Have you ever noticed that you start feeling sleepy at about the same time every night? This is an example of your sleep-wake cycle. Your body moves in a fairly regular pattern between sleepiness and alertness.

Your sleep-wake cycle is managed in your brain by two different functions:

• Circadian rhythms. Your circadian rhythms manage the timing of your wakefulness and sleep over a 24-hour period. This is affected by the amount of light and darkness around you, among other things.
• Homeostatic sleep drive. Your sleep drive manages the amount of pressure you feel to sleep. The longer you're awake, the more your sleep drive "pressures you" to sleep. In other words, it makes you feel sleepy.

These functions work in the background of your brain 24 hours a day. They interact with each other and balance each other. For example, if you usually go to bed at 11 p.m., as that hour gets closer, your circadian rhythms send you signals about going to bed. But if you slept until noon that day, your homeostatic sleep drive would tell your brain that you still have some rest and energy in you. You don't need to sleep now.

When the circadian rhythms and homeostatic sleep drive are working well together, people have regular sleep-wake cycle schedules and little difficulty falling or staying asleep. Of course, certain factors can affect how well these processes work together — certain health conditions, exposure to light, medications, job and family responsibilities. Your daily habits play one of the biggest roles.

You can help these two natural processes work together by sticking with a regular sleep schedule. Go to bed and get up at the same time every day of the week, even when it's "a day off" from your usual routine. People who follow a regular sleep pattern tend to sleep better.

Many effective treatments for insomnia focus on changes you can make, without medications, to bring your circadian rhythms and homeostatic sleep drive back into sync.