A: When sensory receptions are exposed to a continuous and unimportant stimulus, they often adjust so that the sensation become less acute. Q4: List the structures that protect the eye (1 point). A: The skull bones form the walls of the eye orbit Upper and lower eyelids aid in protecting the eye’s anterior portion Eyelashes and eyebrow help keep foreign matter out of the eye Tears lubricate the eye and contain an enzyme that protects against infection Q5: Describe location and function of the following structures of the eye: sclera, iris, rods and cones, conjunctiva, cornea, retina, optic disc, macula lutea, optic nerve, pupil, lens (3 points).
A: sclera: In the fibrous tunic, made of tough connective tissue and is referred to as the white of the eye. iris: The pigmented ring that gives an eye its distinctive color. It is composed of two sets of muscle fibers that govern the size of the iris’s central opening the pupil. rods: Highly sensitive to light and thus function best in dim light but they do not provide a sharp image or differentiate colors they are more numerous than the cones and are distributed more toward the periphery of the retina. Cones: Function best in bright light are sensitive to color and give sharp images the cones are localized at the retinal center especially in a tiny depressed area near the optic nerve that is called the fovea centralis. conjunctiva: Inflammation of the conjunctiva, cornea: The anterior portion of the fibrous tunic is the forward-curving transparent and color- less cornea. retina: Complex structure with multiple layers of cells the deepest layer is augmented layer just superficial to the chloride. optic disc: The blind spot on the retina where no image can form. macula lutea: The yellowish spot in the fovea. optic nerve: each of the second pair of cranial nerves, transmitting impulses to the brain from the retina at the back of the eye. pupil: a hole located in the centre of the iris of the eyethat allows light to strike the retina. lens: a transparent, biconvex structure in the eye that, along with the cornea, helps to refract light to be focused on the retina. Q6: Identify the three tunics of the eye (1 point). A: Fibrous tunic Vasular tunic Nervous tunic Q7: Define refraction and list the refractive parts of the eye (2 points). A: Refraction: the bending of light rays as they pass for one substance to another substance of different densities. Parts: Transparent cornea, aqueous humor, lens, nitrous body Q8: Differentiate between the rods and cones of the eye (1 point). A: Rods: Highly sensitive to light and thus function best in dim light but they do not provide a sharp image or differentiate colors they are more numerous than the cones and are distributed more toward the periphery of the retina.
- Spring '18
- Mark Bolke