Anatomy and Function of Vision Term Paper

Pages: 5 (1729 words)  ·  Bibliography Sources: ≈ 4  ·  File: .docx  ·  Level: College Senior  ·  Topic: Physics

Anatomy and Function of Vision

This report is about the human sensory system and perception function of seeing or vision. The report delves into the physical anatomy of the specific areas involved for a person to see and therefore appreciate his or her immediate external environment. We humans often take vision for granted but it is truly a crucial aspect of our evolutionary success. Therefore, the objective of this work is to offer some existing detailed insights into the process in order to provide a better understanding of how vision significantly contributes to life. It is very important for the average person to appreciate the dominant role vision has come to play in directing and monitoring a plethora of decision making skills and reflexes from the fight or flight response to the choosing of our life partners or mates.

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The report attempts to offer an understanding of how this gift works from a basic scientific perspective and clarifies that a comprehensive definition of vision must go well beyond the classic 20/20 sight definition scale employed by the majority of our culture. The 20/20 approach does distinguish a scale to measure the ability to see but it only offers a limited concept of the overall process. "If you have 20/40 vision, it means that when you stand 20 feet away from the chart you can only see what a normal human can see when standing 40 feet from the chart. That is, if there is a "normal" person standing 40 feet away from the chart, and you are standing only 20 feet away from the chart, you and the normal person can see the same detail. 20/100 means that when you stand 20 feet from the chart you can only see what a normal person standing 100 feet away can see. 20/200 is the cutoff for legal blindness in the United States." (Bainco, 2005) This report aims to show that vision should be defined as a far more dynamic phenomenon and is more a learned process of deriving and interpreting meanings and thus altering our very thinking and decision making processes.

Term Paper on Anatomy and Function of Vision Assignment

To fully comprehend the intricacies of vision, the report delves into the anatomy of the eye, the associations to our brains and the brain activity as well as the concepts of directing action from light energy. Again, to fully grasp that humans have adapted and evolved by creating physical and visual skill sets of interpreting light to provide intelligent information for our brains is an amazing outcome in the scope of nature's evolutionary process.

Light and the Sun

Our planet is as it is because of the main function of the sun. The sun is the center and most likely the most critical part of our solar system because of the light it offers to feed our planet and drive all life. There is little doubt from a scientific perspective that our planet would be greatly altered without the sun and most likely would have no life. For living creatures to evolve, expand and thrive, they have had to learn to function on the ideas or concepts of sensing light in some way.

This notion applies to all living creature on our planet and therefore could be considered to be an almost universal law. Consider that all plants utilize light through the concept of photosynthesis to feed themselves and mammals and other life forms utilize light to hunt, mate and preserve themselves through the cycles of light that are present. And it is not just during periods of daylight because even at night, there is enough light to sustain life and alter the flow of plant and animal cycles. Light also affects us.

Human evolution is what it is for a few major developments such as the improvement of human stereoscopic vision for appreciating light, levels of color and levels light absence, the development of our large brains, our thumbs and our ability to utilize free hand locomotion. All of these phenomenons have helped us evolve. However, if we had not had the ability to appreciate light in the way that we did and still do, there is little doubt that we would have more than likely become extinct. That is why the inner workings of our eyes and the idea of vision are so important to us.

Human Eye Anatomy

The human eye is more or less a fully functioning self-contained camera with a never ending supply of power. "Other elements of the eye anatomy support the main activity of sight: Some carry fluids (such as tears and blood) to lubricate or nourish the eye. Others are muscles that allow the eye to move. Some protect the eye from injury (such as the lids and the epithelium of the cornea). And some are messengers, sending sensory information to the brain (such as the pain-sensing nerves in the cornea and the optic nerve behind the retina)." (Segre, 2005) (Segre, 2005)

The function of the eye works mainly be allowing light to come in and pass through the cornea that acts in the same manner as a camera's aperture. Because light is available in a variable sense or scale, the human body has learned to allow levels of light to enter through it's pupil which acts like a camera shutter. In other words, it opens and closes as needed based on the available levels of light. In order to accept the levels of light and also to allow us to focus in or out on specific things, the eye uses the retina to gather the detail and pass the information on to our brains. "The eye has been called the most complex organ in our body. it's amazing that something so small can have so many working parts. But when you consider how difficult the task of providing vision really is, perhaps it's no wonder after all." (Segre, 2005)

Vision Function

An overview of the basic anatomy and physiology of how the eye responds to light to begin the visual process establishes the foundation of vision. The amount and intensity of light entering the eye helps to dictate which neurological information will be forwarded through the optic nerve to the brain for our processing and interpretation. In general, vision can be divided into three distinct levels of light intensity which are daylight (photopic), twilight (mesopic) and low light, night (scotopic) function.

Photopic vision is what we would consider to be bright light levels or daylight interpretation. "Each cone cell has one of these pigments so that it is sensitive to that color. The human eye can sense almost any gradation of color when red, green and blue are mixed." (Bainco, 2005) (Bainco, 2005)

For this function, neuroreceptors called cones dominate our eye's response to whatever levels of light are available. In the process, our inner photosensitive retina uses an estimated 7 million cones that are concentrated in the retina and correspond to our ability to use straight ahead vision interpretations.

An anatomical area within the retina called the macula and a depression called the fovea in the macula consists almost entirely of cones. These cones convert light energy into neural energy which is sent to the brain via the optic nerve. Any reflected light that is not in our straight line vision also stimulates our retina cones and the brain interprets movement, forms, shapes, textures, colors or contrast points to help us understand our daytime or bright light environment. (Bianco, 2005)

There is a period when light is declining and but darkness has yet to take hold. This period referred to as dusk is technically a period of light transition called mesopia. Humans have evolved to a point where we shift from a cone domination vision process to a rod dominated process during this transitional period. In other words, we use both rods and cones during this mesopic period. It has been estimated that most humans have over one hundred million rods which are located throughout our peripheral retinas.

The function of these rods is to send all visual information to our brains that may be considered to be external movement and organizational responses to lower levels of light in our environments. "The innermost layer is the retina -- the light-sensing portion of the eye. It contains rod cells, which are responsible for vision in low light, and cone cells, which are responsible for color vision and detail. In the back of the eye, in the center of the retina, is the macula. In the center of the macula is an area called the fovea centralis. This area contains only cones and is responsible for seeing fine detail clearly." (Bianco, 2005)

Some concepts about our evolution suggest that we were more than likely hunted by predatory carnivores at this time of day so our bodies created a new defense process to combat the threats. Therefore, during mesopia there is a slow process of reduced color perception and other losses as we depend less on the cones and more on the rods.… [END OF PREVIEW] . . . READ MORE

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