Module 34 - Sleep

Question 1

What is the behavioral definition of sleep?

Answer 1

Defined behaviourally: normal suspension of consciousness.

Question 2

What is the electro-physiological definition of sleep?

Answer 2

• Defined electro-physiologically: Specific brain wave criteria (a series of precisely controlled physiological states)
  
  • Governed by brainstem nuclei

Question 3

How much does sleep consume our lives?

Answer 3

Sleep consumes ⅓ of our lives

Question 4

Is sleep well understood?

Answer 4

Most of the details about sleep are poorly understood but its clinical importance is obvious
I.e. acute/chronic lack of sleep can interfere with daily activities

Question 5

Why do we sleep? Animals are particularly vulnerable while sleeping… must have a considerable advantage.

Answer 5

• Replace glycogen levels
• Colder at night (efficient energy expenditure)
• Humans and other animals are dependants on vision/light
• Memory consolidation

Question 6

True or false: the adverse effects of lack of sleep are well documented.

Answer 6

TRUE

Question 7

What happens when you don’t sleep?

Answer 7

Sleep deprivation can lead to reduced cognitive function (problem solving and memory) and concentration.

Question 8

What are some of the specific brain regions that are known to be particularly vulnerable to sleep deprivation?

Answer 8

…“specific brain regions involved with certain neurocognitive domains, including executive attention, working memory, and higher cognitive functions, are known to be particularly vulnerable to sleep deprivation.”

Question 9

Explain the example of medical residents and how it is proof to what happens when you don’t sleep.

Answer 9

• Residents are more likely to have a motor vehicle crash or “near miss” after a night of on-call duty, or after a shift lasting 24 hours or longer.
• Sleep-deprived residents also have more attention lapses, experience more adverse events, and make more diagnostic errors while on duty overnight.

Question 10

What is sleep debt?

Answer 10

Sleep debt or sleep deficit is the cumulative effect of not getting enough sleep. A large sleep debt may lead to mental or physical fatigue. There are two kinds of sleep debt: the results of partial sleep deprivation and total sleep deprivation.

Question 11

Does sleep debt need to be repaid very quickly?

Answer 11

YES, right away

Question 12

Is fatigue a cause more vehicle accidents?

Answer 12

Yes

Question 13

How is sleep across the lifespan?

Answer 13

• Most adults sleep for ~8 hours
• Infants and teenagers sleep more
• Older adults sleepless

Question 14

Why do OT’s and PT’s care about sleep?

Answer 14

• OT = “Restful and adequate sleep provides the foundation for optimal occupational performance, participation, and engagement in daily life, a concept that is historically consistent with the development of occupational therapy.”
• PT = “Participation in an exercise training program has moderately positive effects on sleep quality in middle-aged and older adults. Physical exercise could be an alternative or complementary approach to existing therapies for sleep problems.”

Question 15

What are circadian (once per day) rhythms?

Answer 15

• Most people sleep for ~ 8 hours a day, which is regulated by our circadian rhythm = to sleep once a day.
• Circadian rhythms are physical, mental, and behavioral changes that follow a daily cycle. They respond primarily to light and darkness in an organism’s environment. Sleeping at night and being awake during the day is an example of a light-related circadian rhythm.

Question 16

True or false: Most people sleep for ~ 7 hours a day.

Answer 16

False: Most people sleep for ~ 8 hours a day.

Question 17

You could potentially start sleeping at any point in the 24-hour cycle… So, how do we know when to sleep?

Answer 17

• Photoentrain: (synchronize) physiological processes with the day-night cycle
• “Biological clock” must be able to detect decreases in light levels as night approaches
  
  • Both of these aspects = maintain daily rhythms in spite of the variable amount of daylight & darkness in different seasons + different locations on the planet.

Question 18

What is the suprachiasmatic nucleus (SCN)

Answer 18

• “Master Clock”
• Specialized cells in ganglion layer of the retina contain melanopsin
• These cells convey information about environmental light levels information to the suprachiasmatic nucleus - located in the hypothalamus
• The SCN ultimately activates the pineal gland, modulating the production of melatonin.
• Melatonin in the bloodstream modulates SCN activity re: sleep/wake cycles
• Less light = more melatonin

Question 19

What type of cells conveys information about environmental light levels information to the suprachiasmatic nucleus?

Answer 19

Specialized cells in ganglion layer of the retina contain melanopsin

Question 20

Where is the suprachiasmatic nucleus located?

Answer 20

In the hypothalamus

Question 21

The SCN ultimately activates the _______________, modulating the production of ______________.

Answer 21

The SCN ultimately activates the pineal gland, modulating the production of melatonin.

Question 22

What modulates SCN activity re: sleep/wake cycles?

Answer 22

Melatonin in the bloodstream

Question 23

True or false: More light = more melatonin

Answer 23

False → Less light = more melatonin

Question 24

What is the history of the stages of sleep?

Answer 24

• For many years, “we” though sleep was uniform (i.e. the same from start to finish)
• Passive physiology for physical and mental restoration
• In the mid-1950’s we learned that sleep has stages
• EEG recordings showed at least four stages of sleep

Question 25

What are the stages of (non-REM) sleep? (don’t need to know more detail than what is on the image)

Answer 25

IMAGE

Question 26

What are some characteristics of stage I of sleep?

Answer 26

Reaction to stimuli from the outside world diminish “Had just fallen asleep or had been in the process of doing so.” Stray thoughts and short dreams

Question 27

What are some characteristics of stage II of sleep?

