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Biological Aspects of Time

Time affects humans in a variety of ways. We notice time as it slips by us when we’re spending a day with friends or trying to take a test in a short class period. Athletes from around the world notice time when they’re competing in the Olympics. Some cultures do not measure time any more specifically than months and days, while others live their lives in sync with the rising and setting of the sun. Other cultures live by the clock, and even the seconds that pass by can cause anxiety. So, we notice the effects that time has on the way we go about our daily lives, but do we, as living creatures, notice how time affects us biologically? Even if we don’t always notice it consciously, our bodies do.

Your body has probably experienced the biological effects of time on multiple occasions. Have you ever experienced jet lag flying across an ocean or even just across a couple time zones? Have you ever experienced the "winter blues" or switched to the night-shift at work and had trouble readjusting to your new schedule? Did you feel tired when you knew you should be awake? Have you ever felt much colder than usual when you were excessively tired? Chances are that you have experienced one or more of these things before. Time actually has a significant effect on the way our bodies function. Come along and explore the many fascinating biological impacts of time.

Biological aspect - human clock - The Inner “Tick-Tock”

An interesting biological aspect which applies to the existence of all living things is the biological clock, even though the biological clock is not actually a physical part of an organism’s biology. For example: we all know that we would never find a clock built into our human anatomy—ticking away and keeping time inside of us even setting its own alarms! However, humans and other animals feel the effects of the biological clock every day. “An internal biological clock is fundamental to all living organisms, influencing hormones that play a role in sleep and wakefulness, metabolic rate, and body temperature” (“How Biological Clocks Work”). So, although humans may not always realize that they have biological clocks, they feel the effects of this essential biological mechanism every day.

The source of our biological clock is in our cell and neurological structures. This is another way of saying that our biological clock is partially controlled by our brains. In reality however, out biological clock runs on autopilot, with complete independence; we have no control over how it works. “The clock is a self-governing mechanism that is entrained to the day–night cycle by the hormone melatonin, released by the pineal gland in the brain during darkness” (“Animal Behavior”).

The twenty four hour cycle that our bodies work on is known as a circadian rhythm. “Circadian” is a Latin word which means, ‘about a day’. (“How Biological Clocks Work”). On Earth, our biological clock runs on a twenty-four hour cycle because a significant piece of it is triggered by simple daylight. Light from the sun passes through our eyes and is detected by nerves in the retina, which is a sensitive area at the back of the eye. These nerves pass a signal along to the brain. “Some of these nerves feed the hypothalamus, which is a part of the brain that regulates body temperature, water, sugar ratios, and also fluid secretions. It houses the suprachiasmatic nucleus, which is a bundle of nerves that controls the body’s circadian rhythms” (“Jet Lag”). This also explains why circadian rhythms affect body temperature. The temperature of our bodies rises during the day, drops in the middle of the night, and begins to rise again in the early morning (“Jet Lag”).

From an evolutionary point of view in the animal kingdom, we presume biological clocks were developed in part so that animals could be best prepared for various situations and opportunities, like an early bird taking off at dawn to get the worm (“Animal Behavior”). We do know for a fact that animals mate and migrate to a very definitive internal clock and timetable.

Although we, as humans, live on a twenty-four hour cycle, we must sometimes adjust to extreme situations and reset our biological clocks temporarily. Readjusting our biological clock can sometimes lead to problems. A change in jobs or lifestyle can often lead to drastic changes in our daily schedules which in turn affects our internal clocks and makes us moody or depressed. Adults who work the third shift—meaning that they are required to stay up through late hours of the night and early morning—are living backwards in terms of their circadian rhythm. The circadian rhythm would be saying that when it’s getting dark outside, it’s time to sleep and when it is becoming light outside, it’s time to wake up, which is totally opposite to the way you would be living.

The effects of serious illnesses can also be magnified in people who have readjusted their biological clocks. Sleep patterns can also be seriously disturbed (“How Biological Clocks Work”). One of the most common effects of a readjusting circadian rhythm is jet lag, which will be discussed further in another article. People should be mindful of the fact that they have a sensitive biological clock, and that its natural cycle should be disturbed as infrequently as possible.

