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Cecie Starr Christine Evers Lisa Starr www.cengage.com/biology/starr Chapter 30 Sensory Perception (Sections 30.6 - 30.9) Albia Dugger • Miami Dade College 30.6 Visual Disorders • Vision is impaired when light is not focused properly, when photoreceptors do not respond as they should, or when some aspect of visual processing breaks down • Common vision disorders result from defective or degenerating photoreceptors, misshapen eyes, a clouded lens, or excess aqueous humor Color Blindness • Sometimes one or more types of cones fail to develop or function improperly • Red-green color blindness is an X-linked recessive trait in which a person has trouble distinguishing reds from greens • As in other X-linked traits, it shows up more often in males Lack of Focus • Disorders in which light rays do not converge as they should cause focus problems • Astigmatism results from an unevenly curved cornea, which cannot properly focus incoming light on the lens • Nearsightedness or farsightedness occurs when the distance from the front to the back of the eye is longer or shorter than normal Nearsighted and Farsighted • In nearsightedness, light rays converge in front of the retina; in farsightedness, light rays are focused behind the retina Nearsighted distant object Fig 30.10a, p. 495 Farsighted close object Fig 30.10b, p. 495 Age-Related Disorders • A cataract is a clouding of the lens • In age-related macular degeneration (AMD), photoreceptors in the macula are destroyed, which clouds the center of the visual field more than the periphery • Glaucoma results when too much aqueous humor builds up inside the eyeball Age-Related Disorders • Vision with cataracts • Vision with AMD ABC Video: Restoring Sight 30.7 The Chemical Senses • The senses of taste and smell involve chemoreceptors • taste receptors • Chemoreceptors involved in taste • olfactory receptors • Chemoreceptors involved in sense of smell Sense of Smell • In humans, olfactory receptors line the nasal passages • Olfactory receptors detect water-soluble or volatile (easily vaporized) chemicals • Receptor axons carry signals to olfactory bulbs in the brain • Many animals use olfactory cues to navigate, find food, and communicate, as with pheromones Pheromones • Pheromones are chemical signals that act as social cues among many animals that have the means to detect them • Example: Olfactory receptors on antennae of a male silk moth help him find a pheromone-secreting female • In the nasal cavity of reptiles and most mammals, a cluster of sensory neurons forms a vomeronasal organ that responds to pheromones Key Terms • pheromones • Signaling molecules that affect another member of the same species • vomeronasal organ • Pheromone-detecting organ of vertebrates Olfactory Receptors Olfactory Receptors olfactory tract from receptors to the brain olfactory bulb bony plate ciliated endings of olfactory receptor that project into mucus inside nose Fig 30.12, p. 496 Sense of Taste • Taste receptors help animals locate food and avoid poisons • In humans, taste buds are located in specialized epithelial structures (papillae) on the tongue’s upper surface • Tastes are combinations of five main sensations: • sweet (glucose and the other simple sugars) • sour (acids) • salty (sodium chloride or other salts) • bitter (plant toxins, including alkaloids) • umami (amino acids such as glutamate) Taste Receptors Taste Receptors taste bud hairlike ending of taste receptor section through circular papilla sensory nerve Fig 30.13, p. 496 Key Concepts • Chemical Senses • Binding of specific chemicals activates chemoreceptors in the lining of the nose and mouth • Many animals also have organs that detect pheromones: chemicals that one member of a species uses to communicate with another member of the same species 30.8 Keeping the Body Balanced • The vestibular apparatus, a system of fluid-filled sacs and canals in the inner ear, houses organs essential to maintaining posture and sense of balance • These organs of equilibrium detect gravity, acceleration, and other forces that related to the body’s position and motion • They include hair cells, mechanoreceptors with specialized pressure sensitive cilia Key Terms • organs of equilibirum • Sensory organs that respond to body position and motion • vestibular apparatus • System of fluid-filled sacs and canals in the inner ear; contains organs of equilibrium • hair cell • Mechanoreceptor that is activated when movement of overlying membrane causes its hairlike cilia to bend Organs of Equilibrium • Organs of equilibrium are located in three semicircular canals and two sacs, the saccule and utricle • Rotation of the head in any combination of directions moves fluid inside the canals and sacs • Fluid pressure makes cilia bend, which deforms hair cells in the plasma membrane enough to stimulate an action potential • A vestibular nerve carries the sensory input to the brain Sense of Balance • The brain senses dynamic equilibrium (angular movement and rotation of the head) by comparing signals from semicircular canals on both sides of the head • The saccule and utricle help the brain monitor head position, how fast the head is moving in a straight line, and maintain posture (static equilibrium) Vestibular Apparatus Vestibular Apparatus