Chapter 11: Sleep & Waking

Question 1

Biological Rhythms

Answer 1

Internal biological clock

Multiple rhythms can be expressed within a single system—e.g., LH serum levels

Question 2

Ultradian

Answer 2

–Less than 24h

–Exp: activity

Question 3

Circadian

Answer 3

–Approximately 24h
–Exp: sleep-wake cycle

Any rhythmic change that continues at close to a 24 hour cycle in the absence of external cues (e.g., light/dark)
–body temperature
–cortisol secretion
–sleep and wakefulness

In the absence of time cues, the cycle period in humans lasts approximately 24.2 to 24.9 hours.

Question 4

Entrainment

Answer 4

is the process of resetting the biological clock

Question 5

zeitgeber

Answer 5

“time-giver”

The stimuli that an organism uses to synchronize with the environment

Question 6

Free-running Rhythm

Answer 6

Entrainment is the process of resetting the biological clock

The stimuli that an organism uses to synchronize with the environment is called a zeitgeber–“time-giver”

Question 7

Suprachiasmatic nucleus (SCN)

Answer 7

–Pacemaker of circadian rhythms.
–Incorporates more 2-deoxyglucose during light period.
–Electrically more active during light period of cycle.
–Rhythmic in the absence of inputs/outputs—i.e., it’s intrinsic.

Question 8

Origin of Internal Clock

Answer 8

Oscillations of protein production and degradation serves as the “ticking” of the internal clock Light participates in triggering some of these protein fluctuations

per: period
tim: timeless
Clock: circadian locomotor output cycles kaput.

Question 9

How Is The Clock Entrained?

Answer 9

Circadian rhythms entrain to light–dark cycles using different pathways, some outside of the eye.
Amphibians and birds have photoreceptors in the brain and pineal gland.
In mammals, light information goes from the eye to the SCN via the retinohypothalamic pathway.

Question 10

Retinohypothalamic Pathway (RHT)

Answer 10

The RHT consists of retinal ganglion cells that project to the SCN.
These non-image forming (NIF) ganglion cells do not rely on rods and cones.
Most of these retinal ganglion cells contain the photopigment melanopsin (blue light).

Question 11

Biochemistry of Circadian Rhythms

Answer 11

Body temp and awareness positively correlated.
Growth hormone is released during deep sleep.
Cortisol release is highest in the morning and drops during the day.

Question 12

Melatonin Entrainment

Answer 12

Melatonin is the hormone of darkness; released by pineal gland

Question 13

Disruption of Circadian Rhythms

Answer 13

Melatonin is the hormonal signal that entrains physiological systems to the “correct” circadian rhythm

Disruption of circadian rhythms, and melatonin signaling, by unnatural zeitgebers can lead to sleep disorders.
–Jet lag
–Daylight savings time
–Light pollution

Question 14

Jet Lag

Answer 14

Fatigue, irritability, and sleepiness result from a conflict between internal clock and external zeitgebers.
Adjustment easier when traveling east to west—go to bed later but can also sleep in later.

Question 15

Daylight Savings

Answer 15

Phase shift: shift in activity in response to a synchronizing stimulus (e.g., light/dark)

Spring shift is a phase advance
–Analogous to eastward travel
–7% increase in traffic accidents

Fall shift is a phase delay
–Analogous to westward travel
–7% decrease in traffic accidents.

Question 16

Artificial Light at Night

Answer 16

Shift work & Light pollution
–Increased cancer risk (prostate, breast)
–Linked to obesity and metabolic syndrome in animal models
–Circadian disruption or suppressed melatonin?

Question 17

Seasonal Affective Disorder

Answer 17

Causes
– Overproduction of melatonin
– Serotonergic system dysregulation
– Sleep phase delays

Treatment
– Phototherapy (< 10,000 lux)
– Antidepressants (SSRIs)

Question 18

Sleep / Wake Stages

Answer 18

There are 5 Stages of Sleep:
Stages 1-4 (SWS)
REM

There are 2 stages of Awake:
Alpha
Beta

Question 19

Beta rhythms

Answer 19

awake and alert;

15 to 20 Hz

Question 20

Alpha rhythms:

Answer 20

awake and relaxed;

8 to 12 Hz.

Question 21

Theta rhythm

Answer 21

4-7 Hz

Stage 1

Question 22

A typical night of sleep

Answer 22

Sleep time ranges from 7–8 hours.
45–50% is stage 2 sleep, 20% is REM sleep.
Cycles last 90–110 minutes, but cycles early in the night have more stage 3 and 4 SWS, and later cycles have more REM and stage 2 sleep.

Question 23

Sleep Across the Lifespan

Answer 23

?

Question 24

Functions of Sleep

Answer 24

Restorative
–Metabolism
–Energy expenditure

Adaptive
–Eating efficiency
–Vulnerability to predators

Question 25

Dreaming During REM and NREM

Answer 25

Dreams occur during both REM and NREM sleep.