Biorhythms: The Facts and the Doubts

Biorhythms were discovered, or created, by Dr. Wilhelm Fliess about one-hundred years ago (“What Are Biorhythms?”). Dr. Fliess was a nose and throat surgeon in Berlin (Coveney and Highfield 313). He noticed behavior patterns in his patients over time and began to carefully monitor these patterns—looking for relationships between them and the states of physical, mental, and emotional well-being in his patients. He found the physical cycle to be twenty-three days long, the emotional curve to be twenty-eight days long, and the mental curve to be thirty-three days long (“What Are Biorhythms?”). Eventually it became possible to graph these curves and allow people to see when their emotional, physical, or mental well-being would be at its highest or lowest. A typical biorhythm chart shows three lines, which are sections of a curve. These lines represent the three categories of human health mentioned above. Sections above the midpoint line indicate high times or good times for the biorhythm, sections below it indicate low or bad times. There is also a midpoint line which shows critical times in the biorhythm (“What Are Biorhythms?”). A critical day signifies either the worst day or the best day of the cycle.

The science upon which biorhythms are founded is often questioned, and biorhythms are easily confused with biological rhythms (circadian rhythms). “Biological rhythms should not be confused with biorhythms, which are purported physical, intellectual and emotional cycles said to be determined by the date and time of a person’s birth. Most scientists regard the study of biorhythms as a pseudoscience” (Dotto 42). Many people use them every day to warn themselves against certain activities and encourage themselves toward others. Skeptics say that the charts are unreliable and cannot be used to support our lifestyle choices. Still, the Encyclopedia of Occultism and Parapsychology gives some convincing facts to back up the validity of biorhythms, such as: the suicides of Marilyn Monroe and Judy Garland on their critical days, as well as Billie Jean King defeating Bobby Riggs at tennis during a high point in her cycle (“Biorhythm.”). Is it a coincidence? What do you think? Below, you have the option of checking your own biorhythms. You can be the one to decide if biorhythms can be trusted. Are you having a good day, but your biorhythm chart says you should be having an awful one? Find out.

Click on the link below to see a typical graph of your biorhythms:

Biological aspect - human clock - Lagging Behind: The Effects of Jet Lag

"I think a major element of jetlag is psychological. Nobody ever tells me what time it is at home."
David Attenborough

Imagine that you are going on a trip to a faraway place. Pick a place that is at least a few time zones away. It could be anywhere. You are taking a plane, and you are packed and ready to go. You get on the plane and settle down for a long trip. How do you suppose you will feel once you reach your new destination? If you left in the morning, chances are you might find yourself in the middle of the night when you arrive if you flew east or you might find yourself arriving at just about the same time of day that you left if you flew west. For the first few days of your trip, you may find it difficult to adjust to when it gets dark outside as well as to when it gets light. Why does this happen? The trouble that plane-travelers have when trying to adjust to a normal day in a distant land is called desynchronosis (“Jet Lag”). It is more commonly referred to as jet lag.

What jet lag entails is a type of alteration of a person’s 24-hour circadian rhythm. It is probably one of the most extreme ways in which our biological clocks are forced to adjust. Less severe forms of desynchronosis happen to people who switch between day shift and night shift work. Jet lag is caused when our internal biological clock becomes desynchronized with our external environment as a result of traveling through multiple time zones in a short period of time (“Jet Lag”). The symptoms' severity are affected by the number of times zones you cross. The greater the number of time zones you cross, the more severe the symptoms will be. As mentioned above, jet lag can be problematic for travelers trying to adjust to a schedule in a distant place. The triggers provided by the rising and setting of the sun—as discussed in the article on biological clocks— run havoc with our biological clocks because the sun's time, here and now, is different from our biological clock's time, here and now. So, we feel stuck in our old circadian rhythm as our body tries to adjust to the new one.

