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EXERCISE 26 Eye and Vision REVIEW ANSWERS 1. Eye shine in nocturnal mammals is different from the “red eye” seen in some flash photographs. Eye shine is the reflection from the tapetum lucidum. What might produce “red eye?” Ans: The condition called “red eye” is due to bright light reflecting off of the back of the retina. 2. Fill in the following illustration using the terms provided. Ans: a. sclera b. choroid c. retina d. optic nerve e. ciliary body f. suspensory ligaments g. cornea h. pupil i. lens j. anterior cavity (anterior chamber) 3. Since the lens is made of protein, what effect might the preserving fluid used in lab have on the structure of the lens? How would this affect the clarity? Ans: In preserved specimens the normally clear lens is denatured and becomes opaque due to the preserving fluid. The protein molecules unwind as they denature and this leads to refraction of the light. 4. What is the consensual reflex of the pupil? Ans: The consensual reflex is the decreased diameter of one pupil when the other pupil is exposed to an increase in light. 5. How does the vitreous body differ from the aqueous humor in location and viscosity? Ans: Vitreous humor is located in the posterior cavity and is more viscous (thicker) than aqueous humor. Aqueous humor is located in the anterior cavity and is more watery. 6. What layer of the eye converts visible light into nerve impulses? Ans: The retina is the region of the eye that converts visible light into nerve impulses.
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7. What nerve is composed of axons of the ganglion cells and transmits action potentials to the thalamus of the brain? Ans: The optic nerve carries the action potentials to the thalamus of the brain. 8. What is another name for the sclera? Ans: The other name for the sclera is the white of the eye. 9. How would you define an extrinsic muscle of the eye? Ans: An extrinsic muscle of the eye is one that attaches to the sclera and moves the eyeball. 10. What gland produces tears? Ans: The lacrimal gland produces tears. 11. What is the name of the transparent layer of the eye in front of the anterior chamber? Ans: The transparent layer of the eye in front of the anterior chamber is the cornea. 12. The iris of the eye has two main types of muscles. Name these two muscles and how they affect the pupil. Ans: The function of the iris is to control the size of the pupil. When the radial muscles contract the pupil dilates. When the circular muscles contract the pupil constricts. 13. Where is vitreous body found? Ans: Vitreous body is found in the posterior cavity. 14. What is the function of the choroid? Ans: The function of the choroid is to absorb light preventing light scattering in the back of the eye providing a brighter image. . 15. Is the lens anterior or posterior to the iris?
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