Living things, both plants and animals, have a biological clock that is extremely important for survival. The human master clock is located in the hypothalamus of the brain in a tiny region called the suprachiasmatic nucleus (SCN). The SCN controls what is known as the circadian rhythm, a 24-hour rhythm of the body.
The SCN interacts with many regions of the brain to control sleep, hormone levels, alertness, body temperature, digestive activity, immune functions, and other systems. It coordinates the various rhythms of the body to keep us going through the day. This biological clock works in many ways that we don’t even realize.
Specialized cells in the retina of the eye connect directly to the SCN. When the eye senses light, the SCN receives the message and starts body process going by telling the various systems what to do and when. When you wake up in the morning, the clock signals enzymes to start flowing for your first meal. Hormones raise body temperature and blood pressure so that you can face the day.
During the day, the biological clock starts various chemicals and hormones so they will be available and functioning when they’re needed. Therapeutic medicines work best when taken at certain optimum times according to the biological clock. At night the circadian rhythm in the SCN sends a message to the pineal gland to produce the hormone melatonin making us sleepy.
This is a highly-simplified summary of an amazingly complicated system. Complex systems like this don’t happen by chance indicating that this is another evidence of design. Day and night, months and seasons regulate the systems of humans and all other creatures. Genesis 1:11 tells us that God made the Sun and Moon to “mark seasons and days and years.” Those simple words contain profound truths that we have only begun to understand.
–Roland Earnst © 2018