Like clockwork, the human body resets itself each night. Circadian rhythms, or the internal clocks, control a slew of different cycles in the body, which include anticipating temperature change, night and day cycles, melatonin rate and plasma control. While these cycles occur at different intervals, they are all occurring whether or not the person knows it. However, Rebecca Prosser, associate professor of biochemistry and cellular and molecular biology, said the one cycle that everyone is aware of is the sleep cycle.

“All organisms have internal clocks that generate a 24-hour rhythm which are completely independent of the external environments,” Prosser said Friday, Sept. 28 at the UT Science Forum.

However, external factors can affect the way the clocks function, said Andy Mangrum, recent graduate in the biochemistry and cellular and molecular biology. Mangrum worked together with Prosser in circadian research. He said the processes of the internal clock are just like a watch.

“If you bought a watch at Wal-Mart, the watch itself would already be running, but it would not show the right time,” Mangrum said. “To get the right time you would need to set it. You would be the external environment that sets the clock.

“You are not the battery or the working parts of the clock. It is the same way with our bodies. Our bodies run on about a 24-hour cycle, and to get the right time they have to be set with the external environment.”

The part of the brain that controls the circadian rhythm is located in the suprachiasmatic nucleus.

“(The SCN) receives signals directly from the eye. … The optic nerve sends the signal into the SCN allowing the clock to receive light information,” Prosser said. Once the SCN receives the light signal it acts as the master oscillator for the rest of the body, Prosser said.

The oscillator begins at the brain where the circadian rhythm causes other cycles in the body to act and adjust to the external environment, she said. If the rhythm is altered in any way the rest of the body’s cycles are thrown off, she said. Some of the other cycles are the heart and its control over body temperature and blood pressure, and the stomach and its control over digestion.

But still one of the most noticeable systems the circadian rhythm controls is the sleep cycle, she said.

“Sleep is the one of the rhythms that we are most aware of…. The control of sleep itself is a very complex process that is strongly influenced by the circadian clock,” Prosser said. “The process of sleep is like a seesaw effect.” Sleep is divided into a dual system: the sleep system, which regulates length of sleep, and the circadian system.

Together they combine and work off each other to create the correct sleep cycle, she said.