Chapter 10: Biological Rhythms and Sleep Flashcards
Differentiate between circadian rhythms, ultradian rhythms, and infradian rhythms and give an example of each.
Circadian rhythm - 24 hour period.
Ultradian rhythm - more than once a day (e.g., bouts of activity, feeding, and hormone release)
Infradian rhythm - less than once a day (e.g. body weight and reproductive cycles repeat
Describe phase shift, entrainment, and a zetigeber.
Phase shift: the shift in activity in response to a synchronizing stimulus, such as light or food (jet lag)
Entrainment is the process of shifting the rhythm (biological clock entrains to our environment)
Time-giver: the cue that an animal uses to synchronize with the environment.
What is our endogenous clock and what do lesions of this area produce?
The suprachiasmatic nucleus (located above the topic chiasm in the hypothalamus)
Studies in SCN-lesioned animals showed disrupted circadian rhythms.
Isolated SCN cells maintain electrical activity synchronized to the previous light cycle.
What pathway does light travel along to from the eye to the SCN? Describe the retinal ganglion cells involved in this process.
The retinohypothalamic pathway. Some retinal ganglion cells project to the SCN. Most contain melanopsin, a special photopigment, that makes them sensitive to light.
Describe the process of how Clock and Cycle genes work.
SCN cells make two proteins: Clock and Cycle. These fuse together to make a dimer.
The Clock/Cycle dimer promotes transcription of two genes: period (per) and cryptochrome (cry).
The per and cry proteins bind to each other and this complex enters the nucleus and inhibits the transcription of per and cry.
No new proteins are made until the first set degrades. This cycles repeats about every 24 hours.
In the absence of cues, humans have a free-running period of approximately 25 hours (True or False).
True
Name and describe the two distinct classes of sleep.
- Slow-wave sleep (SWS) can be divided into three stages and is characterized by slow-wave EEG activity.
- Rapid-eye-movement sleep (REM) is characterized by small amplitude, fast EEG waves, no postural tension, and rapid eye movements
Describe the pattern of activity in an awake person vs in an asleep person.
Awake person:
- dominated by waves of fast frequency and low 12 amplitude (15-20 Hz)
- known as beta activity or desynchronized EEG
Asleep/relaxed person:
- alpha rhythm occurs in relaxation, a regular oscillation of 8-12 Hz
Describe the 4 stages of slow-wave sleep:
- Stage 1 sleep
- shows events of irregular frequency and smaller amplitude, as well as vertex spikes, or sharp waves
- heart rate slows, muscle tension reduces, eyes move about
- lasts several minutes - Stage 2 sleep
- defined by waves of 12-14 Hz that occur in bursts, called sleep spindles
- K-complexes appear - sharp negative EEG potentials - Early-stage 3 sleep
- continued sleep spindles as in stage 2
- defined by the appearance of large amplitude, very slow waves called delta waves.
- delta waves occur about once per second
- delta waves are the dominant pattern in late stage 3. - REM sleep
- active EEG with small amplitude, high-frequency waves like an awake person
- muscles are relaxed - called paradoxical sleep
- strong visual component (REM, occipital lobe)
Describe a typical night of young adult sleep
- sleep time ranges from 7-8 hours
- 45-50% is stage 2 sleep, 20% is REM sleep,
- Cycles last 90-110 minutes, but cycles early in the night have more stage 3 SWS, and later cycles have more REM sleep.
Differentiate between night terrors and nightmares.
Nightmares are frightening dreams that awaken the sleeper from REM sleep
Night terrors are sudden arousals from stage 3 SWS, marked by fear and autonomic activity.
Discuss the effects of sleep deprivation and how sleep recovery occurs.
Effects of sleep deprivation:
- increased irritability
- difficulty in concentrating
- episodes of disorientation
Sleep reocvery is the process of sleeping more than usual after a period of deprivation
Night 1 - stage 3 sleep shows the greatest increase relative to normal, at the expense of stage 2 sleep
Nights 1 and 2 - REM sleep increases; it is also more intense than normal, with more rapid eye movements.
Discuss sustained sleep deprivation in rats.
Sustained sleep deprivation in rats causes an increase in their metabolic rate, weight loss, and death within about 19 days.
Total sleep deprivation compromises the immune system and leads to death.
What is fatal familial insomnia?
It is inherited - in midlife people stop sleeping and die 7-24 months after onset of the insomnia.
What are the four functions of sleep?
- Energy conservation
- muscular tension, heart rate, blood pressure, temperature, and rate of respiration are reduced. - Niche adaptation
- sleep helps animals avoid predators. Animals sleep during the part of the day when are they are most vulnerable. - Body ad brain restoration.
- Sleep restores the body by restoring materials used during waking hours, such as proteins.
- most growth hormone is only released during SWS.
- proper sleep is essential for immune function. - Memory consolidation
- sleep during the interval between learning and recall improves retention.
- learning of perceptual skills is improved by a period of REM sleep
- consolidation of declarative memory tasks and complicated motor skills seems to benefit from SWS.
