Sleep, the Sleep–Wake Cycle and Sleep Deprivation

Sleep is a period of altered or reduced consciousness. This lesson covers the purpose of sleep, the sleep–wake cycle, and the causes and effects of sleep deprivation.

1. Purpose of sleep

• Evolutionary — e.g. avoiding harm from nocturnal predators/accidents; conserving energy after daytime exertion.
• Restorative — e.g. restoring energy reserves, replenishing neurotransmitters, repairing and growing cells and muscles.

2. The sleep–wake cycle

Sleep is an example of a circadian rhythm (an approximately 24-hour cycle). It comprises three stages of non-rapid eye movement (NREM) sleep and one stage of rapid eye movement (REM) sleep, measured by electroencephalography (EEG).

3. Sleep deprivation

Sleep deprivation is a condition in which an individual achieves poor-quality or insufficient sleep to sustain normal functioning. Partial deprivation = insufficient quantity/quality of sleep; chronic deprivation = this continues for an extended period.

Causes: shift work, drugs, sleep environment, stressors.

Effects:

• Acute — mood, attention, reflex speed, vision.
• Chronic — heart disease, obesity, insomnia, anxiety.

4. Sleep hygiene

Techniques to improve sleep hygiene include managing electronic devices, keeping consistent sleep patterns, and creating a healthy sleep environment.

Work through these together.

Evolutionary or restorative?

For each proposed purpose of sleep, decide as a class which perspective it reflects:

• Allowing muscles and cells to repair and grow.
• Keeping us safe and inactive during dangerous night hours.
• Replenishing neurotransmitters.

Linking causes to effects

For a nurse working rotating day/night shifts in a noisy apartment, identify two likely causes of sleep deprivation and one effect of each:

Answer independently, using examination-style directive verbs.