Monday, December 17, 2012

Form Fits Function

In the current series of posts on human sight, this title may seem irrelevant at first glance. An explanation is in order. Perhaps you have been asked whether you would select the sense of sight or hearing should you be forced to do without one or the other. The question is irrelevant to our experience, but may trigger personal speculation and introspection on how highly valued and treasured all our sensory gifts are. Among the five major senses of the human body, sight probably ranks as the sense we would least like to do without. With this introduction, we look more closely at the elements of form and function related to vision.

There is an important physiological basis for judging that sight may be the paramount body sense, even though we may dislike prioritizing in this manner. According to estimates, 70% of the sensory neurons in our body are located in the retina. The retinal tissue is just over 1000 square mm in area. Roughly, this converts to the area of a teaspoon. In this small area there are well over 100 million rod cells and four million cone cells. This gives 150,000 cones per square millimeter in the central retina, the area providing clear, color vision of our central visual field. Cone cells function for humans in bright light. In the periphery of the human retina, there are many more rod cells which provide us with effective colorless vision even in extremely dark conditions.

Form fits Function is a principle of life science articulated in most modern biology textbooks. It is applicable throughout the living world. The principle applies to molecules, cells, issues, organs, and complete organisms. Among biology books, this principle could appropriately appear in every chapter covering the relationship between biological entities and their purpose. The principle applies to the hundreds of tasks accomplished within an individual organism, to the relationship of that organism to other organisms, and to the relationship of an organism to its environment.

In our current discussion of the phenomenon of sight, there is appropriate application of Form fits Function to the mechanism of the sensory detection of light by the human retina. The light reaching our eyes from nearby or distant objects arrives as billions of photons streaming from billions of data points from the light-giving object. We might say that each atom of those light-giving objects, complete with its vibrating electrons, is the source of a light data point. From each data point flows photons of electromagnetic light energy. Therefore, we have the form of plentiful light generation and effective transmission of light energy through space. What remains is the function of light detection, that is, our sensory organs of light detection. Initially, light is transmitted through the layers and substances of our eye—the cornea, aqueous humor, lens, and vitreous humor. However, the most spectacular functional organ, or, if you will, body tissue, is the specialized retina with its millions of rods, cones, and other specialized cells. These cells are triggered by photons to begin their work of sensing messages of light to the brain.

The form of light, billions of electromagnetic waves called photons, fits the function of the billions of retinal cells with their ability to detect billions of light data points. Beyond the retina, data will be sent to the brain as billions of simple electrical “all or none” pulses of voltage. The most fascinating aspect of “seeing” has yet to be discussed in an upcoming post.

Who is the author of the principle of “Form fits Function?” This blog has consistently proposed that our cosmos is a creation of the God of the universe, the Creator of all things, the God of Judeo-Christian scripture. He has designed all things after His will. We interpret scientific information in this light.