UNIT 2: Biological Bases of Behavior
PART II: States of Consciousness
Learning Targets
16-1 Describe sleep as a state of consciousness.
16-2 Describe how our biological rhythms influence our daily functioning.
16-3 Describe the biological rhythm of our sleeping and dreaming stages.
16-4 Explain how biology and environment interact in our sleep patterns.
16-5 Describe sleep’s functions.
What is sleep?
a periodic, natural loss
of consciousness — as distinct
from unconsciousness resulting
from a coma, general anesthesia,
or hibernation
(Adapted from Dement, 1999.)
What is the circadian rhythm?
Our bodies roughly
synchronize with the 24-hour cycle of day and night thanks to an internal biological clock
called the circadian rhythm (from the Latin circa, “about,” and diem, “day”).
Circadian rhythms impact our sleep-wake cycles, temperature, hormonal and digestive cycles as well.
How does the circadian rhythm affect �our daily functioning?
Body temperature rises as dawn nears, peaks during the day, dips in the afternoon then drops again in the evening.
Thinking and memory improve as we approach our daily peak in circadian arousal.
Age and experience may alter our circadian rhythm.
1. What Would You Answer?
Which of the following represents a circadian rhythm?
How do psychologists research biological rhythms that occur during sleep?
EEG records brain wave activity while sleeping.
Varying wave patterns occur during sleep.
What are alpha waves?
When you are in bed with your eyes closed, the researcher in the next room sees on the
EEG the relatively slow alpha waves of your awake but relaxed state. Then you slowly enter sleep.
Moving into sleep.
We seem unaware of the moment we fall into sleep, but someone watching our brain waves could tell.
(Dement, 1999)
What are the two divisions of sleep stages?
NREM sleep
non-rapid eye
movement sleep; encompasses all
sleep stages except for REM sleep
REM sleep
rapid eye movement
sleep; a recurring sleep stage during which vivid dreams
commonly occur
What is NREM -1 stage sleep?
During this brief NREM-1 sleep you may experience fantastic images resembling hallucinations.
You may have a sensation of falling or floating weightlessly. Sometimes a leg or arm may jerk.
These hypnagogic sensations may later be incorporated into your
memories.
What is NREM -2 stage sleep?
You then relax more deeply and begin about 20 minutes of NREM-2 sleep, with its periodic
sleep spindles — bursts of rapid, rhythmic brain-wave activity, and K-complexes.
Although you could still
be awakened without too much difficulty, you are now clearly asleep.
What is NREM -3 stage sleep?
During this slow-wave sleep, which
lasts for about 30 minutes, your brain emits large, slow delta waves and you are hard to
awaken.
Have you ever said, “That thunder was so loud last night!” only to have a friend respond, “What thunder?” Those who missed the storm may have been in delta sleep.
How do we move through the stages of sleep in a night?
Cycling through sleep stages is like being
on a roller coaster.
AP® Exam Tip
Study this cycle of sleep carefully.
One common mistake that students make is to believe that REM sleep comes directly after deep NREM-3 sleep.
As you can see, it does not.
Generally, NREM-2 follows NREM-3.
Then comes REM.
This clarification will help for the AP® exam.
What is REM sleep?
rapid eye movement
sleep; a recurring sleep stage during which vivid dreams commonly occur
REM is known as paradoxical sleep, because the muscles are relaxed (except for minor twitches) but other body systems are active.
How do researchers study REM?
Using an EEG, researchers were able to see that the sleeper’s eyes moved rapidly from left to right
while emitting rapid, saw-toothed brain waves.
What physiological events occur during REM?
Heart rate rises; breathing becomes
rapid and irregular.
Genitals become aroused, men may have an erection, women may experience vaginal lubrication.
Muscle paralysis occurs, except for an
occasional twitch.
2. What Would You Answer?
Shortly after falling asleep, James experiences the hypnagogic sensations of falling. It is most likely that he is in which stage of sleep?
B. NREM-1
C. NREM-2
D. NREM-3
How does sleep change as we age?
As people age, sleep becomes
more fragile, with awakenings
common among older adults.
(Kamel & Gammack, 2006;
Neubauer, 1999).
How do biology and environment interact in our sleep patterns?
Sleep patterns are genetically influenced, but they are also culturally influenced.
In Britain, Canada, Germany, Japan, and the United States, adults average 7 hours of sleep a night on workdays, 7-8 hours on other days.
(NSF, 2013)
Why do American students get less sleep than their Australian counterparts?
earlier school start times
increased extracurricular activities
lack of parent-set (and enforced) bedtimes
What three environmental factors play a role in our biological ability to sleep?
modern electric lighting
shift work
social-media diversions
What is the suprachiasmatic nucleus (SCN)?
a pair of cell clusters in the hypothalamus that controls circadian rhythm
In response to light, the SCN causes the
brain’s pineal gland to decrease its production of the sleep-inducing hormone melatonin in
the morning and to increase it in the evening thus modifying our feelings of sleepiness.
.
How does the SCN react during the day?
Light striking the retina signals the
suprachiasmatic nucleus (SCN)
to suppress the pineal gland’s
production of the sleep hormone
melatonin.
How does the SCN react at night?
At night, the SCN
quiets down, allowing the pineal
gland to release melatonin into the
bloodstream.
Would you rather be a brown bat or a giraffe?
What are sleep’s functions?
protection
At the end of the day’s hunting, gathering, and travel, our ancestors were better off asleep in a cave, out of harm’s way.
Those who didn’t wander around dark cliffs were more likely to leave descendants; natural selection!
recuperation
Sleep helps restore the immune system and repair brain tissue.
Sleep gives resting neurons time to repair themselves, while pruning or weakening
unused connections
What are more of sleep’s functions?
restoration and rebuilding
Sleep consolidates our memories by replaying recent learning
and strengthening neural connections.
feeds creative thinking
Dreams can inspire noteworthy artistic and scientific achievements.
A complete night’s sleep gives a boost to
our thinking and learning.
What are sleep’s other functions?
supports growth
During slow-wave sleep, which occurs mostly in the first half of a night’s sleep, the pituitary gland releases human growth hormone, which is necessary for muscle development.
3. What Would You Answer?
Which of the following sleep theories would best explain why athletes perform better after a full night’s sleep?
B. protection
C. growth
D. recuperation
Learning Target 16-1 Review
Describe sleep as a
state of consciousness.
Sleep is the periodic, natural loss of consciousness — as distinct from unconsciousness resulting from a coma, general anesthesia, or hibernation.
Learning Target 16-2 Review
Describe how our biological rhythms
influence our daily functioning.
Learning Target 16-3 Review
Describe the biological rhythm of
our sleeping and dreaming stages.
Learning Target 16-3 Review cont.
Describe the biological rhythm of
our sleeping and dreaming stages.
Learning Target 16-4 Review
Explain how biology and environment
interact in our sleep patterns.
Learning Target 16-5 Review
Describe sleep’s functions.