Sleep and Wakefulness

Question 1

Compare

Awake, REM sleep and NREM sleep

Answer 1

Awareness, Cerebral Cortex active
Unconscious, Cerebral Cortex active, Paralysis of muscles
Unconscious, Cerebral Cortex inactive, reduced muscle tone

Question 2

Give all names of the sleep stages and which is higher proportion

Answer 2

N1 - Light sleep ‘transition’
N2

N3 - Slow Wave sleep - higher proportion of SW at the start

REM - higher proportion of REM at the end
Wakefulness

Question 3

Muscle activity across Stages

Answer 3

Tonic - N1 N2 N3 (w decreasing activity, N3 weakest)

REM - Paralyzed

Question 4

Eye activity across Stages + Wake

Answer 4

N1 - Decreased
N2 - NO Eye 
N3 - Delta activity from EEG
REM - Rapid eye movements
Wake - More than REM

Question 5

EEG Waves across Stages + Wake

Answer 5

N1 - decreasing alpha, increase theta (lower frequency) 4-7Hz
N2 - Theta; Sleep Spindles, K-Complexes
N3 - Delta (less than 4Hz)
REM - mixed frequency, Theta and Gamma; no alpha
Wake - Alpha, high freq (higher frequency) 8-12 Hz

So wavelengths go from

Alpha - Theta - Delta in decreasing frequency

Question 6

Neurochemistry involved in REM

Answer 6

Activating: Ach!
- although Ach is wake-promoting by inhibiting VLPO during wakefulness; it is present during REM

Ventrolateral preoptic nucleus // Arousal System

Inhibitory: Monoamines like Histamine, Serotonin, Norepinephrine

Question 7

Compare stages of sleep between young and old

Answer 7

Young: More REM, More Slow Sleep
Old: More awake, More Stage 1, 2,

Question 8

Describe and explain 2 biological factors affecting sleep timing

Answer 8

Homeostatic Sleep Drive: builds up during wakefulness

• could be partially due to adenosine
• adenosine build up awake, decrease when sleep
• adenosine then VLPO GABA

Circadian: 24hr sleep cycle in the body

• caused by projections from SCN to brain stem
• environmentally influenced by light, circadian photoreceptor Melanopsin involved

Question 9

Name sleep-promoting neuron in the anterior hypothalamus and its function

Answer 9

Ventrolateral Preoptic Nucleus, anterior hypothalamus

• produces GABA
• GABA is inhibitory; blocks wake-promoting areas
• activated by Adenosine and PG D2
• inhibited by Noradrenaline, Ach

Note wake-promoting and sleep-promoting have mutual inhibition;

Question 10

What 2 affects of somnogen PG D2

Answer 10

Increase GABA - inhibitory, sleep-promoting

Increase Adenosine - sleep-promoting

Question 11

Name highest functioning neuron types in awake and sleep

How about Ach? And Orexin

Answer 11

Awake: Monaminergic cell groups - Amines
Sleep: VLPN - GABA

Ach is high in awake, high in REM too but low in NREM
Orexin is Wake-promoting hence low in sleep
- orexin stabilizes arousal system

Question 12

Pathophysiology of Narcolepsy, Type 1

Answer 12

Lack of Orexin, wake-promoting, in the brain due to cell destruction

Question 13

Whats SCN function and what happens in SCN lesion

Answer 13

suprachiasmatic nucleus (SCN) - also in Hypothalamus
- Loss of circadian rhythm; projection to BS lost

Note SCN do not have projections to VLPO directly but still links to other GABA, sleep promoting neurons. (wiki)

Question 14

What is chronic snoring an indicator of

Answer 14

Obstructive Sleep Apnea

Question 15

Give symptoms of Narcolepsy

Answer 15

Excessive daytime sleepiness; frequent sleep attacks

• also increased waking up at night
• sleep paralysis

Cataplexy: sudden loss of muscle tone when awake

Question 16

Name the Inhibitory Neurotransmitters
Name the Arousal Neurotransmitters

their functions linking to VLPO and Arousal system

Answer 16

Sleep-Promoting

• Adenosine, PG D2
• GABA from Ventro-Lateral Preoptic Nucleus VLPO
• Activate VLPO and inhibit arousal system

Arousal, Wake-Promoting

• Orexin (may not be linked to VLPO)
• Monoamines: Histamine, Serotonin, Adrenaline
• Caffeine
• Ach
• Inhibit VLPO and activate arousal system

Acetylcholine is wake-promoting; also induces REM sleep