Sleep is your built-in nightly “systems update.” The hypothalamus schedules the downtime, the brainstem enforces it, and every 90 minutes you cycle through distinct “software modules” (NREM 1 → NREM 2 → NREM 3 → REM) that patch memory, clear toxins, and reboot mood. Nail the architecture below and Unit 2 questions become free points.
1. Circadian Framework
| Piece | What It Does | Key AP Facts |
|---|---|---|
| Suprachiasmatic Nucleus (SCN) (in hypothalamus) | Master clock; light → SCN → ↓melatonin (pineal) | Lesion = random sleep–wake; jet-lag disrupts SCN rhythm |
| Pineal Gland | Releases melatonin | Melatonin peaks ≈ 2 AM; suppressed by blue light |
| Zeitgebers | External “time-givers” (light, meals) | Realign circadian phase after travel |
2. Stages of Sleep — The 90-Minute Ultradian Cycle
| Stage | Brain Waves (EEG) | Quick Function Tag | Classic Features |
|---|---|---|---|
| NREM-1 | Theta; hypnagogic | Light entry | Hallucinations, myoclonic jerk |
| NREM-2 | Theta + sleep spindles & K-complexes | “Data-back-up” | 50 % of total sleep; spindles aid memory consolidation |
| NREM-3 (Slow-wave) | Delta (0.5–2 Hz) | Physical repair | Growth hormone release; night terrors, sleepwalking |
| REM | Sawtooth beta-like | Cognitive reboot, dreaming | Muscle atonia, paradoxical sleep; consolidates procedural/ emotional memory |
Cycle trend: First half-night rich in N3; second half tilts toward REM.
3. Sleep Functions (Why Your Brain Pays the Power Bill)
Restoration: Tissue growth, immune boost (NREM-3).
Memory Consolidation: Hippocampus “replays” -> cortex (N2 & REM).
Growth & Development: Pituitary GH surge in deep sleep.
Cognitive Housekeeping: Glymphatic system clears β-amyloid (slow-wave).
Emotion Regulation: REM dampens amygdala hyperactivity; mood reset.
4. Sleep Disorders Cheat Grid
| Category | Disorder | Hallmark | AP Hook |
|---|---|---|---|
| Dyssomnias | Insomnia | Trouble falling/ staying asleep | CBT-I > pills (test likes treatments) |
| Narcolepsy | REM “attacks,” cataplexy; low orexin | Treated w/ stimulants | |
| Sleep Apnea | Airway collapse → snore, O₂ drop | Daytime fatigue despite “sleep” | |
| Parasomnias | Night Terrors | Screams, no recall, NREM-3 | Diff from nightmares (REM) |
| Sleepwalking (Somnambulism) | Complex motor acts, NREM-3 | Mostly children | |
| REM Sleep Behavior Disorder | No atonia → act out dreams | Predictor of Parkinson’s |
5. Dream Theories Snapshot
| Theory | Core Claim | Support / Critique |
|---|---|---|
| Freud – Wish Fulfillment | Manifest vs. latent content masks unconscious drives | Little empirical support |
| Activation-Synthesis (Hobson & McCarley) | Brainstem bursts → cortex weaves story | Explains bizarreness |
| Information-Processing | Dreams sort & fix the day’s memories | REM ^ following intensive learning |
| Physiological | REM keeps neural pathways “oiled” | Infants (lots of REM) building circuits |
10 AP-Style Multiple-Choice Questions
Sleep spindles are most characteristic of which stage?
A. NREM-1 B. NREM-2 C. NREM-3 D. REM E. Wake alphaImmediately after light hits the retina at night, which sequence reflects the pathway that delays sleep onset?
