Circadian Cycles in Relation to Humans

By: Sophia Wang

On March 15, the Senate voted unanimously for the Sunshine Protection Act, a new law that would make daylight saving time permanent beginning on November 5, 2023. One of the biggest supporters of this new law is the retail industry. Stores believe that shoppers will spend more if it is light out later. The lawmakers regard the turning back of the clock as a morale killer.

Time is crucial. Even our physiological functions are controlled by biological clocks that complete one cycle every day. These cycles are called circadian rhythms after the Latin for “about” (circa) and “day” (dies).

In 1972, scientists discovered what controlled the cycle. The structure in an area of the brain’s hypothalamus (a region of the forebrain below the thalamus ) called the suprachiasmatic nucleus that coordinates with hormones and can be connected to increases and decreases in blood pressure. Over the years, researchers have found out that the human body has multiple clocks, including in most of our cells.

When most people think of circadian rhythms, they think of sleep cyclesl, but our body clocks also control our hunger, body temperature, our moods and our energy. Almost all of our cells have a group of genes that keep time internally. The clock genes cycle through their functions and then deactivate or activate other genes to go in daily patterns. This discovery surprised many because until then, it was believed that thirty percent at most of our genome was influenced by circadian rhythm. Another discovery found that 50 percent of our genes were controlled by the clock genes, either indirectly or directly.

“It was very hard to accept,” de la Iglesia, who is also the president of the Society for Research on Biological Rhythms, told me recently, recalling their conversation. “I love the idea, because I’m a circadian biologist. But it’s hard to believe.”

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