Sleep

Question 1

What measurements are included in a polysomnogram (sleep study)?

Answer 1

EEG (brain)
EOG (eye movement)
EMG (muscle activity)
ECG/EKG (heart)
Airflow
Oximeter (blood oxygen).

Question 2

What are the main EEG wave types and their frequencies?

Answer 2

Beta (β): 13–30 Hz
Alpha (α): 8–13 Hz
Theta (θ): 3.5–7.5 Hz
Delta (δ): < 4 Hz

Question 3

What EEG activity corresponds to different sleep stages?

Answer 3

Awake: Alpha & Beta
Stage 1: Theta, light sleep, may feel awake
Stage 2: Sleep spindles & K-complexes
Stage 3: Delta waves <50% of the time
Stage 4: Delta waves >50% of the time
SWS (Stages 3 & 4): Brain recovery
REM: Beta & Theta, vivid dreams, muscle paralysis

Question 4

What characterizes REM sleep?

Answer 4

Active brain (Beta/Theta)
Rapid eye movement
Paralysis (loss of muscle tone)
Genital arousal
Narrative dreams

Question 5

What is the typical progression of sleep stages through the night?

Answer 5

Repeats in ~90-minute cycles: NREM (1–4) → REM → Repeat, with REM periods getting longer later in the night.

Question 6

Which neurotransmitters and brain areas are involved in arousal?

Answer 6

Acetylcholine: Basal forebrain, Pons (active in waking/REM)
Noradrenaline: Locus coeruleus (vigilance)
Serotonin: Raphe nuclei (locomotion, cortical arousal)
Histamine: Tuberomammillary nucleus (wakefulness)
Hypocretin (Orexin): Lateral hypothalamus (sustains wakefulness)

Question 7

What is the role of the vlPOA?

Answer 7

Ventrolateral preoptic area inhibits arousal systems via GABA; essential for initiating sleep.

Question 8

What is the sleep-wake flip-flop mechanism?

Answer 8

Mutual inhibition between the vlPOA and arousal systems allows quick and stable transitions between sleep and wakefulness.

Question 9

What areas regulate REM sleep transitions?

Answer 9

REM ON and REM OFF areas mutually inhibit each other.
REM ON area activates:

EEG (via basal forebrain)
PGO waves (via Lateral Geniculate)
Eye movements (via tectum)
Muscle paralysis (via magnocellular nucleus)

Question 10

How does adenosine influence sleep?

Answer 10

Built up by astrocyte activity
Promotes SWS and delta waves
Inhibited by adenosine deaminase (G/A genotype = slower breakdown → more SWS)

Question 11

How does the body stay awake under threat?

Answer 11

Hunger and stress activate arousal systems via hypocretin, noradrenaline, and stress-related hormones like CRF from the amygdala.

Question 12

What is the role of the SCN in sleep?

Answer 12

Suprachiasmatic Nucleus (SCN) acts as the body’s master clock, organizing the sleep-wake cycle via:

vSPZ → DMH → Inhibits vlPOA & excites LH (orexin)

Question 13

How do Per, Cry, Clock, and Bmal1 regulate circadian rhythms?

Answer 13

Clock/Bmal1 proteins activate Per/Cry genes → proteins inhibit Clock/Bmal1 → 24-hour feedback loop

Question 14

How does light reset the biological clock?

Answer 14

Direct: Melanopsin-containing retinal ganglion cells → SCN
Indirect: Retina → LGN → SCN
Mechanism: Glutamate release → NMDA receptor → ↑ intracellular Ca²⁺ → ↑ gene transcription

Question 15

What is the role of melatonin in sleep regulation?

Answer 15

Released from pineal gland at night, inhibited by SCN during the day; feeds back to SCN and synchronizes body rhythms.

Question 16

What are some common sleep disorders?

Answer 16

Insomnia: Often overestimated, worsened by pills
Sleep Apnea: Breathing stops, sleep disrupted
Narcolepsy: Linked to hypocretin deficiency; includes sleep attacks, cataplexy, paralysis, hallucinations
REM Behavior Disorder: No paralysis during REM; act out dreams
SWS Disorders: Sleepwalking, night terrors, bedwetting, sleep eating
Jet Lag: Internal clocks out of sync; treat with melatonin