The Sleep-Wake Cycle
Many things in nature are cyclical. Our bodies are no different.
We, too, operate on natural cycles, one of them being the sleep-wake cycle. This rhythmic function of the body is operated by an internal clock located in a specific part of the brain.
With regards to sleep, this part of the brain is regulated by the daily rising and setting of the sun, which triggers the release of chemicals and hormones that either make us sleepy as darkness falls or wake us up with the sunrise. Scientists call this rhythm "circadian," Latin for "around a day."
A disruption of this natural cycle may make it difficult to fall asleep.