Physiology of Sleep

Question 1

What is - a natural periodic state of rest for the mind and body - in which eyes usually close and consciousness is completely or partially lost, so there is a decrease in bodily movement and responsiveness to external stimuli?

Answer 1

Sleep

Question 2

How much of our lives is spent sleeping?

Answer 2

Approx 1/3

Question 3

Are sleeping patterns uniform for everyone?

Answer 3

No - some people need more sleep, some less.

Question 4

How does old age impact on sleep?

Answer 4

Sleep can become fragmented in old age - thought to attribute to various ailments as we get older.

Question 5

How can a lack of sleep impact on a person?

Answer 5

Can lead to significant impact on physiological as well as psychological well being - inc. affecting memory, temper, language and sense of time.

Question 6

How can we measure sleep?

Answer 6

Questionnaires

Physiological measurements - e.g. EEG, using biomarkers

Question 7

What is wrong with the questionnaire approach to assessing sleep?

Answer 7

Subject to interpretation by P, increased levels of error due to bias

Question 8

Why are physiological methods better for measuring sleep quality?

Answer 8

They are free from base and have reproducible results.

Question 9

Which method involves recording a gross average of electrical potentials of cells and fibres in the brain area close to an electrode?

Answer 9

EEG

Question 10

Which method involves recording a gross average of electrical potentials of cells and fibres in the brain area close to an electrode?

Answer 10

EEG

Question 11

What does EEG stand for?

Answer 11

Electroencephalography

Question 12

How does an EEG work?

Answer 12

Neurones generate electric potentials in the brain - some positive, some negative. The electrode on the scalp works out the sum total of charge in that area and reports it on a graph = brain waves

Question 13

How many neurons are usually detected by one electrode?

Answer 13

About 10,000

Question 14

What happens to the brain when there is no stimulus?

Answer 14

The neurons form a rhythmic pattern = synchronous rhythm on the EEG

Question 15

What are the basic requirements for signal detect?

Answer 15

Neurons must be active in synchrony to generate large enough electrical field to be detected from the scalp

Neurons must be aligned in parallel orientation - so they summate rather than cancel out

Question 16

What does amplitude of the EEG signal depend on?

Answer 16

Number of active cells, total amount of excitation & timing of activity

Question 17

How does an awake brain appear on EEG

Answer 17

Irregular rhythm, high frequency but low amplitude waves

Question 18

How does an asleep brain appear on EEG?

Answer 18

Regular rhythm, with low frequency and high amplitude waves

Question 19

Why do brain waves appear even when neurons are not being stimulated?

Answer 19

Thalamic cells = voltage-gated ion channels - self-discharge at rhythmic intervals even in the absence of external input.

Thalamic pacemaker neurons become synchronised via cellular and chemical communication. = Regular pattern on EEG

Question 20

Which ions passthrough thalamic pacemaker neurons?

Answer 20

Na, K & Ca

Question 21

What are the functions of brain rhythms when asleep?

Answer 21

We dont know

Question 22

How does increased, synchronised activity appear on EEG?

Answer 22

As larger amplitude waves

Question 23

What physiological responses occur when we are asleep?

Answer 23

Decreased in HR, RR & brain activity

Question 24

What behavioural changes occur when we are asleep?

Answer 24

Lack of gross movement

Rapid Eye movement cycles

Question 25

How many sleep cycles do we experience during the night?

Answer 25

6-7

Question 26

What are the stages of sleep?

Answer 26

Awake Stage 1 - NREM Stage 2 - NREM Stages 3-4 NREM REM

Question 26

What are the stages of sleep?

Answer 26

Awake Stage 1 - NREM Stage 2 - NREM Stages 3-4 NREM REM

Question 27

Name the stages of sleep on this EEG

Answer 27

Question 28

How many stages of non-rem sleep are there?

Answer 28

4

Question 29

What identifies Stage 1 NREM (N1)?

Answer 29

Irregular, jagged, low-voltage waves. Brain activity is high - but starts to decline

Question 30

What identifies Stage 2 NREM (N2?)

