Cow Eye Dissection Pre-lab Key

Cow Eye Dissection Pre-Lab Key Before conducting the cow-eye dissection complete all pre-lab questions and label all questions: Background Information: 1. The retina is covered with millions of light sensitive cells called rods and cones. When these cells detect light, they send signals to the brain. Cone cells help detect colors. Most people have three kinds of cone cells, S, M, L cones. Each cone will receive a specific wavelength of light. S-Cones (short wavelength) absorb blue light. M-cones (medium wavelengths) absorb green light and L-cones (Long wavelength) absorb red light. When we absorb these wavelengths the neuron sends an electrochemical impulse to our brain and we process the information so we can see. 2. Scientists have come up with scenarios through which the first eye-like structure, a light-sensitive pigmented spot on the skin, could have gone through changes and complexities to form the human eye, with its many parts and astounding abilities. Through natural selection, different types of eyes have emerged in evolutionary history—and the human eye is not even the best one, from some standpoints. Because blood vessels run across the surface of the retina instead of beneath it, it is easy for the vessels to proliferate or leak and impair vision. 3. Rod cells are highly sensitive to light and operate under dim lighting conditions. Cone cells function under ambient and bright lighting conditions, exhibit rapid responses to variations in light intensity, and are responsible for color vision and high visual acuity. 4. Describe in your own words what this graph represents. Each Cone cell absorbs a specific amount of light. For instance S-cones absorb blue light at a peak value of 420nm. Green cone’s peak absorbance is 534nm whereas red cones absorb 564nm. These three cones along with rod cells allow us to see a continuous spectrum of visible light. Lab Procedure 5. Create a numbered list of the procedure you will follow during the lab. ANSWERS VERY How does the human eye move? extrinsic muscle expansion and contraction. What’s the function of the cornea? tough covering over the iris that helps protect the eye and directs the light towards the lens. What’s the function of the iris? controls how much light enters the eye. What are some safety concerns you must take into consideration? Protect your eyes and always cut away from yourself with a scalpel. Clean up and wipe down all lab dissection equipment. 1. Use the structures listed in question #2 and label the diagram. 2. Describe the function of the following structures: Cornea - tough covering over the iris that helps protect the eye and directs the light towards the lens. Optic nerve- The bundle of nerve fibers that carries the impulse to the brain. Iris - controls how much light enters the eye. Pupil - the opening in the iris that allow light to reach the lens. Retina - a tissue containing light sensitive neurons. Aqueous humor-clear fluid that helps cornea keep its rounded shape Vitreous humor-a thick, viscous fluid which helps hold the delicate retina against the choroid. Ciliary body - a muscle that helps change the shape of the lens. Suspensory ligament - connects the ciliary muscle to the lens. Sclera - A tough white outermost covering of the eye. Choroid layer- mid layer of the eye and contains dark pigments that helps nourish the retina. Tapetum - mid layer of the eye and contains reflective pigments that helps the eye see better at night. Lens - clear, flexible structure that focuses the light on the retina. Blind spot-place where optic nerve leaves the retina Fovea Centralis- the point in the back of the eye with the greatest density of cone cells. 3. Use the pictures below to name the parts of the eye that you will observe in the lab. 1. Retina 2. Scelera 3. Optic Nerve 4. Blind Spot 5. Choroid Layer 6. Tapetum 7. Cilliary Body 8. Iris 9. Pupil 10. Cornea 11. Sclera 12. Vitreous Humor 13. Lens