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Sensation: Hearing and Other Senses A P P SYCH MS . BROWN M YE RS, CH. 5 Audition & the Ear Audition – the sense/act of hearing We hear via sound waves ◦ Loudness – amplitude (height) of wave ◦ Measured in decibels – dB ◦ Loud sounds have high amplitudes ◦ Softer sounds have smaller amplitudes Audition – the sense/act of hearing ◦ Pitch – a tone’s experienced highness or lowness, depends on frequency ◦ Frequency – number of wavelengths that pass a point in a period of time ◦ Low pitch/frequency sounds = bass ◦ High pitch/frequency sounds = high ringing Outer Ear Pinna – outer ear/lobe External auditory canal – channels sound waves to the eardrum Middle Ear – eardrum, 3 bones Eardrum – thin membrane that vibrates when a sound waves hits it ◦ Vibrations felt by 3 small ossicle bones – hammer, anvil, and stirrup – and sent to inner ear Inner Ear - cochlea, semicircular canals, and vestibular areas Cochlea – a coiled, bony, fluidfilled tube in the inner ear through which sound waves trigger nerve impulses ◦ Moving fluid in cochlea triggers hair cells in the cochlea’s basilar membrane stimulates neurons to produce electrical impulses Auditory nerve – sends neural impulses from the cochlea to the brain (thalamus temporal lobe) Hearing Animation Audition and Pitch Theories Cochlea Animation How Do We Hear Pitch? PLACE THEORY (HELMHOLTZ) Links the pitch we hear with the place where the cochlea’s membrane is stimulated High pitch sounds FREQUENCY THEORY The rate of nerve impulses traveling up the auditory nerve matches the frequency of a tone, thus enabling us to sense its pitch Low pitch sounds We use both theories to hear all pitches. Locating Sounds Distance between ears allows us to place sounds in space. Equidistant sounds – cock our heads to distinguish location Hearing Loss Conduction ◦ Damage to the mechanical elements (eardrum, H, A, or S) that conduct sound waves to the cochlea Sensorineural ◦ Damage to the cochlea’s receptor cells or to the auditory nerve, also called nerve deafness ◦ Hearing can be slightly restored with a cochlear implant (if there is a healthy nerve) ◦ Device for converting sounds into electrical signals and stimulating the auditory nerve through electrodes threaded into the cochlea. ◦ Must have a functioning auditory nerve Cochlear Implants Pro Experience sounds and oral communication Helps deaf children with talking Children who rely solely on ASL before learning to speak have more difficulty learning to read and write later in life Con Deafness is not a disability ASL is a complete and functioning language Deafness ≠ linguistically impaired Sensory Compensation People who lose one channel of sensation often compensate for it with a slight enhancement of other sensory abilities Also a product of brain plasticity Other 3 Senses OLFACTION, TASTE, TOUCH Olfaction – sense of smell Chemical sense - Odors are composed of chemical molecules which are sensed by olfactory receptor cells at the top of the nasal cavity. Receptors in nasal cavity (transduction) olfactory bulb olfactory nerve primary smell cortex (temporal lobe) ◦ only sense not to pass through the thalamus Olfaction and Memory/Emotion Odors invoke memories or feelings because the part of the brain that interprets odors is directly linked with the limbic system which processes memories and emotions Wrong Gustation – Sense of Taste Evolutionary purpose – survival 5 basic tastes ◦ ◦ ◦ ◦ ◦ Sweet Salty Sour Bitter Umami (best experienced by the flavor enhancer MSG, most commonly found in Asian food – described as “savory”) Gustation - Taste Chemical sense – taste buds (200+ per bump on tongue) catch food chemicals via receptor cells ◦ Receptor cells can be more sensitive to different tastes Receptors on taste buds (transduction) facial nerve meduala thalamus primary gustatory region (temporal lobe) Sensory Interaction The principle that one sense may influence another, as when the smell of food influences its taste ◦ To savor taste we normally breathe the aroma through the nose ◦ Sight of spoken words and the audition of spoken words influence each other Vision and audition ◦ We use the auditory info from the sound of words and the visual info from the moving of the mouth to quickly comprehend speech. ◦ However, this sensory interaction can also lead us astray… Flavor Combination of odor, texture, temperature, and taste ◦ “taste blindness” – lack of sensitivity to certain taste ◦ Sensitivities can be inherited Tea Flavors Chocolate Flavors Touch - Skin Senses 3 distinct skin senses ◦ ◦ ◦ ◦ Pressure Temperature Pain These senses are combined to produce sensations such as: hot, tickling, itchy, wetness, etc Only the sensation of pressure has specialized nerves in the skin; the rest of the nerve endings can feel warmth, cold, and pain in various combinations Skin receptors (transduction) nerves (PNS) spinal cord (CNS) medulla thalamus sensory cortex Pain: Gate-Control Theory The spinal cord acts as a gate that controls if pain signals reach the brain. ◦ Small nerve fibers conduct pain signals, while larger neural fibers conduct most other sensory signals. ◦ When tissue is injured, the smaller nerve fibers activate and open the neural gate to send pain to the brain. ◦ Larger-fiber activity closes the pain gate, turning pain off. Using this theory, people believe that activating large neural fibers can block pain ◦ Ex: acupuncture ◦ Ex: rubbing painful areas stimulates large neural fibers than can block pain ◦ Ex: electrical stimulation of painful area Pain Something is WRONG! Biological •Activity in spinal cord’s large and small fibers (gate-control theory) •Genetic differences in endorphin production •The brain’s interpretation of CNS activity Psychological •Attention to pain •Learning based on experiences •Expectations of pain Perception of Pain Social Cultural •Presence of others •Empathy for other’s pain •Cultural expectations Pain Control Pain can be treated physically and psychologically ◦ Drugs, surgery, acupuncture, electrical stimulation, massage, exercise, hypnosis, relaxation training, thought distraction, etc ◦ Because pain is perceived in the brain, diverting the brain’s attention can bring relief th 6 The and Senses th 7 KINESTHESIS AND VESTIBULAR SENSE Kinesthesis AKA Proprioception The system for sensing the position and movement of individual body parts ◦ Enabled by millions of proprioceptors in muscles, tendons, and joints Proprioceptors (transduction) nerves spinal cord brain (cerebellum) Vestibular Sense The sense of body movement and position, including the sense of balance ◦ Monitors the head’s position which usually dictates what the body is doing Fluid in semicircular canals hair cells in vestibular sacs vestibular nerve brain (medulla and cerebellum) Crash Course - Sensation