reset his rhythm.
d. He needs to work under bright lights and sleep with dim light on
He needs to buy dark curtains for the daytime and work under bright lights.
Correct. When adjusting to a night shift, people like Carlos will adjust best if they sleep in a very dark room (with dark curtains for example) and work in very bright lights as opposed to the normal artificial lights that are rather dim.
What do large, slow waves on an EEG indicate?
Large, slow waves indicate a low level of activity, with much synchrony of response among neurons.
How can an investigator determine whether a sleeper is in REM sleep?
Examine EEG pattern and eye movements
During which part of a night’s sleep is REM most common?
REM becomes most common toward the end of the night’s sleep.
Why do most antihistamines make people drowsy?
A pathway from the hypothalamus uses histamine as its neurotransmitter to increase arousal. Antihistamines that cross the blood–brain barrier block those synapses.
What would happen to the sleep–wake schedule of someone who lacked orexin?
Someone without orexin would alternate between brief periods of waking and sleeping.
What would happen to sleeping and waking if you took a drug that blocked GABA?
You would remain awake, or at least somewhat conscious. (Tranquilizers put people to sleep by facilitating GABA.)
