7 - The Auditory Sense(3 Dimensions of Sound The s s s...

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Unformatted text preview: The Auditory Sense (3 Dimensions of Sound) The s s s Pitch - perception of the frequency of a sound wave – Maximum human range is 20 to 20,000 Hz Loudness - perception of the amplitude (intensity) of a sound wave – Measured in decibels (db) Timbre - the purity of a sound The Ear The The Ear The s 3 sections: – Outer ear (pinna, external auditory canal, tympanic membrane) tympanic – Middle ear (tympanic membrane, ossicles, to the oval window) to » malleus, incus, stapes – Inner ear (includes the cochlea and the vestibular system) vestibular The Organ of Corti The s Primary receptor unit in cochlea – Hair cells in basilar membrane – Hairs or cilia are attached to tectorial membrane ...The Organ of Corti ...The s Outer hair cells – Broad range of sound intensity – Result from bending by the tectorial membrane ...The Organ of Corti ...The s Inner hair cells – Only respond to 50-60 db+ sounds – Results from fluid movement Transduction of Sound Waves into Neural Impulses Neural s Excitation of auditory Excitation receptors – Bending of cilia ...Transduction of Sound Waves into Neural Impulses Neural s s s s Opening of K+ ion channels Influx of K+, resulting in membrane depolarization Influx of Ca++, which results in neurotransmitter release Cilia return to original position - K+ ion channels close Pathways of the Auditory Cortex Pathways Pathways of the Auditory Cortex Pathways •Hair cells •Spiral ganglion cells •Cochlear nerve •Auditory nerve •Cochlear nuclei of the medulla •Superior olivary nucleus •Inferior colliculus •Medial geniculate nucleus •Auditory cortex •Secondary auditory cortex Detection of Frequency Detection s s Place theory of pitch (Helmholz) – Basilar membrane varies in width & Basilar thickness thickness – Von Békésy's research confirmed Frequency theory of pitch (Rutherford) – Whole basilar membrane vibrates at Whole rate of stimulus frequency rate – Up to 4000 Hz – Beyond that place theory accounts for Beyond frequency frequency Detection of Amplitude Detection s s High frequency sounds - rate of receptor responding Low frequency sounds - number of neurons firing Detection of Complexity Detection s s s s Pure tones - one frequency Complex tones - 2 or more Complex frequencies frequencies Timbre or quality - refers to Timbre complexity complexity Increased complexity - relates to Increased broader area of basilar membrane activation activation Sound Localization Sound s s Time cues - reach each ear at Time different times different – Fibers cross in trapezoid Fibers bodies to each superior olive olive – Information at this level is Information important for sound localization localization Intensity cues - intensity of Intensity sound is greater for closer ear ear Role of the Auditory Cortex in Sound Recognition Role s s s Primary auditory cortex Primary -detection of various aspects of sound of Secondary auditory cortex Secondary Wernicke's area Wernicke's – Detection of language and Detection language sounds language Auditory agnosia - can hear Auditory but can't recognize sounds but Organs of the Vestibular System Organs ...Organs of the Vestibular System ...Organs •Vestibule - static sense •Utricle and saccule •Hair cells attached to otoliths ...Organs of the Vestibular System ...Organs • Semicircular canals - rotational sense • Ampulla - enlarged area • Crista - in ampula • Cupula - hair cells in gelatinous mass Vestibular Pathways Vestibular Vestibular Pathways Vestibular s s s s s s s s s s s Vestibular receptors (hair cells) Vestibular ganglion Vestibular nerve Vestibular nuclei Cerebellum Medulla Pons Spinal cord Red nucleus Superior colliculus Temporal cortex The Somatosensory System The Touch s Pain s Temperature s Proprioception s Skin Receptors Skin Skin Receptors Skin s s s s s Pacinian corpuscles - touch Free-nerve endings - temperature, pain Meissner's corpuscles - pressure Merkel's disks - pressure Ruffini's corpuscles - vibration (not pressure) Common Characteristics of Somatosensory Pathways Somatosensory Common Characteristics of Somatosensory Pathways Somatosensory s s s s s s s s All have 3 neurons from receptor to cortex Cell body of first neuron in the dorsal root ganglia Second neuron crosses in spinal cord or brain stem All ascend in the medial lemniscus to thalamus All synapse in the ventral posteriolateral thalamic nuclei Third neuron projects to the primary somatosensory cortex Located in the postcentral gyrus Distributed according to the area of the body Distributed Dorsal Column-Medial Lemniscal System Dorsal s s s s s s s Touch and proprioception Heavily myelinated neurons with cell body in dorsal Heavily root ganglia root Forms the dorsal column and ascends to the medulla Synapse with either the gracilis or cuneatus nuclei Synapse gracilis cuneatus Secondary neurons cross and form the medial Secondary lemniscus lemniscus Synapse in the ventral posterolateral thalamic nuclei Third neurons project to the primary somatosensory Third cortex cortex Anterolateral System Anterolateral – – s s s Temperature and pain Temperature Light or no myelin - cell bodies in Light dorsal root ganglia dorsal – Synapse if the substantia gelatinosa in Synapse dorsal column dorsal – Secondary neuron crosses at about Secondary the same level – Forms the lateral spinothalamic tract – Direct projections to the brainstem Direct reticular formation reticular – Some continue to the ventral Some posterolateral thalamic nuclei posterolateral – Primary somatosensory cortex Spinocerebellar system Spinocerebellar Proprioception Cerebellar cortex Spinocerebellar System Spinocerebellar s Proprioception – Cerebellar cortex The Control of Pain The s s s s Gate-control theory of pain Pain perceived only if it passes through gate in spinal cord Descending periaqueductal gray projects to spinal cord Endorphins can activate this system causing inhibition The Gustatory Sense - Sense of Taste The s Distinguishes between 4 tastes: sweet, sour, bitter, Distinguishes and salty and Gustatory Pathway Gustatory s s s s s Taste receptors 7th, 9th, and 10th cranial 7th, nerves nerves Nucleus of the solitary tract Nucleus of the medulla of Ventral posteromedial Ventral thalamic nucleus thalamic Primary gustatory cortex The Olfactory Sense - Sense of Smell The s Distinguishes between various odors Olfactory Pathway Olfactory s s s Olfactory receptors (located on the olfactory epithelium) Mitral cells of the olfactory bulbs Primary olfactory cortex (in the limbic system) ...
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