PSY100H1 Chapter Notes - Chapter 11: Adenosine, Hypnopompic, Cataplexy

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25 Jan 2013
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Chapter 11 – Textbook Notes
Sleep and Waking
Circadian Rhythms
We follow many rhythms
Circadian Rhythm: Our daily cycle of sleep and waking (a cycle of 24 hours)
Zeitgeber: external stimuli or cue for setting biological rhythms (light, etc)
Light, physical activity, feeding, body temperature & sleep-related hormones
Internal biological clock + Zeitgeber = Circadian Rhythm
Free running circadian rhythm
not due to external cues
can last 24.2 to 24.9 hours.
Light helps us fo on the 24 hr clock in accordance w/ Earth's rotation
Variations in Sleep Patterns
Larks (morning person) vs. Owls (night person)
During adolescence, we all become temporary night owls ==> could be due to a drop in melatonin during
puberty.
Shift Work, Jet lag, and daylight saving time
Shift workers experience
1.5 less hrs of sleep than normal pple
Health problems
Interpersonal Problems
Carr Accident
Job Errors (Especially Nurses)
Breast Cancer risk
Jet Lag
Phase delay (fall) is easier than phase advance
Jet lag is worse when travelling east (you have to sleep earlier and get up earlier than you normally
would)
Phase advance = higher accident rate
Internal Clocks
Body's master clock ==> suprachiasmatic nucleus (SCN) in the hypothalamus (located above optic
chiasm)
Suprachiasmatic Nucleus (SCN)
Only active during the day (despite whether it's a night or morning animal)
Helps animals distinguish btwn day and night
Isolated SCN continues with its rhythm
SCN of original animal can be implanted into another animal and cause a change in that animal's
clock
Ex: An animal that ran on an 18 hr clock, when implanted with the SCN of an animal that ran on
a 24 hr clock, will now run on the 24 hr clock.
SCN is much quicker to adjust to phase shifts, then lungs, muscle, and then liver.
Rhythms of the SCN are heavily influenced by the presence of light
This makes sense because it's located near the optic nerve so it receives info abt environmental
light.
The Cellular Basis of Circadian Rhythms
How does SCN tell time?
It does it through production of proteins
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Clock protein produces per and tim. When per and tim increase to high levels, they inhibit the clock
protein from producing any more per and tim. This is usually throughout the day. Per and tim levels
decrease and are very low during the night. Low levels of per and tim then activate the clock to
produce more.
Biochemistry and Circadian Rhythms
2 hormones that affect sleeping: Melatonin & Cortisol
Melatonin (high levels = sleepiness)
Secreted by pineal gland
Regulated by the SCN
Low during the day and high during the night.
Peaks at 4.a.m ==> that's why it's hard to stay awake.
Cortisol (high levels = wakefulness)
High levels usually during the morning
Seasonal Affective Disorder
Reduced daylight affects those at higher latitudes
Low seratonin?
Could be due to disruptions in melatonin release
However, rates of SAD aren't high among Icelanders (maybe due to protective genetic factors?)
Stages of Wakefulness and Sleep
EEG provides a general measure of overall brain activity
2 broad types of brain activity
Desynchronous brain activity (WAKEFULNESS)
Independent action of many neurons ==> alertness
2 patterns of brain activity for wakefulness
1) Beta wave pattern
rapid, low amplitude wave
very alert
2) Alpha wave pattern
slower, more regular waves
relaxed, but awake
These two patterns (periods of alertness and relaxation during wakefulness) follow ultradian
cycles (90 to 120 min cycles)
Synchronous activity (SLEEP)
Neurons fire in synchrony ==> sleep
Sleep
NREM
Stage 1
Light; u can still wake up
theta wave
heart rate & muscle tension decrease
muscle jerks = myoclonia
Stage 2
sleep spindles (short bursts) & k-complex (unexpected noise)
Characterize stage 2
Stage 3
Halfway through, you should see delta waves
Stage 4
Delta waves
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