PS101 Chapter Notes - Chapter 5: Chronobiology, Mescaline, Methadone

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30 Jan 2013
Body Rhythms and Mental States
Consciousness: awareness of oneself and the environment
Biological Rhythms: The Tides of Experience
Biological Rhythm: a periodic, more or less regular fluctuation in a biological system; may or may
not have psychological implications
Biological clock in brains governs waxing and waning of hormone levels, urine volume, blood
pressure, and even the responsiveness of brain cells to stimulation
Entrainment: the synchronization of biological rhythms with external cues, such as fluctuations
in daylight
Endogenous: generated from within rather than by external cues
Circadian Rhythm: a biological rhythm with a period (from peak to peak or trough to trough) of
about 24 hours; from the Latin circa, “about” and dies, “a day”
o Best-known circadian rhythm is the sleep-wake cycle, but there are hundreds of others
that affect physiology and performance
Ex. Body temperature fluctuates about one degree centigrade each day,
peaking, on average, in the late afternoon and hitting a low point, or tough in
the wee hours of the morning
Seasonal rhythms common. Birds migrate south in fall, bears hibernate in winter, and marine
animals become active or inactive depending on bimonthly changes in tides
In humans, female menstrual cycle occurs every 28 days on average
Biological rhythms influence everything from the effectiveness of medicines taken at different
times of day to alertness and performance on job
With better understanding of internal tempos, may be able to design out days to take better
advantage of our bodies’ natural tempos
Circadian Rhythms
Exist in plants, animals, insects, and humans
Reflect adaptation of organisms to many changes associated with rotation of Earth on axis such
as changes in light, air pressure, and temperature
External time cues abound, and people's circadian rhythms become entrained to them,
following strict 24-hour schedule
To identify endogenous rhythms, scientists must isolate volunteers from sunlight, clocks,
environmental sounds, and all other cues to time
o Some have spent weeks or even months alone in caves and salt mines, linked to outside
world by one-way phone line and cable transmitting physiological measurements to
o Now volunteers live in specially designed rooms equipped with stereo systems,
comfortable furniture, and temperature controls
o When participants have been allowed to sleep, eat, and work whenever they wished,
few have lived a “day” that is much shorter or longer than 24 hours. If allowed to take
daytime naps however, most participants live a day that averages about 24.3 hours
Commonly entrained to external time cues
Endogenous rhythm averages around 24.3 hrs
Removed from cues about 10% of people have clocks running slower and 10% running faster
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Increase in accidents at transition to daylight Saving Time
The Body’s Clock
Suprachiasmatic Nucleus (SCN): an area of the brain containing a biological clock that governs
circadian rhythms
o Located in tiny teardrop-shaped cluster of cells in hypothalamus
o Neural pathways from special receptors in back of eye transmit information to SCN and
allow it to respond to changes in light and dark. SCN then sends out messages that
cause brain and body to adapt to changes
Other clocks exist but SCN regarded as master pacemaker
Melatonin: a hormone, secreted by the pineal gland, that is involved in the regulation of daily
biological (circadian) rhythms
o When sleep in darkened room, melatonin level rises, when wake up to lightened room,
melatonin falls
Melatonin therapy used to treat insomnia and synchronize disturbed sleep-wake cycles of blind
people who lack light perception and whose melatonin production doesn’t cycle normally
When the Clock is Out of Sync
Internal Desynchronization: a state in which biological rhythms are not in phase (synchronized)
with one another
o Often occurs when people take airplane flights across several time zones
o Sleep and wake patterns adjust quickly but temperature and hormone cycles can take
several days
o Jet lag affects energy level, mental skills, and motor coordination
Occurs when worker must adjust to new shift. Efficiency drops, person tired and irritable,
accidents become more likely, sleep and digestive disorders may occur
May become matter of life and death for cops, emergency room personnel, airline pilots, truck
drivers, and operators of nuclear power plants
University of British Columbia research Stanley Coren studied records of all accidental deaths in
the US over a three-year period, found that the spring shift to daylight saving time (and the
minimal sleep loss associated with it) produced short-term increase in likelihood of accidental
death but the fall shift had little effect
Rotating night-shift assignments don’t allow worker’s circadian rhythms do resynchronize, can
help resynchronize by using melatonin or other techniques, not ready however
o Best approach is to avoid shifting as much as possible
Circadian rhythms not perfectly regular in daily life. Can be affected by illness, stress, fatigue,
excitement, exercise, drugs, mealtimes, and ordinary daily experiences. Even diet
Circadian rhythms differ greatly from individual to individual because of genetics
Moods and Long-Term Rhythms
Ecclesiastes “To everything there is a season, and a time for every purpose under the heaven.”
