Chapter 4 - Stages of Sleep Flashcards
Infradian rhythms
Biological rhythms with cycles longer than 24 hours (Eg. Menstrual cycle).
Circadian rhythms
Biological rhythms with cycles that occur on a 24 hour cycle (Eg. Sleep/wake pattern, alertness, body temperature etc.).
Ultradian rhythms
Biological rhythms with cycles shorter than 24 hours (Eg. REM/NREM cycles).
CHARACTERISTICS OF SLEEP AS AN ASC
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What % of sleep time is spent in NREM 1-4 and REM?
Stage 1 (NREM): 10% Stage 2 (NREM): 50% Stage 3 (NREM): 10% Stage 4 (NREM): 10% REM: 20%
On average, how many REM/NREM cycles does an adult have each night?
Six.
How long does each stage last?
1 NREM - About 5 minutes.
2 NREM - About 20 minutes.
3 NREM - Brief.
4 NREM - First is about 30 minutes, progressively gets shorter.
REM - First is about 10 minutes, progressively gets longer.
When do sawtooth waves occur?
REM.
When do hypnic jerks and the hypnogogic state occur?
Stage 1 NREM.
When does no eye movement occur?
Stages 3 and 4 NREM (and a bit of stage 2 NREM).
States the type of brainwaves in each stage of sleep.
1 NREM - Alpha being replaced by theta. 2 NREM - Theta. 3 NREM - Theta becoming delta. 4 NREM - Delta (slow-wave sleep). REM - Beta-like (irregular).
Heart and breathing rate in each stage of sleep?
1 NREM - Irregular.
2 NREM - Slower and more regular.
3 NREM - Slower and more regular.
4 NREM - Slow and regular (slowest and most regular of all stages).
REM - Increase and fluctuations (up and down); irregular.
Body temperature in each stage of sleep?
1 NREM - Normal. 2 NREM - Lower. 3 NREM - Lower. 4 NREM - Lowest. REM - Unregulated.
When are night terrors, sleepwalking and bedwetting likely to occur?
Stages 3 and 4 NREM.
When do nightmares occur?
REM.
Somnambulism
Sleep walking.
Night terrors
When a person wakes up (often screaming) in sheer terror but rapidly returns to sleep and has no recollection of the event the next morning.
- Is common in young children (3-6 years old).
Hypnogram
The graph which the REM/NREM cycle is plotted on.
Hypnogogic state
The relaxed state that occurs during the transition from being awake to being asleep.
Hypnic jerk
Involuntary muscle twitches that cause us to jolt.
Hypnopompic state
Period between being asleep and waking up, a time when the brainwaves are predominantly alpha waves. Hypnopompic (vivid) images are often seen during this phase.
Explain the Survival Theory of Sleep.
Suggests that organisms undertake periods of inactivity, or sleep, in order to enhance their chances of survival.
They do this by conserving energy and protecting themselves during periods of the day when they are most vulnerable.
Explain the Restorative Theory of Sleep.
Sleep allows us to recharge our bodies, recover from the physical/physiological work during the day and allows our bodies’ growth processes to function.
Evidence that supports Survival Theory?
- Small, vulnerable animals sleep less than large, resilient animals because they are constantly at risk of death.
- Sleep conserves energy.
- Sleep is less necessary for animals that need more food (Eg. Cows).
Evidence that supports the Restorative Theory?
- Growth hormone is released during sleep.
- Sleep increases immunity (Immune cells are released).
- Sleep consolidates memories.
- Prepares body for action the next day.
Criticisms of Survival Theory?
- Assumption that sleep is useful, but not essential (does not explain why we MUST sleep).
- Assumption that sleep is a way to hide from predators (sleeping can be dangerous).
Criticisms of Restorative Theory?
- Assumption that more sleep is needed when we are physically active (what about people in wheelchairs?)
- Assumption that body rests during sleep (During REM, energy is expended so protein synthesis is slowed).