Answer 27

Unlikely to react to light or a noise, unless it is extremely bright or loud. Nearly 50 % of the total sleep time spent in this stage.

Question 28

What are some characteristics of stage III of sleep?

Answer 28

* Truly deep sleep. * Little response to external stimuli unless very strong or have personal meaning (e.g. fire alarm, your name, your baby crying)

Question 29

What are some characteristics of stage IV of sleep?

Answer 29

* The deepest stage of non-REM sleep. * Lowest neuronal activity. * Sleepwalking and night terrors. * Most of the body’s repair work * Muscle tone, heart rate, breathing, metabolic rate, body temperature and blood pressure are all decreasing through the stages and are at the lowest in stage IV.

Question 30

Nearly 50 % of the total sleep time is spent in this stage. Which sleep stage is it?

Answer 30

Stage II

Question 31

Which stage is the deepest stage of non-REM sleep and has the lowest neuronal activity?

Answer 31

Stage IV

Question 32

Which stage is the “truly deep sleep”?

Answer 32

Stage III

Question 33

Muscle tone, heart rate, breathing, metabolic rate, body temperature, and blood pressure are all decreasing through the stages and are at the lowest in stage \_\_\_\_\_\_\_?????

Answer 33

Muscle tone, heart rate, breathing, metabolic rate, body temperature, and blood pressure are all decreasing through the stages and are at the lowest in stage IV.

Question 34

What are the stages of cyclical sleep?

Answer 34

* ~60 minutes of non-REM sleep = stage I - IV * Followed by ~10 minutes of REM sleep * Then the cycle repeats * Over the course of a night, roughly four additional periods of REM sleep occur - each longer than the last.

Question 35

Over the course of a night, roughly ______ additional periods of REM sleep occur - each longer than the last.

Answer 35

Over the course of a night, roughly four additional periods of REM sleep occur - each longer than the last.

Question 36

How much time are you in a non-REM sleep during the sleep cycle?

Answer 36

~60 minutes

Question 37

How much time are you in REM sleep during the sleep cycle?

Answer 37

~10 minutes BUT as the cycle repeats, we get longer REM sleep periods, each longer than the last.

Question 38

What are some of the characteristics of REM sleep?

Answer 38

* Relatively high neuronal activity * Almost as much as during wakefulness * The physiological state is in sharp contrast with sleep stages 1-4 * Positive effects on immune function * Lower proportion of REM sleep in older adults(?) → decrease in immune function * Memory consolidation * High prevalence of dreaming

Question 39

True or false: REM sleep neuronal activity is almost as much as during wakefulness.

Answer 39

True! Relatively high neuronal activity = Almost as much as during wakefulness The physiological state is in sharp contrast with sleep stages 1-4

Question 40

In which sleep stage is there a high prevalence of dreaming?

Answer 40

REM sleep

Question 41

In which sleep stage is there memory consolidation?

Answer 41

REM sleep

Question 42

How does a lower proportion of REM sleep in older adults affect their immune function?

Answer 42

* A decrease in immune function * Therefore, we know that REM sleep has positive effects on immune function

Question 43

If REM sleep is almost like we are awake, then why don’t we act out our dreams?

Answer 43

We don’t act out our dreams: The reason we dont is because the sensory input and motor output are inhibited during sleep

Question 44

What is our sensory input and motor output inhibited by, during sleep?

Answer 44

It is done through dopamine

Question 45

What happens when we have dopamine antagonists

Answer 45

There is less dreaming

Question 46

What happens when we have dopamine agonists

Answer 46

There are more intense dreams

Question 47

What are the theories of why do humans sleep?

Answer 47

* Restorative theories * Replenish brain glycogen levels * Tissue growth and repair * Energy conservation theory * Metabolic demands are lower during sleep * Brain plasticity theory * Memory consolidation * Infant brain development → perhaps the reason why infants sleep so much is that their brain is developing at such a high rate * “Impaired sleep has been associated with Alzheimer’s disease. Studies suggest that sleep plays a role in clearing beta-amyloid out of the brain.”

Question 48

What is the restorative theory of why we sleep?

Answer 48

Replenish brain glycogen levels Tissue growth and repair

Question 49

What is the energy conservation theory of why we sleep?

Answer 49

Metabolic demands are lower during sleep

Question 50

What is the brain plasticity theory of why we sleep?

Answer 50

* Memory consolidation * Infant brain development → perhaps the reason why infants sleep so much is that their brain is developing at such a high rate

Question 51

Is impaired sleep associated with Alzheimer’s disease?

Answer 51

“Impaired sleep has been associated with Alzheimer’s disease. Studies suggest that sleep plays a role in clearing beta-amyloid out of the brain.” In Alzheimer’s disease, there are these beta-amyloid plaques that build up, so these are typically cleared out with sleep

Question 52

What is the connection between sleep and memory?

Answer 52

* Consolidation originates from reactivation of recently encoded neuronal memory representations, which occur during slow-wave sleep and transform respective representations for integration into long-term memory. Ensuing REM sleep may stabilize transformed memories. * Our brain plays things over when we are sleeping, and REM sleep may stabilize recently transformed memories.

Question 53

What is the connection between sleep and health outcomes - particularly cardiovascular outcomes?

Answer 53

Both short and long duration of sleep is predictors, or markers, of cardiovascular outcomes. [coronary heart disease, stroke, cardiovascular disease]

Question 54

True or false: Too little OR too much sleep has negative cardiovascular outcomes

Answer 54

True

Question 55

True or false: Increased sleep is correlated with decreased mood

Answer 55

False: Decreased sleep is correlated with decreased mood