A. Retina → SCN → pineal gland ↑melatonin
B. Retina → pineal gland ↑melatonin → SCN
C. Retina → SCN → pineal gland ↓melatonin
D. Retina → pons → pineal gland ↑melatonin
E. Retina → thalamus → pineal gland ↓melatoninDelta waves indicate that a sleeper is most likely in:
A. REM dreaming B. Stage 2 C. Stage 3 D. Hypnagogic hallucination E. Paradoxical sleepNarcolepsy involves sudden intrusion of REM physiology during wakefulness due to deficiency of:
A. Melatonin B. Serotonin C. Dopamine D. Orexin (hypocretin) E. AcetylcholineAfter running a marathon, people often experience increased time in NREM-3. This best supports which sleep theory?
A. Freudian wish fulfillment B. Restoration C. Activation-synthesis D. Physiological neural exercise E. Information-processingWhich disorder is correctly paired with its primary sleep stage?
A. Nightmares — NREM-3
B. Sleepwalking — REM
C. REM Behavior Disorder — REM
D. Night terrors — REM
E. Sleep apnea — NREM-1With each successive 90-minute cycle through the night, the proportion of time spent in REM generally:
A. Decreases steadily B. Increases steadily C. Remains constant D. Disappears after first cycle E. Mirrors NREM-3 exactlyThe glymphatic system, responsible for clearing metabolic waste from the brain, is most active during:
A. Light sleep (N1) B. Slow-wave sleep C. REM sleep D. Quiet wakefulness E. Sleep onset onlyElectroencephalogram (EEG) recordings show rapid, irregular waves accompanied by muscle paralysis. Which conclusion is most accurate?
A. The sleeper is about to awaken from Stage 2.
B. The sleeper is in REM sleep.
C. The sleeper is experiencing a night terror.
D. The sleeper is in deep slow-wave sleep.
E. The sleeper is transitioning through N1.Cognitive-behavioral therapy for insomnia (CBT-I) primarily targets:
A. Increasing melatonin secretion pharmacologically
B. Restructuring maladaptive thoughts and habits around sleep
C. Stimulating the SCN with phototherapy
D. Inducing parasympathetic dominance via benzodiazepines
E. Surgically enlarging the airway
Answer Key & Rationale
| # | Ans | Why It’s Right | Key Distractor Note |
|---|---|---|---|
| 1 | B | Stage 2 marked by spindles & K-complexes. | C features delta; D sawtooth REM. |
| 2 | C | Light → SCN signals pineal to suppress (↓) melatonin. | A reverses direction. |
| 3 | C | Delta = deep NREM-3 slow-wave. | A & D = REM; B stage-2 theta. |
| 4 | D | Orexin deficit causes narcolepsy; stim drugs mimic orexin. | Others not central. |
| 5 | B | Physical exertion → body repair (restoration theory). | D refers to REM neural-exercise. |
| 6 | C | REM Behavior Disorder ≈ acting out dreams (REM without atonia). | B reversed; D night terrors N3. |
| 7 | B | REM bouts lengthen toward morning. | A applies to N3. |
| 8 | B | Glymphatic clearance peaks in slow-wave. | C lower flow due to atonia. |
| 9 | B | REM = fast EEG + paralysis (“paradoxical”). | C night terrors occur N3. |
| 10 | B | CBT-I = cognitive restructuring + sleep hygiene, stimulus control. | A/E medical; C light ok for circadian but not CBT-I focus. |
Free-Response Questions
FRQ 1 — Sleep Deprivation Case (7 pts)
Prompt:
Sara, a high-school senior, sleeps ~4 hours on weeknights prepping for the AP exam. She reports mood swings, difficulty remembering material, and microsleeps in class.
Using psychological concepts,
a) Explain three cognitive or physiological consequences of chronic sleep deprivation that Sara is likely experiencing.
b) Propose two evidence-based strategies (not medication) to improve her sleep quantity and quality, referencing sleep theory where relevant.
High-Scoring Answer Elements
Impaired memory consolidation (1 pt): Lack of REM/N2 disrupts hippocampal-cortical transfer → poor retention.
Emotional dysregulation (1 pt): Amygdala hyper-reactivity; PFC control weakened → mood swings.
Reduced immune function / slower metabolism (1 pt): N3 deficit lowers growth hormone → increased illness risk.
Microsleeps (1 pt): Brain forces brief N1/REM episodes → attention lapses.
