Chapter 6: Sleep Flashcards

Question

Suprachiasmatic nucleus (SCN)

Answer 1

- Biological clock in the hypothalamus that **regulates the timing & activity of the sleep–wake cycle** - Responds to light and communicates with the pineal gland to control melatonin production - Can operate independently but is also influenced by zeitgebers ## Footnote NOTE: The SCN, itself, does NOT sense light.

Answer 2

- **Hormone** secreted by **pineal gland in hypothalamus** - Influences **alertness, drowsiness & sleep-wake cycle** - ↓ light = more melatonin (induces drowsiness & sleep) - ↑ light = less melatonin (more alert) ## Footnote NOTE: Artificial light can be bright enough to delay melatonin release.

Answer 3

- **Light stimulates neurons in the eyes** (retina) which send **neural messages to the SCN** via the optic nerve - When no / low light is detected, the **SCN sends excitatory neural messages to the pineal gland** (results in the production and release of melatonin through bloodstream) - When light is detected, the SCN sends inhibitory messages to the pineal gland (results in suppression of melatonin)

Answer 4

- Allows the levels of melatonin in blood to be **monitored by SCN**

Answer 5

- Used to **treat sleep disorders** e.g. sleep onset insomnia - Generally safe for short-term use - Low likelihood of becoming dependent on its use

Answer 6

- **Shows sleep types & stages in relation to time** - Shows that NREM & REM sleep alternate in a cyclical way

Answer 7

- **Alternating sequence of NREM and REM** sleep periods - **N3 periods are followed by a climb back to REM** - **REM** progressively **lengthens** (dominant in 2nd half) - Shifting from light to deep sleep after sleep onset - Cycles last ~90 mins with the correct no. cycles (~4-5) - More deep sleep in the first half

Answer 8

- Makes up about **75–80% of our total sleep time** - Involves **3 stages** (sleep progressively becomes deeper) - Brain not as active compared to during REM sleep / NWC - Dominant in the first half of sleep

Answer 9

- **N1** – relatively **light sleep** (when sleep begins in 1st cycle) - ↓ 🫀 and 🫁 rate, body temp and muscle tension - Slow, rolling 👁 movements, **alpha-theta waves** - Involuntary muscle twitches (hypnic jerks) - Low arousal threshold; easy to wake - **N2** – **light / moderate sleep** (gradually becomes deeper) - Continued ↓ 🫀 & 🫁 rate, temp, muscle tension - 👁 movements stop, **theta-delta waves** present - Slightly ↑ arousal threshold but still easy to wake - Brief bursts of electrical activity (sleep spindles) - Makes up of most of NREM sleep - **N3** – **deep sleep** (low wave / delta sleep) - 🫀 and 🫁 rate slow to their lowest levels - Muscles are fully relaxed; we barely move - No 👁 movements, **delta waves** present - Highest arousal threshold; difficult to wake - Dominant in the first half of sleep

Answer 10

- About **half of a total sleep episode** is spent in **N2** - Evolutionary purpose for **safety** - Allows us to wake in response to potential threats

Answer 11

- **Onset** – transition period from being awake to asleep - **Latency** – amount of time it takes to transition from being awake to being asleep

Answer 12

- Makes up about **20-25% of our total sleep time** - Involves **spontaneous bursts of REM** (eyeballs move fast beneath closed eyelids in jerky, coordinated movements) - **Internal bodily functions** are **more active** compared to NREM (i.e. ↑ and more irregular 🫀 and 🫁 rate,↑ BP, etc.) - Yet, **externally**, the **body appears calm** and inactive - Dominant in the second half of sleep - Arousal threshold similar to N2 / N3

Answer 13

- **REM** - When most dreaming occurs - Tend to follow a narrative structure (realistic/fantasy) - **NREM** - Can be as bizarre as REM dreams - Tend to be shorter, less frequent & less structured - Less vivid and less likely to be recalled

Answer 14

- **REM Sleep** - EEG – beta-like waves (sawtooth pattern) - EOG – high activity (jerky, coordinated movements) - EMG – paralysis (no movement) - **NREM Sleep** - EEG – theta-delta waves (diff between N1, N2, N3) - EOG – slow, rolling movements / none - EMG – some movement

Answer 15

- Total **time spent asleep gradually ↓** as we age - Proportion of **REM sleep ↓ significantly during the first 2 years** and then remains relatively stable - Proportion of **NREM sleep ↓ through to old age**

Answer 16

- **Restoration theory** – sleep replenishes bodily resources - REM replenishes the mind, NREM replenishes the body - Growth hormone released during sleep (aids physical dev)

Answer 17

- **Poor sleep habits, hormonal changes, exposure to blue light and busy schedules** - Persistently getting poor quality / insufficient amounts of sleep can result in sleep dept (body & brain functions deteriorate)

Answer 18

- **At birth** – sleep onset begins at **REM** (any time; day/night) - 50% of sleep is REM and sleep duration is irregular - Because the circadian rhythm has yet to fully develop or sync with external cues (i.e. light / dark) - **By 3 months** – sleep onset begins at **NREM** - Circadian rhythm kicks in - Melatonin production becomes more cyclical

Answer 19

- Infants sleep for around 12-14 hours a day whereas adults sleep for around 6-7 hours a day - Infants’ sleep consists of ~50% REM and 50% NREM, whereas an adult would have ~20% REM and 80% NREM - Infants tend to sleep in multiple blocks of time and wake up frequently, whereas adults generally have one major sleep episode - Infants' sleep onset can begin at REM, whereas adults' sleep onset begins at NREM

Chapter 6: Sleep Flashcards

(45 cards)