Sometimes it's other factors, (like genes or biology) that play a role.įlying across the country on the red-eye is a prime example of how we can disrupt our own clocks, and a far more extreme example than the spring forward/fall back ritual in many parts of the U.S. Sometimes we do things ourselves that disrupt our normal rhythms, like flying to a distant time zone. This can happen for different reasons, and we're just starting to understand them in greater detail. Some of the best knowledge we have about the roles the biological clock plays in our health come from instances in which the cycle gets out of sync. And activity of the stress response system - particularly in secretion of the stress hormone, cortisol - is reduced during the nighttime hours, and heightened in the early morning.Īlthough there are certain areas of the body, like the heart, that are able to govern their own function to some degree, there is strong evidence that the body clock plays a major role in controlling many of these fluctuations (such as in blood sugar) over the 24-hour period.ĮNVIRONMENTAL DISRUPTIONS TO THE BODY'S CLOCK This is likely because the body is better at fighting infection while it is at rest, and energy can be poured into the effort, rather than into other functions. Compounds that encourage the inflammatory response rise at night, (which is why fevers tend to spike then), and those that inhibit it rise during the day. The chemicals involved in immune system function also vary. For example, the hormones responsible for hunger and metabolism rise and fall over the course of the day. Other systems also follow a daily rhythm, many of which are controlled by hormones and other compounds that receive cues from the biological clock. When the sun rises, melatonin secretion is inhibited, and the brain's awake circuits resume. When it's dark, more melatonin is secreted, which signals the brain to go into sleep mode. When night falls and there is less light input to the SCN, the production of melatonin, the hormone responsible for making us feel sleepy, goes up. Melatonin is one hormone responsible for our body's daily cycle. Our Behaviors and Body Functions Run on Cycle The need for both kinds of cues - light and genes - make the biological clock a classic example of how genes and the environment work in tandem to keep the system functioning well. And when people or animals lack the genes that help control the clock's cycle, their sleep-wake cycles can stray even further, or be absent completely. When humans are allowed to run off their body's clock apart from input from the sun, by being kept in continuous darkness, the body's daily cycle tends to lengthen to about 25 hours. To stay on the 24-hour cycle, the brain needs the input of sunlight through the eyes to reset itself each day. The system requires both types of input - light and genes - to keep it on track. This location enables the SCN to receive the cues it needs from light in the environment to help it keep time.īut genes also influence the body's clock and circadian rhythms. The idea of a biological clock may sound like a quaint metaphor, but there is actually a very distinct brain region that is charged with keeping time: It is an area called the suprachiasmatic nucleus (or SCN), situated right above the point in the brain where the optic nerve fibers cross. YOUR BODY WANTS TO RUN LIKE A SWISS WATCH In fact, keeping your body's daily cycle on an even keel may be one of the best things you can do for your overall health. We're beginning to understand more about how the clock interacts with and helps govern the function of other systems and affects our overall health.
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