t n e m n o r i v n e r u o d n a s e v l e s r u o and handheld. What matters is not where your free hand is; it
matters where your attention is.
Sle•p aBiological rhythms
• Occur on a 24- hour cycle and include sleep and wakefulness. Termed
our “biological clock” it can be altered by artificial light.
• Light triggers the suprachiasmatic nucleus to decrease (morning)
melatonin from the pineal gland and increase (evening) it at nightfall.
Measuring sleep: about every 90 minutes, we pass through a cycle of 5 distinct
sleep stages, which researchers identify by measuring brain activity, eye
movements, and muscle tensions.
The major characteristics of the sleep stages ***
AWAKE BUT RELAXED when an individual closes his or her eyes but remains
awake, brain activity slows down to large amplitude and slow, regular ALPHA
STAGES 1-2 During early, light sleep the brain enters a high amplitude,
slow regular waveform called THETA waves. A person who is DAYDREAMING
shows theta activity.
STAGES 3-4 During the deepest sleep, brain activities slow down. There
are large amplitude waves, slow DELTA WAVES.
STAGE 5 After reaching the deepest sleep stage (4), the sleep cycle starts
moving backward towards stage 1. Although still asleep, the brain engages in
low- amplitude fast and regular BETA WAVES, much like awake- aroused state.
(the brain is awake but the body is asleep) (the most vivid dreams, but not the
only place where dreams can occur) DREAMS can occur in ANY sleep stage, but the most vivid dreams are reported
in STAGE 5 (REM stage). During this stage, you are essentially paralyzed. The
brain stem blocks messages of the motor cortex.
Why do we sleep?
THE EFFECTS OF SLEEP LOSS
- Thanks to Thomas Edison’s BRIGHT IDEA, we sleep less than our
ancestors. Teens, for example, need 8-9 hours per night but average
1. Impaired concentration
y t i l i b a t i r r i y l l a n o i t o m E . 2
m e t s y s e n u m m i d e s s e r p e D . 3
y t i l i b a r e n l u v r e t a e r G . 4
h t a e D . 5
Insomnia A persistent inability to fall asleep or to stay asleep.
Narcolepsy Overpowering urge to fall asleep that may occur while standing
up or talking
Sleep Apnea Failure to breathe when asleep
FatalFamilialInsomnia An extremely rare disease that prevents a person
from sleeping, resulting in death