Vivid dreams occur during REM sleep, characterized by:
–Visual imagery
–Sense that the dreamer is “there”

Dream Theories
–Hobson & McCarley: Activation Synthesis Theory
•Content of dream reflects ongoing neural activity.
–Crick & Mitchison – Forget irrelevant information.
–Winson – Integrate sensory experiences with memories.
–Reveonsuo: Threat simulation.

Question 26

Replay of Experience During Sleep

Answer 26

??

Question 27

Control of wakefulness

Answer 27

Reticular formation

• Helps maintain desynchronized activity in cerebral cortex
• Without input cortical neuronal activity becomes synchronized.

Locus coeruleus
-Releases norepinephrine

Anterior raphe nuclei
-Releases serotonin

Question 28

Reticular formation

Answer 28

Control of wakefulness

• Helps maintain desynchronized activity in cerebral cortex
• Without input cortical neuronal activity becomes synchronized.

Question 29

Locus coeruleus

Answer 29

Control of wakefulness

• Releases norepinephrine
• diverse and rich projections to many brain areas

Question 30

Anterior raphe nuclei

Answer 30

Control of wakefulness
-Releases serotonin
Diverse and rich projections to many brain areas

Question 31

Preoptic area of hypothalamus

Answer 31

Control of NREM sleep

• Inhibits wakefulness circuits.
• NREM-on cells.

Question 32

LC & RN

Answer 32

Control of NREM sleep

-Norepinephrine and serotonin release decreases, preparing brain for REM sleep.

Question 33

Control of REM sleep

Answer 33

REM-on area: rostral pontine reticular formation
-Responsible for rapid eye movement and muscle paralysis

REM-off areas: LC and RN

• Decrease before REM sleep dis-inhibits the pons
• After 30 min of REM the LC and RN reactivate, inhibiting pons

Question 34

REM-on area

Answer 34

rostral pontine reticular formation.

-Responsible for rapid eye movement and muscle paralysis.

Question 35

REM-off areas

Answer 35

LC and RN

• Decrease before REM sleep dis-inhibits the pons.
• After 30 min of REM the LC and RN reactivate, inhibiting pons.

Question 36

REM vs. Waking (top):

Answer 36

–Secondary visual cortex and limbic system more active during REM
–Prefrontal cortex less active during REM

Question 37

REM vs. SWS (lower):

Answer 37

–Most of the brain is more active during REM than during SWS.

Question 38

SWS

Answer 38

Slow Wave Sleep (Non-REM)

Question 39

Sleep Disorders

Answer 39

Dyssomnias: abnormality in the amount, quality or timing of sleep
–Insomnia
–Narcolepsy
–Hypersomnia

Parasomnias: abnormal behavior or physiology during sleep
–Nightmares
–Night terrors
–Somnambulism (sleepwalking)
–Restless leg syndrome

Question 40

Insomnia

Answer 40

People with insomnia may have
–Trouble falling asleep (“onset insomnia”)
–Many awakenings during the night, with difficulty going back to sleep (“maintenance insomnia”)
–Fitful sleep
–Sleep state misperception (“pseudo-insomnia”)

During the day, people with insomnia may be
–Drowsy
–Anxious and irritable
–Forgetful, with difficulty concentrating

Question 41

How common is insomnia?

Answer 41

More than half of adults in the U.S. said they experienced insomnia at least a few nights a week during the past year.
Nearly one-third said they had insomnia nearly every night.

• Increases with age.
• The most frequent health complaint after pain.
• Twice as common in women as in men.
• Treatment is either behavioral or pharmacological (sedatives).

Question 42

Somnambulism

Answer 42

sleepwalking

Occurs during deepest stages of Slow Wave Sleep.
They can be woken up without harm.

Question 43

Narcolepsy

Answer 43

Unwanted sleep attacks.

Symptoms:
- Excessive daytime sleepiness
- Cataplexy: sudden muscular paralysis while conscious
- Sleep paralysis: similar loss of muscle control during transition between sleeping & waking
Do not go through SWS before REM sleep
Genetic component: 1-2% among first-degree relatives
No known cure, only symptom relief.

Question 44

Hypersomnia

Answer 44

Characterized by excessive daytime sleepiness.
–Lack of or interrupted sleep at night.
–Nap frequently and inappropriately.
–Anxiety, irritation, restlessness, slower thinking, memory difficulty.
–Comorbid with many psychological disorders.

Question 45

REM Behavior Disorder

Answer 45

REM paralysis absent or minimized.
–Act out dramatic and/or violent dreams.
–Shouting and grunting.
–Voluntary muscles become tonic, or tensely contracted.

Question 46

How many times does a person cycle through the stages of sleep in a 8-hr night?

Answer 46

4-5 times