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Chapter 11

PSYB64H3 Chapter Notes - Chapter 11: Cataplexy, Raphe Nuclei, Sleepwalking

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Janelle Leboutillier

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PSYB64- Chapter 11: Sleep and Waking (LECTURE AND TEXTBOOK)
-circadian rhythms is a repeating cycle of about 24 hours for sleep and
-Zeitgebers- is an external cue(or a stimulus) for setting biological rhythms. Light is
the most important zeitgebers for human beings.
-Free running circadian rhythm- A rhythm that is not synchronized with external
cues. Without zeitgebers, FRCR, lasts for approximately 24.2 24.9 hours.
-entrainment is the resetting of the human biological clock to 24 hour cycle of the
earth’s rotation due to the exposure of sunlight
Variation in sleeping patterns
-Individuals sleeping patterns are different because of the different versions genes
for our internal clocks.
-People who are productive in the morning are referred to as larks
-People who are more productive in the night are referred to as night owls.
-Almost everyone is known to be a night owl when they are adolescent
This is because the drop in melatonin(neurochemical involved in sleeping
regulation pattern) at the onset of puberty.
Shift work, Jet Lag and Daylight savings time
-people who do night shifts get 1.5 hours of less sleep that normal shift workers.
This causes them to make mistakes while doing work. This also risky to their health.
It also causes shift maladaptation syndrome
-Jet lag is the unsettling experience you get when there is a conflict between
internal clocks and external zeitgebers.
After crossing time-zones people experience fatigue, irritability and
It is easier to adjust a phase delay than a phase advance
Daylight savings time in spring requires a phase advance (an hour less of
sleep) and can produce symptoms similar to jetlag
The change in fall is equivalent to phase delay and causes little disruptions
for most people because you get an extra hour of sleep.
Jet lag is also worse when travelling east because you go backwards in
time.(if you wake up at 6 am, it feels like you wake up at 3 am)
Jet lag isn’t as bad travelling west because you go forward in time (if you
wake up at 6am, it feels like you wake up at 9 am)
Internal Clocks
-The body’s master internal clock is the Suprachiasmatic Nucleus (SCN), which is
located in the hypothalamus above the optic chiasm, is responsible for maintaining
circadian rhythms
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Retinohypothalmic pathway is a pathway leading from the retina of the eye
to the hypothalamus, which provides light information necessary for the
maintenance of the circadian rhythms.
Melanopsin is a photopigment used by the non-image-forming (NIF) retinal
Diurnal is someone who is active during the day and nocturnal is someone
who is active during the night.
SCN is only active during the day regardless if you are diurnal or nocturnal
If SCN is transplanted from a hamster with short free running cycle to a
normal free running cycle, the behavior of the hamster will act like the
hamster with short free running cycle and vice versa
Rhythms of the SCN are heavily influenced by the presence of light
However peripheral clocks are more easily influenced by the daily feeding
If you feed nocturnal mice during the day, it will change their circadian
rhythms by influencing these peripheral clocks.
Cellular Basis of the Circadian Rhythms
-How can SCN tell time?
Answer lies in the oscillation of protein production and degeneration within
the cell.
There are three protein products that are involved with the circadian rhythms
Per(period) tim(timeless), and clock (circadian locomotor output cycles
These were found by doing research with fruit flies
Per and time together inhibit the clock protein
And Clock protein promotes the production of more per and time proteins
See cycle in figure 11.6
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Biochemistry and Circadian Rhythms
-Two main hormones are used in the circadian rhythms: Melatonin and Cortisol
- Melatonin, a hormone secreted by the pineal gland which participates in the
circadian rhythms
The SCN regulates and responds to this hormone
Lesions of the SCN abolishes the release of melatonin
Melatonin levels are really low during the day and begin to rise hours before
sleep and peak at 4 am. (which is why people have difficult time staying
Bright lights suppress melatonin
Melatonin supplements help jet-lags, shift maladaptation syndrome and
other sleeping disorders
Individuals with Autism spectrum disorder have low levels of melatonin
-Cortisol is a hormone released by the adrenal glands that promotes arousal.
Levels of Cortison are usually high in the morning and low in the night
High level of cortisol are related with high blood pressure, high heart rate
and mobilization of body’s energy stores
Cortisol is also released during the time of stress
Cortisol also contributes to times of jet lags
Seasonal Affective Disorder
-During winter months, the reduction in daylight may interfere with the circadian
rhythms causing depression known as seasonal affective disorder
- Seretonin levels drop in the fall and winter and people who have the SAD have a
greater increase in serotonin levels than usual people, which causes depression
-SAD might also be influenced by disruptions in the melatonin releases due to the
uneven patterns of daylight
-We can place wakefulness and sleep along a continuum of brain activity using EEG.
Desynchronous is a brain activity that arises from independent activity of
neurons and is correlated with alertness. It also means having different
periods and phases; in EEG it represents high levels of brain activity. (many
different swimmer swimming at a swimming pool; a lot of diversity)
Synchronous is a brain activity that occurs when neurons are firing in more
of a union and characterizes deep stages of sleep. It has identical periods and
phases; in EEG it represents low levels of brain activity (swimming team
swimming at a swimming pool; not much diversity)
-During wakefulness, EEG recordings alternate between beta waves and alpha
waves of the brain activity
Beta waves= highly desynchronized, irregular and low amptitude.
Associated with high levels of alertness during wakefulness
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