The human body is composed of 28 to 36 trillion cells. Estimates of how many types of cells exist in our body is over 200. In addition there are many cell sub-types. Some body cells sense conditions within the human body. These are sensory cells, sometimes called sensory neurons. These cells are known as interoceptors, sensing conditions inside the body. Other body cells are exteroceptors, sensing conditions outside the body.
Human senses often detect conditions beyond our body. For instance, the sense of smell (olfaction) originates in the kitchen during meal preparation. The sense of smell is an internal body reaction based on an external stimulus. The sense of taste connects with other senses such as odor. Taste and odor are pleasant sensations created by God for our enjoyment (I Tim 6:17b). The sense of smell could also be a warning that something is burning!
There are many other body senses apart from the familiar five—sight, sound, smell, taste, and touch. Our body’s other sensory systems enable us to maintain balance, feel temperature changes, experience pain, and be aware of the position of our body parts without actually having to see the positions of our legs or arms. Of many examples we could cite, we discuss only one — our sense of balance. Part of our anatomy is a body organ in our inner ear located near our brain. This organ is part of our vestibular system and is composed of semicircular canals filled with fluid. The fluid moves through the canals when we move. This inner ear fluid connects to specialized cells sensitive to body movements and sends electrical impulses to the brain through neural pathways. In turn, the brain directs our muscles to move so our body maintains its balance. Young toddlers are born with a sense of balance evident when they are learning to walk.
Knowledge of the human sense of hearing and sight is even more complex than the sense of balance. Our Creator has gifted us with many senses beyond the familiar top five. Different sources have identified 30 or more human senses. Some of the most interesting sensory cells in the human body are known as exteroceptors. The human body is capable of sensing sound and light. Our sense of hearing is effective during conversations with friends in the same room, at a musical concert, or during a thunderstorm. Human vision extends our sensory perception to objects in outer space.
Early science lessons from my father involved sound; summer thunderstorms provided the subject matter for those family lessons. Sound travels approximately 1100 ft/s. Therefore, if we observe a distant lightning flash, we could calculate the distance to the storm by counting the time from seeing the lightning to hearing the thunder. In five seconds sound travels about one mile, in ten seconds about two miles.
The speed of light is the ultimate speed in our universe. Light travels at a finite speed: 186,262 miles/sec. Light travels from our earth to the moon in just over one second. It could travel around the earth at the equator about 7.5 times per second. At that speed light would take eight minutes to reach Earth from the Sun. Light from the nearest star would take over four years to reach Earth. We express the distance to the nearest star as four light years rather than an incomprehensiblylzrge number of miles.
Compared with light, sound is a slowpoke. Light travels almost one million times faster than sound but the physical dynamics of the phenomena are different. Sound cannot travel without a medium such as gas, liquid, or solid but light can travel through empty space. Light and sound are perceived by humanity with their sensory system which our Creator has generously supplied when He created our physical bodies. The human sensory system is a marvelous gift from the Creator. Sensory systems are a divine gift not only for humanity, but also for all living things.
Psalm 139:14 (NIV) “I praise you because I am fearfully and wonderfully made; I know that full well, your works are wonderful.”
