PSYB64 Chapter 11 Sleeping and Waking notes - UTSC
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Course
PSYB64 (PSYB64)
Institution
University Of Toronto (U Of T
)
Book
Discovering Behavioral Neuroscience: An Introduction to Biological Psychology
Detailed textbook chapter notes for Ch 11 Sleeping and Waking.
Freberg, L. (2018). Discovering Behavioral Neuroscience: An introduction to Biological Psychology. Cengage Learning.
Biorhythms
Circadian rhythm - A repeating cycle of about 24 hours.
Ultradian cycle - A cycle that occurs several times in a single day.
Zeitgeber - An external cue for setting biological rhythms.
Free-running circadian rhythm - A rhythm that is not synchronized to environmental time
cues.
Entrainment - The resetting of internal biological clocks to the 24-hour cycle of the earth's
rotation.
Individual Variations
in Sleep Patterns
- People who are most alert and productive in the morning have been referred to as "larks;'
whereas night people have been referred to as "night owls”. Many people fall somewhere
between these two extremes. Adults with the lark pattern demonstrate more positive
emotions and subjective well-being.
- Nearly everyone acts like an owl during adolescence. Teen sleep patterns might reflect a
dramatic drop in melatonin, one of the neurochemicals involved in the regulation of
sleep patterns, at the onset of puberty.
Shift Work, Jet Lag, and Daylight Saving Time
Shift maladaptation syndrome - A condition resulting in health, personality, mood, and
interpersonal problems resulting from sleep disruption due to shift work.
Jet lag - Fatigue, irritability, and sleepiness resulting from travel across time zones.
- Not all changes in time zone have equal effects. People adjust more readily when travel
or changes in shift work require staying up later and sleeping later. In other words, it is
easier to adjust to a phase-delay of our cycle (setting the clock to a later point) than to a
phase-advance (setting the clock to an earlier point).
- Jet Lag Is Worse When Traveling East => Traveling eastward is more disruptive than
traveling westward. The Los Angeles resident arriving in New York feels like he or she is
going to bed three hours earlier than usual (7 p.m. Los Angeles time) and waking up in
the middle of the night (3 a.m. Los Angeles time). The New Yorker traveling to Los
Angeles has to stay up a little later (1 a.m. New York time) but then can sleep later to
compensate (9 a.m. New York time). Most people find the latter scenario much easier.
, The Body's Internal Clocks Manage Circadian Rhythms
- The body's internal master clock is the suprachiasmatic
nucleus (SCN) in the hypothalamus; located above (supra) the
optic chiasm.
- Input to the SCN comes from axons of special cells known as
intrinsically photosensitive retinal ganglion cells
(ipRGCs), which leave the optic nerve and project to the SCN,
forming the retinohypothalamic pathway.
- The ipRGCs do not process information about visual images. The
ipRGCs contain a photopigment known as melanopsin that is
related to, but different from, the other photopigments involved in
vision.
- The SCN is active only during the day, activity in the human SCN
produces a response in the sympathetic nervous system, which in turn communicates
with the pineal gland.
- As light decreases in the evening, accompanied by reduced SCN activity, less input from
the sympathetic neurons allows the pineal gland to synthesize and release more
melatonin, a neurochemical that modulates brainstem structures related to waking and
sleep.
- The SCN also manages other sleep-related changes, including body temperature,
hormone secretion, production of urine, and blood pressure changes.
- The SCN is not dependent on input from other structures to maintain its rhythms.
Isolated SCN tissue cultures continued to show rhythmic fluctuations in activity
consistent with the source animal's previous day-night cycle. Transplants of SCN tissue
also support its role as a master internal clock.
THE CELLULAR BASIS OF CIRCADIAN RHYTHMS
- The ebbing and flowing of special circadian proteins require approximately 24 hours.
Research with fruit flies (Drosophila melanogaster) has allowed researchers to identify
three separate genes and their protein products that are involved with cellular circadian
rhythms.
- These genes and their proteins are per (for period), tim (for timeless), and Clock (for
circadian locomotor output cycles kaput).
- Together, per and tim proteins inhibit the Clock protein, whereas the Clock protein
promotes the production of more per and tim proteins.
- As levels of per and tim proteins increase, inhibition of the Clock protein ensures that no
further per and tim proteins will be produced.
- When levels of per and tim proteins drop over time, the reduced inhibition of the Clock
protein results in increased production of per and tim proteins. Neural activity reflects
the oscillation of the levels of these internal proteins, providing a mechanism for
communicating rhythms to other cells.
THE BIOCHEMISTRY OF CIRCADIAN RHYTHMS
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