Does the Season Affect Moods?
Some people become depressed during particular seasons, typically winter, when periods of
daylight are short- known as seasonal affective disorder (SAD)
During winter months, SAD patients report feelings of sadness, lethargy, drowsiness, and a
craving for carbs
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To counter effects of sunless days, physicians and therapists have been treating SAD patients
with phototherapy, having them sit in front of bright fluorescent lights at specific times of the
day, usually early in the morning. Also prescribing antidepressants and other drugs
Approx. 2-3% of Canadian population suffers from SAD, US is less than 1% same with Europe,
Asian is 0-1%
Much more common in women, ratio about 2:1
When people with SAD exposed to either a brief period (about 30 minutes) of bright light after
waking or to light that slowly became brighter, simulating dawn, their symptoms were reduced
Concluded that SAD patients must have some abnormality in the way they produce or respond
to melatonin
One study, SAD patients produced melatonin for about half an hour longer at night in winter
than summer whereas control subjects showed no season pattern
Does the Menstrual Cycle Affect Moods?
First half, increase in estrogen causes lining of uterus to thicken in preparation for possible
pregnancy. Mid-cycle, ovaries release mature egg, or ovum. After, ovarian sac that contained
egg begins to produce progesterone- helps prepare uterine lining to receive egg. Then, if
conception doesn’t occur, estrogen and progesterone levels fall, uterine lining sloughs off as the
menstrual flow and cycle begins again
Question is whether these physical changes are correlated with emotional or intellectual
changes as folklore and tradition would have us believe
Most people think so, physical symptoms (fatigue, headache, irritability, and depression)
associated with the days preceding menstruation came to be thought of as an illness and was
given the label: “premenstrual syndrome” (PMS). Since then, most people have assumed,
uncritically, that many women “suffer” from PMS or its supposedly more extreme and
debilitating version, “premenstrual dysphoric disorder” (PMDD)
What does evidence actually show? Many women have physical symptoms associated with
menstruation, including cramps, breast tenderness, and water retention although women vary
tremendously. Physical symptoms can just make women grumpy or unhappy just as pain can
make men grumpy or unhappy
But emotional symptoms associated with menstruation (notably irritability and depression) are
pretty rare
Just like with SAD patients, more people claim to have symptoms than actually do
In reality, fewer than 5% of all women have such symptoms predictably over their cycles
Consciousness is the awareness of oneself and the environment. Changing states of
consciousness are often associated with biological rhythms- periodic fluctuations in
physiological functioning. These rhythms are typical entrained (synchronized) to external cues,
but many are also endogenous, generated from within even in the absence of time cues.
Circadian fluctuations occur about once a day; other rhythms occur less frequently or more.
When people live in isolation from all time cues, they tend to live a day that is just slightly longer
than 24 hours. Circadian rhythms are governed by a biological “clock” in the Suprachiasmatic
nucleus (SCN) of the hypothalamus. The SCN regulates, and in turn is affected by, the hormone
melatonin, which responds to changes in light and dark and which increases during the dark
hours. When a person’s normal routine changes, the person may experience internal
Desynchronization, in which the usual circadian rhythms are thrown out of phase with one
another. The result may be fatigue, mental inefficiency, and an increased risk of accidents
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