Answer 30

Sleep Spindle and K-complex presence

Question 31

What is the sleep spindle?

Answer 31

A frequency of 12-14 Hz burst for at least 500ms.

Question 32

What is the sleep spindle? What is it generated by?

Answer 32

A frequency of 12-14 Hz burst for at least 500ms Generated by oscillating interactions between the thalamus and the cortex

Question 33

How can you identify the K-complex? What is it caused by?

Answer 33

Is a sharp high-amplitude positive wave followed by a smaller slow negative wave. Occurs randomly and in response to auditory stimuli. Brain is responsive to the stimuli and monitors but doesn't necessarily wake up from it

Question 34

How can you identify stages 3 & 4 of NREM sleep?

Answer 34

Have δ waves = slow, large amplitude, regular waves

Question 35

What are stages 3&4 of NREM sleep known as?

Answer 35

Slow-wave sleep (SWS)

Question 36

At which stage of sleep can sleepwalking, nightmares and bed wetting occur?

Answer 36

Stages 3&4 NREM

Question 37

How does REM sleep appear on EEG?

Answer 37

Irregular, low voltage fast waves (similar to Stage 1).

Question 38

What happens during REM sleep?

Answer 38

Increased brain activity - may be because of dreaming

Question 39

Which sleep cycle is most important to awake rested?

Answer 39

REM

Question 40

How many stages of REM sleep do you get a night?

Answer 40

5-6

Question 41

Which stage is the brain most active and the body the least active in?

Answer 41

REM sleep

Question 42

What happens when you transition from NREM to REM sleep?

Answer 42

You awake slightly before entering REM sleep

Question 43

What physiological changes occur during REM sleep?

Answer 43

Postural muscles become more relaxed HR, RR & BP are more variable than other stages Increased blood supply to reproductive organs

Question 44

How long does the entire sleep cycle last?

Answer 44

90-120 mins

Question 45

Humans cycle from Stage 1 to REM during the first cycle of sleep. What happens in subsequent cycles?

Answer 45

Subsequent cycles start from stage 2 to REM every 90-110 mins

Question 46

Which drugs are best for inducing sleep?

Answer 46

Benzodiazepines

Question 47

How do benzodiazepines work?

Answer 47

Are GABA A modulators - modulate the Cl channel - allowing it to stay open longer - thus hyper polarising the cell = induction of sleep.

Question 48

How do benzodiazepines affect the sleep cycle?

Answer 48

Increase N1 & N2 but decrease N3&4 and REM sleep

Question 49

What is a big problem with benzodiazepines?

Answer 49

Dependance

Question 50

What are the limitations of the EEG?

Answer 50

No sensitive enough to pick up individual APs Cannot distinguish between excitation, modulatory or inhibitory activity Limited anatomical specificity

Question 51

Which scan is best for anatomical specificity of brain waves? What is its drawback?

Answer 51

fMRI best Very expensive

Question 52

Which hormones are involved in circadian rhythm?

Answer 52

Cortisol (day) and Melatonin (night)

Question 53

How does the circadian clock work?

Answer 53

Is present in the brain - receives information from light and regulates production of melatonin and cortisol, controlling sleep cycle. Also sets the peripheral clocks.

Question 54

What things are controlled by the peripheral circadian clocks?

Answer 54

Excretion, digestion, urination - synchronise internal organs

Question 55

Name 2 types of NREM parasomnias

Answer 55

Sleepwalking Night Terrors

Question 56

Name one type of REM parasomnias

Answer 56

Sleep Behavioural Disorder

Question 57

What is a sleep-related disorder called?

Answer 57

Parasomnia

Question 58

What disorder is this? P gets out of bed whilst still asleep, exhibits limited awareness and responsiveness to surroundings

Answer 58

Sleep walking (NREM)

Question 59

What disorder is this? P often screams in sleep - most are not responsive to outside stimuli and have no recollection of the source for their terror upon waking.

Answer 59

Night Terrors (NREM)

Question 60

What disorder is this?

Answer 60

Unusual vocalisations or movements during REM sleep,