Sometimes you wake up extremely tired, other times you just can’t fall asleep. That post lunch slump kicks in and you feel like you’ve been kicked out. What does it all mean?

Everyone’s body runs on an internal “body clock”, according to the National Sleep Foundation. This rhythm is known as the circadian rhythm, and it explains why at certain times of the day you feel very tired or very awake. The circadian rhythm can be changed, and this is why some people can sleep through the entire morning, while others can’t make it past ten at night.

The body clock is controlled by a group of cells in the brain known as the suprachiasmatic nucleus. These cells gather information from light and darkness, and they tell your body how it should be feeling.

12:00-3:00 a.m.

At this time, the body is generally deep in sleep. Levels of attention are at their lowest levels and the body is waiting for dimmed lights and a comfortable place to lie down. That just makes you yawn, doesn’t it?

3:00-6:00 a.m.

The body is still asleep, but melatonin (the chemical that causes sleepiness) levels are going down. At this time, your body temperature is generally lower than it will be at any other point in the day. The body is working on rejuvenating itself, i.e. this is your beauty sleep.

6:00-9:00 a.m.

This is the best time for you to wake up. Around this time, the body has stopped producing melatonin and is getting ready for the day. It is best to get into bright lights to wake yourself up faster.

9:00 a.m.-12:00 p.m.

Your mind should be at or near its peak alertness at this time. If not, you probably are not getting enough sleep or you don’t have a good diet. However, a snooze period is coming up in the body clock.

12:00-3:00 p.m.

Because you have probably just eaten lunch, the body is ready for a siesta. A large amount of digestion is occurring in your body and it wants to take a nap. Your attention span is going to be lessened and your alertness is low.

3:00-6:00 p.m.

Your body is back on an upswing. This is the best time of day to exercise because your internal temperature is at its peak and your heart and lungs are ready to go.

6:00-9:00 p.m.

Your body is dipping back down after its peak. As a healthy bedtime approaches, it is suggested to avoid a larger meal because sleeping on a full stomach leads to the food consumed turning into fat, due to the lack of exercise past this point.

9:00 p.m.-12:00 a.m.

This is the best time to go to sleep. The body has started to produce melatonin again and your body is once again becoming drowsy. The internal temperature is dropping and in order to feel rested and refreshed in the morning, it is time to hit the hay.

Mitch Hopkins is a News Editor for the Patriot and jcpatriot.com