AP Biology class blog for discussing current research in Biology

Tag: biological clock

Clock Change is Actually Great For Your Brain!

November this year, our clocks went back an hour, which accelerated the arrival or darker evenings and seemingly “shorter days”. It doesn’t actually make the days any shorter, in merely just shifted an hour of available daylight from the evening to the morning. Most people take lighter evenings as a priority over lighter mornings, arguments are always made over the benefits for easier travel in lighter evenings from clock changes. However, research suggests that holding onto lighter mornings could give more advantages. Having light in the morning, instead of any other time of the day, leads significant brain-boosting results. In fact, it helps us to function much better.

Early Morning

Credit: Attribution license: Porsche Brosseau


All living animals and plants on Earth revolve their lives around the 24-hour cycle of light and dark. For humans, we desire to sleep during the dark night, and our bodies are honed to environmental light via a biological chain reaction. 

We, humans, detect light intensity by special cells in the retina, then the information is relayed to the internal body clock in the brain, called the suprachiasmatic nucleus. It is in the hypothalamus (which uses the endocrine system to regulate internal body processes), which is linked to hormone secretion, through the pituitary gland. These light messages’ job is to internalize information about light intensity in the surrounding environment.

The chain reaction continues with the brain driving the secretion of the hormone cortisol for a specific time of the day, it is in low levels in the dark and high levels in the light. Cortisol is a very important hormone that has very dramatic effects on the human brain and body. The cortisol is also known as the “Stress hormone” that keeps us healthy through its 24-hour pattern.

The cortisol awakening response(CAR) occurs the first 30 minutes of waking up, it is a strong burst in cortisol secretion. The lighter the mornings, the bigger the CAR. Which directly results in a better functioning brain throughout the day. In an experiment, people who have greater seasonal depression, stress, anxiety and lower arousal exhibited the lowest winter CARs. But when they are exposed to artificial light during their awakenings, their CAR was restored. Thus proving that morning light is the most effective treatment for the winter blues.

Other research has also shown that CAR in the morning is directly linked to better brain plasticity, better goal-setting, decision-making and executive function.

The burst of cortisol secretion in the morning sweeps throughout the entire body where it is recognized by receptors on all body cells. The receptors then generate the biological chain reaction to allow us to function better for the day ahead. A lack of light in the morning can make us feel not functioning fully, and an exposure to light in the morning is extremely beneficial.


Scraping Your Knee at 12:00am vs. Scraping Your Knee at 12:00pm: What’s the Difference?

By the time you reach the age of five, you’ve probably scraped your knee more times than you can count. Now, think back to the last time you fell off your bike or stubbed your toe during the day and the last time you did the same at night. Do you remember a difference? Chances are, you weren’t paying close enough attention, but there are scientists who were, and they have come to an interesting conclusion. According to a new study from England, nighttime injuries take longer to heal than daytime injuries, 60% longer to be exact! Why? It all has to do with the biological clock and the 24-hour cycle of cardiac rhythms of skin cells.

The Healing Process

Fibroblast skin cells are found in the deepest layer of the skin called the dermis. Check out the picture on the left for a close up view! When an injury occurs, fibroblasts travel to the surface of the skin, where their job is to synthesize and build the structural support of the new skin. How fast the fibroblasts travel to the surface depends on the time of day and the biological clock. Actin, a protein that forms the supportive structure of the cytoskeleton and gives a cell its shape, is the reason behind this difference. Ned Hoyle, a molecular biology researcher, studied the changes in actin over time, and came to the following conclusion: during the daytime, actin is in the form of long filaments, while at night, actin is in globular form. Actin filaments are crucial in helping cell moves, so when actin is in globular form, it takes longer for the fibroblast cells to travel to the surface of the skin.

The Evidence

The team of researchers conducted experiments on mice, which exhibited the same affect they had studied previously – the healing time at night is longer than during the day. Next, the team turned to humans, studying burn patients. From hospital records, they concluded that on average, burns that occurred during the day healed within 17 days, whereas burns that occurred at nigh healed within 28 days. However, there are still a lot of unknowns. Scientists predicted that the fibroblasts would make up for lost ground during the day, but in reality, the cells wounded during daytime never catch up.

What’s Next?

Although we can’t plan when we get hurt, this research is extremely important. Hoyle said that this research could be expanded to trying to make cells think its daytime, if a procedure takes place at night. Furthermore, he hopes to conduct more research on the complex process of healing and blood clotting. To check out their full study, click here!

Waking up without the alarm clock? There’s a reason!


Have you ever wondered why you wake up before your alarm clock?

This article explains how new studies show that humans do have a special biological clock that allows us to wake up in the morning. This “clock” gets our metabolism going early in the day, the signal to wake up our bodies.  The important part of this biological clock is a protein called PERIOD (PER).  This protein rises and falls in our bodies throughout a 24 hour cycle. When PER lowers at night, our heart rate slows, our blood pressure lowers, and our mental processes slow down.  Now, through studies funded by Salk’s Innovation Fund, it is found an enzyme helps raise the PER protein once again in the morning.  This enzyme, JARID1a, is required for normal cycling, including the circadian rhythm.

Have your grandparents ever wondered why they can not sleep at night as well anymore?  Findings show that as you grow older, your biological clock declines, and with it, a difficulty in sleeping.

Even diabetes has been linked to this research.  Diabetes goes in turn with the biological clock, which controls its metabolic cycles.  The conversion of fats and sugars only take place at certain times of the day.  With someone who has diabetes, this suggests that the biological clock has lost control.

Numerous times I have woken up before my alarm clock, frustrated about not getting those extra few minutes of sleep.  Now, through this study, I understand that its my bodies’ protein levels telling my metabolism to start the day.

For more information on your biological clock, click here.


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