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