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Audition: The sense or act of hearing. Two bundles of aging outer hair cells showing severe degeneration. The outer hair cells are responsible for fine tuning and amplifying the sounds that are detected by the inner hair cells. This age-related degeneration of hair cells is responsible for the hearing loss often associated with aging. The Ear Outer Ear: Pinna. Collects sounds. Middle Ear: Chamber between eardrum and cochlea containing three tiny bones (hammer, anvil, stirrup) that concentrate the vibrations of the eardrum on the cochlea’s oval window. Inner Ear: Innermost part of the ear, containing the cochlea, semicircular canals, and vestibular sacs. There are two theories…….. Theories of Audition Helmholtz Place Theory suggests that sound frequencies stimulate the basilar membrane at specific places resulting in perceived pitch. http://www.pc.rhul.ac.uk Frequency Theory states that the rate of nerve impulses traveling up the auditory nerve matches the frequency of a tone, thus enabling us to sense its pitch. Sound Frequency 100 Hz 200 Auditory Nerve Action Potentials Conduction Hearing Loss: Hearing loss caused by damage to the mechanical system that conducts sound waves to the cochlea. Sensorineural Hearing Loss: Hearing loss caused by damage to the cochlea’s receptor cells or to the auditory nerve, also called nerve deafness. Older people tend to hear low frequencies well but suffer hearing loss when listening for high frequencies. Cochlear implants are electronic devices that enable the brain to hear sounds. Wolfgang Gstottner. (2004) American Scientist, Vol. 92, Number 5. (p. 437) EG Images/ J.S. Wilson © Deaf Musician Cochlear Implant Because we have two ears, sounds that reach one ear faster than the other ear cause us to localize the sound. Smell and Taste What is the bigger question here? Nature versus Nurture Traditionally, taste sensations consisted of sweet, salty, sour, and bitter tastes. Recently, receptors for a fifth taste have been discovered called “Umami”. Sweet Sour Salty Bitter Umami Meaty/cheesy Lets take a look at the Nature perspective first. •Taste (and smell) are chemical senses. What is the central muscle involved in taste? Those bumps on our tongue are called Papillae. Papillae help grip food while your teeth are chewing. They also have another special job they contain your taste buds Surface of the tongue chemicals, which are the stimuli for taste, break down into molecules molecules mix with saliva an run into narrow trenches on the surface of the tongue molecules then stimulate the taste buds Gustation: the process of tasting SEM Taste bud on fungiform papilla, close-up Scanning electron micrograph of close-up of a taste bud on a fungiform papilla on the tongue, computer-coloured red./pink. Taste buds shaped like miniature onions receptors for taste chemicals dissolved in saliva activate taste buds produce nerve impulses that reach areas of the brain’s parietal lobe brain transforms impulses into sensations of taste Gustatory Pathway Figure 15.2 When one sense affects another sense, sensory interaction takes place. So, the taste of strawberry interacts with its smell and its texture on the tongue to produce flavor. Taste is 80% smell. Like taste, smell is a chemical sense. Odorants enter the nasal cavity to stimulate 5 million receptors to sense smell. Unlike taste, there are many different forms of smell. Stimulus we smell volatile substances volatile substances are released molecules in the air at room temperature example: skunk spray, perfumes, warm brownies; not glass or steel 4 Primary Odors • acid sour • burnt • fragrant sweet • caprylic rancid, rotten Not in text Olfactory cells receptors for smell are located in a I-inch-square patches of tissue in the uppermost part of the nasal passages. olfactory cells are covered in mucus which volatile molecules dissolve and stimulate the cells the cells trigger nerve impulses that travel to the brain which interprets the impulses as different smells (some 10,000 or so) Sensory adaptation don’t smell own perfume, sweat, … Cilia: Nose Hairs Sense of Smell Figure 15.3 The brain region for smell (in red) is closely connected with the brain regions involved with memory (limbic system). That is why strong memories are made through the sense of smell. Ability to identify smell peaks during early adulthood, but steadily declines after that. Women are better at detecting odors than men. Can you smell the difference between? Well….yes and no. Pheromones •Chemical messengers that are picked up through our sense of smell. •Founded in the early 1930’s by studying silkworms. •Jury is still out on whether they exist in humans. Best evidence we have comes out of the university of Chicago. to intensify the taste of food to warn of potentially dangerous foods elicit strong memories; emotional feelings Somesthetic Senses Soma body Esthetic feeling Touch Kinesthetic Vestibular Bruce Ayers/ Stone/ Getty Images The sense of touch is a mix of four distinct skin senses—pressure, temperature (warmth & cold), and pain. Only pressure has identifiable receptors. All other skin sensations are variations of pressure, warmth, cold and pain. Pressure Burning hot Vibration Vibration Cold, warmth and pain The Tactile Senses Touch Skin receptors that make us aware of how & where we’re being touched. Pressure Receptors beneath the skin that make us aware of deeper touch. Temperature Receptors are found just beneath the skin to give the sensation of hot, cold, and warm. somatosensory cortex located in the parietal lobe Pain tells the body that something has gone wrong. Usually pain results from damage to the skin and other tissues. A rare disease exists in which the afflicted person feels no pain. AP Photo/ Stephen Morton Ashley Blocker (right) feels neither pain nor extreme hot or cold. Melzak and Wall (1965, 1983) proposed that our spinal cord contains neurological “gates” that either block pain or allow it to be sensed. Gary Comer/ PhototakeUSA.com Pain can be controlled by a number of therapies including, drugs, surgery, acupuncture, exercise, hypnosis, and even thought distraction. Todd Richards and Aric Vills, U.W. ©Hunter Hoffman, www.vrpain.com Receptors located in our skin. Three sensations? Touch, pressure, temperature Gate Control Theory of Pain The sense of our body parts’ position and movement is called kinesthesis. The vestibular sense monitors the head (and body’s) position. Bob Daemmrich/ The Image Works http://www.heyokamagazine.com Whirling Dervishes Wire Walk Grace and Balance The Kinesthetic Sense Keeps us informed about movement of body parts & their position in relation to each other. Muscle Movement, Posture, & Joints Information comes from stretch receptors, the tendons, & the internal organs. Tells us where our body parts are. Receptors located in our muscles and joints. Without the kinesthetic sense you could touch the button to make copies of your buttocks. Balance & Equilibrium Vestibular Sense • keeps us informed about • balance & the position of our body in space. Hair cells in the inner ear bend in relation to the position & movement of the head giving information that the brain uses to help us maintain our balance and to sense changes in our movement through space. Tells us where our body is oriented in space. Our sense of balance. Located in our semicircular canals in our ears.