Sleep, Circadian Rhythms, and Sleep Disorders

Question 1

Where in the brain is the biological/circadian master clock?

Answer 1

The suprachiasmatic nucleus (SCN)

Question 2

What two “systems” provide the drive for sleep? What’s the take-home point about their interaction?

Answer 2

Circadian (SCN, light, etc.)
Homeostatic sleep need.
Sometimes you have a homeostatic sleep need, but you can’t sleep well because it’s not lined up with what you’re circadian system wants.

Question 3

What color of ambient light most promotes wakefulness?

Answer 3

Blue light. (it’s why it’s bad to look at computer screens at night)

Question 4

What’s the path for ambient light information to the pineal gland?

Answer 4

Retina -> retinohypothalamic tract -> SCN -> superior cervical ganglion -> pineal gland (for melatonin release, or not)

Question 5

What’s the main hormone telling you to go to sleep?

Answer 5

Melatonin

Question 6

What’s the main hormone telling you to wake up?

Answer 6

Cortisol.

Question 7

Is the SCN the only circadian rhythm clock in the body?

Answer 7

No. Every organ appears to have circadian rhythms, but they’re controlled to some extent by the SCN.

Question 8

Do people’s circadian rhythms ever adjust to night shift work?

Answer 8

Nope. Working at night produces additional sleep pressure that can’t be slept away because people have trouble sleeping during the daytime.

Question 9

6 elements of a polysomnography?

Answer 9

EEG
Eye movements
Muscle activity
EKG
Respiration
Behavioral activity

Question 10

3 important factors for full “recovery” during sleep?

Answer 10

Continuity (passing through the proper stages at the proper time)
Depth (getting to proper sleep stages)
Duration

Question 11

What is slow wave sleep (SWS)? What parts of the brain are synchronized?

Answer 11

Deep sleep. High amplitude, low-frequency brain waves.

Thalamo-cortical and thalmo-reticular connections are have slow oscillations.

Question 12

What does the EEG for REM sleep look like?

Answer 12

It looks like the person is awake, but the person is paralyzed.

Question 13

What’s a hypnogram? How does the beginning of the night differ from the end of the night?

Answer 13

Graph of different sleep stages and the time in which the patient is in them. People have more slow-wave sleep (SWS) early in the night, with more frequent bouts of REM before waking.

Question 14

Is muscle tone (except for the eye muscles) normal, or low during REM?

Answer 14

low

Question 15

Is muscle tone normal or low during slow wave sleep?

Answer 15

Normal.

Question 16

What might be the key “sleep switch?”

Answer 16

The VLPO - ventrolateral preoptic nucleus of the hypothalamus.

Question 17

Do newborns sleep less than adults?

Answer 17

Nope. They sleep a lot more, but they sleep in short, rapid cycles.

Question 18

What areas of the brain have been shown in PET scans to have less activity when sleep-deprived? (4 areas)

Answer 18

Thalamus, prefrontal cortex, inferior parietal lobe, occipital cortex.

Question 19

Clinically, if you have a patient who’s really sleep deprived, what’s an immediate concern you should address?

Answer 19

How are they getting home, i.e. will they be driving?

Question 20

What is “wake state instability” and how is it measured experimentally?

Answer 20

Wake state instability refers to stochastic variability in attention / response time that occurs when sleep-deprived.
It’s measured by recording latency when trying to press a button after a light blinks.

Question 21

Are people generally conscious of how poorly they perform when sleep deprived?

Answer 21

Nope.

Question 22

Can you still learn while sleepy?

Answer 22

Yes, but your cognitive speed is much lower.

Question 23

Should you ever stay up all night when you have a running sleep debt?

Answer 23

No. Your cognitive performance falls through the floor.

Question 24

Does everybody need the same amount of sleep / do poorly on little sleep?

Answer 24

No. Some people are very susceptible to missing sleep, some people barely perform worse at all when sleep deprived.

Question 25

Is the danger of residency more about working long hours or not getting enough sleep?

Answer 25

Not getting enough sleep.

Question 26

Are naps effective at increasing performance when sleep deprived?

Answer 26

Yep.