schlafen

Schlafen is the German infinitive meaning to sleep; in German, Schlafen refers to the act of sleeping, while the noun Schlaf denotes sleep.

Sleep is a periodic, reversible state of diminished wakefulness, accompanied by characteristic brain activity, muscle relaxation, and altered sensory responsiveness. In humans, sleep cycles through non-rapid eye movement (Non-REM) stages 1-3 and rapid eye movement (REM) sleep, each cycle lasting about 90 minutes. Most adults complete 4-6 cycles per night and require about 7-9 hours of sleep to function well.

Sleep is regulated by circadian rhythms driven by the brain’s master clock in the hypothalamus, particularly the suprachiasmatic nucleus, and synchronized to environmental cues such as light. Melatonin release increases in darkness, promoting sleep onset.

Functions of sleep include restoration of tissues, brain plasticity and memory consolidation, energy conservation, and support for immune and metabolic processes. Adequate sleep supports cognitive performance, mood regulation, and long-term health.

Sleep varies by age and individual factors. Infants and young children need longer sleep than adults; older adults often experience lighter, more fragmented sleep. Common disorders include insomnia, obstructive sleep apnea, narcolepsy, and restless legs syndrome, which can disrupt sleep.

Research on Schlafen intersects neuroscience, psychology, and medicine, focusing on sleep architecture, its regulation, and the consequences of sleep disruption.