![]() The senses of smell and taste are not as fundamental to human survival as vision and hearing. Stimulation of the smell and taste receptors transmit signals terminating in the temporal lobe of the cerebral cortex. The surfaces ( epithelium) of the nasal passage and tongue contain receptors sensitive to specific odors and tastes. Figures 3.16 and 3.17 show the neural pathways for the senses of taste and smell. Luciano Pavarotti and William Wright, from Pavarotti, My Own Storyįigure 3.15 portrays the different cells for salty (Type I), sweet, umami (flavor of glutamates) and bitter (Type II), and sour (Type III) tastes. One of the very nicest things about life is the way we must regularly stop whatever it is we are doing and devote our attention to eating. ![]() The neural information from the basilar membrane is transmitted to the auditory nerve and then to the brainstem. Human hearing extends approximately from 20 to 20,000 Hz (vibration cycles per second). Starting at the end (apex) of the cochlea, the hair cells are responsive to increasing frequencies of sound waves. The limits of human hearing are determined by the nature of tiny hair cells contained within the basilar membrane lining the cochlea (see Figure 3.14). These vibrations are amplified by the ossicles and transmitted to the cochlea. When sound waves reach the eardrum they cause it to vibrate. The inner ear consists of the cochlea, a snail shaped tube filled with fluid. The middle ear is in an enclosed chamber behind the eardrum and includes the three tiniest bones (ossicles) in the body often described as the hammer, anvil, and stirrup. The outer ear includes the ear flap, ear canal, and eardrum. The ear can be divided into the outer ear, middle ear, and inner ear. Figure 3.13 Anatomy of ear (brown is outer ear, red is middle ear, purple is inner ear). ![]()
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