Common symptoms of jet lag are disorientation, fatigue, inability to sleep, headaches, and onsets of lethargy or restlessness. Someone suffering from jet lag may feel like they want to get a good night’s rest and sleep for nine hours when it is only mid-day. This can happen when they leave on their journey in the late afternoon and arrive at their destination ready to fall asleep, but due to the changes in time zones it is only mid-day in their new destination.

Trainers for athletic teams that compete across time zones are well aware of the problems with being a non-host team. To help their players adjust and minimize the effects of jet lag, they change the times their team members go to bed before the trip and try to arrive at the host site a few days ahead of the competition. Once on the plane, they also have their players set their watches to the host country's local time so that they mentally tune in to the new local time as quickly as possible and begin to adjust their behavior accordingly. It usually takes a week for someone to completely rid themselves of feelings associated with jet lag (“Jet Lag”).

Think Fast: A Look at Reflexes

"Rational behavior requires theory. Reactive behavior requires only reflex action."
W. Edwards Deming

Have you ever been to a doctor’s appointment and had your reflexes checked? The doctor takes out an instrument with a hard, triangular rubber knob on the end, and taps it right below your kneecap. Do you know what should happen as a result? Your reflexes should react to this tap by causing your leg to jump upwards slightly from its downward hanging position. This is known as the patellar reflex. “It is also known as a deep tendon reflex (DTR) because the doctor is actually tapping on a tendon called the patellar tendon. This tap stretches the tendon and the muscle in the thigh that connects to it. A message then gets sent to the spinal cord that the muscle has been stretched." (“What Are Reflexes?”). This message eventually gets to the brain as well, but reflexes and spinal cord messages often have to travel faster than the messages to the brain. That is why reflexes are defined as instantaneous or “involuntary” reactions.

Reflexes also come into play in the world of sports. Athletes often are prided for having quick reflexes, which ultimately translates into fast reaction time. Reaction time is the time that passes between the introduction of a stimulus and when the reflex kicks in. For example, when a runner hears a gunshot fired to signify the start of the race, his reflexes must kick in so he can react to the gunshot, move his legs, and start running. A swimmer deals with the same situation when they are waiting for the start signal. As the swimmer crouches over the block, prepared to dive in, the signal sounds. The swimmer’s reflexes determine his reaction time. That is, his reflexes determine how much time passes between the actual sounding of the signal and the point in time when the swimmer explodes off of the block and splashes into the pool. Reflexes and human reaction times are directly related.

A dictionary defines reflexes as “…an involuntary action or response, as a sneeze, blink, or hiccup…” and “…an unlearned or instinctive response to a stimulus…” (Webster’s II). The main reason that humans have reflexes is to provide protection. Reflexes protect us from things that are potentially dangerous, before these things have a chance to harm us (“What Are Reflexes?”). So many of the biological processes we experience every day employ reflexes: blinking, pupil enlargement and reduction, and jumping or twitching. We blink to keep dangerous materials in the air out of our eyes. Our pupils enlarge or get smaller to control the amount of light reaching our highly sensitive eyes (“Reflexes”). The patellar reflex is an example of a jumping or twitching reflex often used in sports to avoid injury or get a jump start out of a gate or off a block in a sporting event. What would have helped a cave man escape from a marauding, fanged predator? Reflexes! As soon as he heard the predator rustling about in the bushes, the cave man’s reflexes would kick in, forcing the muscles in his legs to react in a split second, and allowing him to escape and run away.

Just how fast are human reflexes and reaction times? Most times they only amount to fractions of a second. It is difficult to be more precise however because reflex time varies from person to person. How fast a person’s reflex or reaction time is also depends on how often that person’s brain is made to react. In other words, reflexes can be trained because the more practice your reflexes get, the faster they become (Kelly). When driving a vehicle, humans typically should have a reaction time of about 0.75 to 1.5 seconds on average to ensure safe driving (“Rule 4: Don’t Speed!”). Still, factors such as age, disability, and as we have seen, practice can alter reaction times.