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PSYCH 261 (91)


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University of Waterloo
Deltcho Valtchanov

Audition, the Body Senses and the Chemical Sense Chapter 7 The stimulus *Pitch – frequency of vibration measured in hertz. *Loudness – function of sound wave intensity; wave increase in appitude when it is loud, decrease in appitude when it is soft *Timbre – provides information about the nature or complexity of the sound; how many waves combine a specific sound *Different species hear over different frequency ranges Anatomy of the ear *Pinna – external ear.; tunnel sound to the ear cannal *Tympanic Membrane – eardrum; vibrates when it hears sounds; as the tympnaic membrane vibrates, it causes the ossicles to vibrate into something else in to the cochlea *Middle Ear – hollow region containing the ossicles, between the tympanic membrane and the cochlea. *Ossicles – middle ear; where hammer - causes the cochlea to move; *Ear drum – as the ear drum vibrates, it causes the ossicles to start moving and converting the sound in to the cochlea bones. *Malleus (hammer) – connected to ear drum *Incus (anvil) - no *Stapes (stirrup) - no need to know the latin names *Cochlea – snail-shaped structure of the inner ear containing the organ of Corti. *Organ of Corti – sensory organ for the auditory system. *Basilar Membrane – a gel like substance embedded with tiny little hairs *Hair Cells *Tectorial Membrane *Oval window – opening in the cochlea where stapes is located *Round window – opening in the cochlea where pressure’s equalize Basilar membrane responses to sound Auditory hair cells *Cilia – hairlike appendage of a cell involved in movement or in transducing sensory information; found on the receptors in the auditory and vestibular system. Auditory hair cells *Tiplink – elastic filament that attaches the tip of one cilium to the side of an adjacent one. Primary Auditory Pathway *Cochlea nerve *Branch of auditory nerve *Cochlea nucleus *Nuclei in medulla *Superior Olivary Complex *Receives info from cochlea nuclei *Lateral Lemniscus *White matter fibres carries information through medulla and pons *Inferior Colliculus *Orienting responses *Medial Geniculate Nucleus *Thalamic nucleus relays info to cortex Perception of Pitch *Place Coding *Coding of frequencies by different locations on the basilar membrane. *Membrane is maximally deformed at distinct locationsby different frequencies * Higher frequency Sounds encoded *Closer to the oval window; Lower frequency Sounds encoded farther Cotra- and Ipsilateral projections Perception of Loudness *Rate Coding *Coding of frequencies by the rate of firing of neurons in the auditory system. *Achieved by alterations in the rate of firing of cochlear nerve axons. *Louder sounds produces more stimulations in the cilia *** Place coding detects higher frequencies; rate coding detects lower frequencies Perception of Timbre *Fundamental Frequency – lowest, and usually most intense, frequency of a complex sound; most identifiable part of the sound; lowest frequency within the complex sound *Overtone – frequency of complex tones that occurs at multiples of the fundamental frequency. Spatial Localisation *Phase Differences *Difference in arrival times of sound waves at each eardrum. *Model of a coincidence detector Echo-locators Using sound “reflections” to localise objects – much like bats use sonar. Complex Sounds *Perception of Environmental Sounds and Their Location *Pattern Recognition – recognition that particular patterns of constantly changing activity belong to different sound sources. *Visual and auditory info are processed beside each other *Complex sound perception is conducted by circuits of neurons in the auditory cortex. Vestibular System *Receptor Cells *Hair Cells – found in the semicircular canal and vestibular sacs. *Vestibular Pathway *Eighth cranial nerve (2 branches): *Vestibular Nerve *Cochlear Nerve Vestibular ocular reflex Vestibular System *Functions include *Balance *Head position *Eye-head co-ordination *Low frequency stimuluation of the sacs can cause nausea *Stimulation of the canals can cause dizziness Somatosensation – sensation from the physical world; sensations encoded by the receptors of the skin *Cutaneous Senses – skin senses; Pressure - *Vibration *Temperature *Tissue Damage (Pain) *Proprioception – perception of body position and posture; e.g. if you close your eyes, you could still touch your two fingers together (where the body’s position in space) *Kinesthesia – perception of body’s own movements. (where the body is moving towards or movement itself) Somatosenation *The Sensory Homunculus Somatosensation – SHORT ANS!!! NAME THE 4
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