semicircular canals vestibular nerve saccule utricle gelatinous membrane in a semicircular canal hair cells with their cilia embedded in membrane sensory neurons Fig 30.14, p. 497 Vestibular Apparatus semicircular canals vestibular nerve saccule utricle Fig 30.14a, p. 497 Vestibular Apparatus gelatinous membrane in a semicircular canal hair cells with their cilia embedded in membrane sensory neurons Fig 30.14b, p. 497 Vestibular Apparatus semicircular canals vestibular nerve saccule utricle gelatinous membrane in a semicircular canal hair cells with their cilia embedded in membrane sensory neurons Stepped Art Fig 30.14, p. 497 ANIMATION: Dynamic equilibrium To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE 30.9 Detecting Sounds • Many arthropods and most vertebrates can hear sounds • In land vertebrates, ear flaps capture sounds traveling through air, and internal parts of the ear sort them out Properties of Sound • Sound is a form of mechanical energy • Sounds arise when a vibrating object causes pressure waves in air, water, or some other medium • Amplitude (wave height) determines how loud a sound is • Frequency (number of waves per second) determines pitch Wave Properties of Sound Wave Properties of Sound Soft Low note Loud High note A Same frequency, different amplitude B Same amplitude, different frequency Fig 30.15, p. 498 Wave Properties of Sound Soft Low note Loud High note A Same frequency, different amplitude B Same amplitude, different frequency Stepped Art Fig 30.15, p. 498 Animation: Properties of Sound Vertebrate Hearing (1) • Human ears have three regions: • The outer ear collects sound waves • The middle ear amplifies sound waves and transmits them to the inner ear • The inner ear includes the vestibular apparatus and the cochlea: a coiled, fluid-filled structure with three ducts Key Terms • outer ear • External ear and the air-filled auditory canal • middle ear • Eardrum and the tiny bones that transfer sound to the inner ear • inner ear • Fluid-filled vestibular apparatus and cochlea • cochlea • Coiled, fluid-filled structure in the inner ear that holds the sound-detecting organ of Corti Anatomy of the Ear (1) Anatomy of the Ear (1) inner ear vestibular apparatus, cochlea outer ear middle ear pinna, auditory canal eardrum, ear bones The outer ear’s flap and canal collect sound waves. 1 Fig 30.16.1, p. 498 Vertebrate Hearing (2) • In the middle ear, sound waves are transmitted from the eardrum, through three tiny bones (hammer, anvil, and stirrup), onto the surface of the oval window, an elastic membrane that is the boundary between the middle and inner ear • The inner ear contains the vestibular apparatus and the cochlea Anatomy of the Ear (2) Anatomy of the Ear (2) oval window (behind stirrup) middle ear bones: stirrup anvil auditory nerve hammer auditory canal 2 eardrum round window cochlea The eardrum and middle ear bones amplify sound. Fig 30.16.2, p. 498 ANIMATION: Ear structure and function To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE Vertebrate Hearing (3) • Membranes divide the interior of the cochlea into three fluidfilled ducts • Pressure waves from the oval window travel through fluid in the cochlea and bend hair cells embedded in one of the cochlear membranes Anatomy of the Ear (3) Anatomy of the Ear (3) fluid-filled duct fluidfilled duct organ of Corti sensory neurons (to the auditory nerve) fluid-filled duct One coil of the cochlea in cross-section. The organ of Corti detects pressure waves in fluid-filled ducts inside the cochlea. 3 Fig 30.16.3, p. 499 Vertebrate Hearing (4) • The organ of Corti, the organ responsible for hearing, sits on the base of the membrane in the middle duct • In the organ of Corti, arrays of hair cells with specialized cilia extend into an overlying membrane • When pressure waves cause the membrane to move, hair cells undergo action potentials that travel along an auditory nerve to the brain Anatomy of the Ear (4) Anatomy of the Ear (4) hair cells of organ of Corti overlying membrane basilar membrane 4 Pressure waves cause the basilar membrane beneath the organ of Corti to move upward. The movement pushes hair cells against an overlying membrane. The resulting action potentials travel along the auditory nerve to the brain. Fig 30.16.4, p. 499 Hearing Loss • Repeated exposure to a specific loud sound can kill hair cells that respond to that sound • Hearing loss can also result from damage to the auditory nerve, loss of fluid in the inner ear, damage to the small bones of the middle ear, or even an excess amount of earwax Sound-Induced Damage to Hair Cells Key Concepts • Balance and Hearing • The ear functions in the senses of balance and hearing • In both cases, movements stimulate mechanoreceptors • In balance, body movements are the source of the stimulation • In hearing, pressure from sound waves causes movement that stimulates mechanoreceptors A Whale of a Dilemma (revisited) • Our technology has dramatically altered the sensory landscape for animals and us • Sound pollution harms animals by disorienting them, interfering with ability to find prey, or disrupting courtship • In humans, environmental noise impairs concentration, interferes with sleep patterns, raises anxiety and increases risk of high blood pressure and other cardiovascular problems Animation: Sound Detection