Circadian Rhythm: Drosphilia and Humans

Our circadian rhythm regulate how our body functions throughout the day. It is one of our fundamental rhythms that regulate our whole body. In addition, our ability to sleep is also related to our circadian rhythm. Sleep and circadian rhythms are one of the most heavily researched topics. Our circadian rhythm not only affects our sleep schedule and cycle, but as well as our ability to eat at certain times during the day and night, and how alert we tend to be.  They can affect our physical, mental, and behaviour throughout our 24-hour cycle. In a study done by Ravi Allada and Brian Y. Chung, drosophila was researched in order to research the output pathways that couple clock cells to overt behaviours. This is similar to a study done by researchers at the University of Colorado Boulder about caffeine and the body’s internal clock.

In Allada’s and Chung’s study, Circadian Organization of Behavior and Physiology in Drosophila, an experiment is conducted in order to research the output pathways that couple clock cells to overt behaviours. This was done through searching for circadian relevant neurons in the brain and creating an output pathway for rest:activity rhythms. For all of the tests, however, it was shown that all sorts of cell ablation and cell stimulation never altered the functions of the clock cells in the Drosophila. In order to examine this, various PI cells were studied and were connected to a clock through a circuit that connected the pacemaker cells to the PI neurons. Also, a corticotropin releasing factor was studied as well. It was found that a neuropeptide called PDF affected the certain types of behavioural rhythms in the flies and a loss of molecular rhythms in the clock cells. Also, a large subset of the pacemaker that was studied indicate that when stimulated, it promoted arousal. In addition, they also studied individual clock cells and sometimes suppressed them. By suppressing different clock cells and clock functions in different areas, the researchers were able to see the responses to light, mating, sleep, and learning and memory. By looking at all the systems and how they connected to the circadian rhythms, they were able to conclude that these rhythms throughout the body (light, mating, sleep, learning, memory, feeding, etc) were directly correlated with the clock cells in the flies.

With circadian rhythms in humans, however, we tend to respond to light and darkness in order to control our biological clock. Our biological clock controls our circadian rhythms through groupings of molecules in cells that interact together all throughout the body. The suprachiasmatic nucleus in our brain is our master clock. In a study done at University of Colorado Boulder, it was shown that caffeine disrupts the body’s internal clock. Five volunteers were randomly assigned to consume as much caffeine in a double espresso three hours before their bedtime, were exposed to bright lights, or given a placebo. Throughout 49 days, they were studied and their melatonin levels were also studied as well. Those volunteers who took caffeine in low-light conditions ended up experiencing a 40-minute phase delay of the circadian rhythm. Those were who were exposed to bright lights had their circadian clocks go back by 85 minutes. Those who were under both conditions, caffeine and bright lights, had their circadian rhythm disrupted by 105 minutes. With the circadian rhythm being shifted later, it was concluded that the caffeine also affected the physiology of humans because when the circadian rhythm is shifted back, it can affect behaviour and physical processes throughout the day. It usually results in slower behavioural processes and physical movement. Therefore, the presence of caffeine changed their circadian rhythm.

When looking at the study of the Drosophila and the study with the caffeine, it can be concluded that the circadian rhythm can drastically change with humans, but that the circadian rhythm is a lot more complicated with Drosophila. With the flies, the clock cells controlled many different other rhythms throughout the flies: eating, mating, sleep, courtship, etc. However, with humans, it was shown that one drug could affect the whole circadian rhythm and completely disrupt it. However, both studies show the importance of the circadian rhythm and the effect of it throughout the entire body. For flies, the circadian rhythm is connected to all other systems throughout the fly. For humans, the circadian rhythms are still connected to our mental, physical, and behavioural processes. Therefore, any disruption to our circadian rhythm can heavily affect our regular body system. These two research studies directly tell us that our circadian rhythm should not be faltered with and the importance of our circadian rhythm overall. 

Allada, R., & Chung, B. (2010). Circadian Organization of Behavior and

Physiology of Drosophila. The Annual Review of Physiology.

doi:10.1146/annurev-physiol-021909-135815

Coffee at night disrupts body's internal clock: Study - The Economic Times. (2015, September 17). Retrieved October 16, 2015, from http://economictimes.indiatimes.com/magazines/panache/coffee-at-night-disrupts-bodys-internal-clock-study/articleshow/48995541.cms