The sensory system involves hearing, touching, tasting, smelling, and seeing, which provide data for perception. The eye is a sensory organ held by an orbit that allows vision (a detection of light in a way that provides mental images of objects) and holds photoreceptors. Photoreceptors are used to absorb light energy, which are bent by a transparent unit called the lens. Some photoreceptors in the eye are the rod cell and cone cell. Rod cells are used in dim light for coarse images and motion and are concentrated at the edge of the retina, while cone cells are used in daytime for sharp vision and color and are centered at the center of the retina in the fovea. Inside the retina is an optic nerve that lacks photoreceptors, creating a blind spot. The retina is also one of the eye’s internal chambers, along with the ciliary body, which produces vitreous humor. The eye is made of a three-layered structure. The first layer, the cornea, is made of crystalline, a water-solute structural protein. The other layers contain the iris, which determines how much light enters the eye by adjusting the size of the pupil (the opening at the center of the iris). Although eyelids, eyelashes, tears, and conjunctiva protect the eye’s surface, they cannot protect the eye from internal problems such as hyperopia (farsightedness), myopia (nearsightedness), astigmatism, and presbyopia.
The ear enables people to hear or detect sounds. There are different parts of the ear: the outer ear, middle ear, and inner ear. The outer ear holds the pinna that gathers sound waves and sends them into the auditory canal. The auditory canal is connected to the middle ear where air waves are increased and sent to the inner ear. There, the cochlea transfers sound waves into action potentials, which causes its fluid-filled ducts to vibrate. The middle duct of the cochlea has hair cells that bend when pressure waves force the membrane to move. Hearing loss can be caused by loud or repetitive...
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