Internal and External Influences on Sleep

Internal and External Influences on Sleep

Circadian Rhythms

Circadian means around a day- these are human body rhythms that have a 24 hour cycle- such as body temperature, hormonal changes or the sleep wake cycle.

Circadian rhythms are controlled by the SCN (superchiasmatic nucleus), which is a pair of small nuclei found in the hypothalamus. The SCN is set by external triggers such as light.

Ultradian Rhythms

These are cycles that are below 24 hours- such as the sleep cycle (5 cycles of 4 90 minute stages). Others are also appetite, blood circulation and heart rate. These can affect the sleep wake cycle, for example appetite- we may wake when hungry.

Body Temperature

Body temperature is synced with the sleep wake cycle (both controlled by the superchiasmatic nucleus)- it rises at the end of sleep, and drops when we are ready to sleep and in the afternoon.

SLEEP-WAKE CYCLE

This is a 24 hour cycle controlled by the superchiasmatic nucleus that sets when we are awake and asleep. It is set by external cues like time and light.

• Jet lag- this is a disruption to our sleep wake cycle and happens because we change time zones. This means…