Strategy 1 — Sleep hygiene & regular schedule (1 pt): Consistent bedtime trains SCN; aligns circadian rhythm.
Strategy 2 — Power naps ≤ 30 min before 3 PM or strategic distributed practice to shift study earlier (1 pt): Restores alertness, leverages memory consolidation.
Link to theory (1 pt): Restoration & information-processing theories justify why improved N3/REM boosts exam performance.
FRQ 2 — REM vs. NREM Functions (7 pts)
Prompt:
Discuss three distinct functions attributed to REM sleep and two distinct functions attributed to NREM-3 sleep. For each function, cite one supporting empirical finding or real-world observation.
High-Scoring Answer Outline
| Stage | Function (pts) | Supporting Evidence (pts) |
|---|---|---|
| REM | 1. Procedural memory consolidation | Post-skill-training ↑ REM; REM deprivation impairs performance (1+1). |
| 2. Emotional regulation | fMRI: REM decreases next-day amygdala reactivity; PTSD shows REM fragmentation (1+1). | |
| 3. Neural development | Infants spend 50 % in REM; deprived rat pups show synaptic deficits (1+1). | |
| NREM-3 | 1. Physical restoration / GH release | Peak GH secretion during slow-wave; athletes ↑ N3 after exercise (1+1). |
| 2. Glymphatic waste clearance | Xie et al. 2013: 60 % ↑ interstitial space during N3 flushes β-amyloid (1+1). |
(Total 7 pts)
Rapid Review Mantras
“Spindles = Stage 2.”
“Delta = Deep Repair.”
“Paradox + Dreams = REM.”
“First half N3, second half REM.”
“Orexin out? You’re narco knocked-out.”
Sleep – One-Page Power Cheat Sheet 💤⚡️ | AP Psychology online course
| Stage / Feature | EEG Wave | Key Purpose | Signature Clues | AP Pitfall to Dodge |
|---|---|---|---|---|
| NREM-1 | Theta | Gateway / drift | Hypnagogic images, jerk | Don’t call it deep! |
| NREM-2 | Theta + Sleep spindles & K-complexes | Memory “save file” | 50 % of night | Spindles ≠ REM! |
| NREM-3 (Slow-wave) | Delta | Body repair, growth hormone, glymphatic clean-up | Night terrors, sleepwalking | Nightmares happen in REM, not here. |
| REM (Paradoxical) | Fast, saw-tooth β-like | Dreaming, emotion reset, procedural memory | Muscle atonia; cycles lengthen toward morning | Brain active, body frozen—know the paradox. |
Circadian Control 101
SCN (hypothalamus) – master clock → tells pineal to drop or stop melatonin.
Light → SCN → ↓ melatonin → wakeful; darkness reverses.
Zeitgebers = light, meals, exercise (jet-lag fixes).
Must-Know Disorders
| Dyssomnia | Parasomnia |
|---|---|
| Insomnia – CBT-I preferred over pills. | Night Terrors – N3, no recall. |
| Narcolepsy – low orexin; REM attacks. | Sleepwalking – N3, children. |
| Sleep Apnea – airway collapse; CPAP. | REM Behavior Disorder – acts out dreams, a Parkinson’s red flag. |
Five Quick Truths to Tattoo
Spindles = Stage 2; Delta = Stage 3.
First half-night → N3 heavy; second half → REM heavy.
All dreams can happen anywhere, but vivid narrative dreams = REM.
Slow-wave clears β-amyloid (brain “dishwasher”).
Strength of stimulus to stay awake? Orexin keeps the gate—narcolepsy lacks it.
Micro-Mnemonics
“BRAD” – Beta (awake) → Relaxed Alpha → Drowsy Theta → Deep Delta
“Spindle-2” – Sleep spindles live in Stage 2.
“Night Terror ≠ NightMare” – Terror = N3; Mare = REM.
Exam Hack: If you see delta waves, growth hormone, or bed-wetting → pick NREM-3. If the question says paradoxical, atonia, vivid dreams → that’s REM.