Anatomy of the Auditory System Flashcards
Hardest bone in the human body
Bone of cochlea and vestibular labyrinth
Parts of labyrinth (3)
Vestibule, Cochlea, SCC
Round window is at which end of the cochlea
Basal
Also known as the core of the cochlea, porous bone that allows passage of auditory nerve fibers from the internal auditory meatus to the hair cell synapse
Modiolus
Separates cochlear chambers to scala vestibuli, media, tympani
Osseous spiral lamina * Also the attachment of the basilar membrane
Area where scalae communicate at the apex of the cochlea
Helicotrema
T or F: Widths of spiral lamina and basilar membrane are inversely related
T * Spiral lamina wide at base narrow at apex, Basilar membrane wide at apex narrow at base
Bony channel that allows perilymphatic fluid and CSF to communicate in the posterior fossa
Cochlear aqueduct
Thickened band of periosteum that serves as medial attachment for the Reissner membrane and gives rise to the tectorial membrane
Spiral Limbus
Tectorial membrane is a compliant gelatinous structyre composed of _______fibers.
Collagen II
How many rows of cells make up the 1)inner hair cells, 2) outer hair cells
1) one, 2) three
This supports the apices of hair cells and forms a barrier from endolymph (which is toxic to hair cells)
Reticular lamina
Distinguish perilymph and endolymph based on: 1) composition, 2) location
Perilymph (Low Key) : 1) High Na, Low K, 2) CSF/Serum; Endolymph: Low Na, High K, 2) Intracellular
This maintains ionic concentrations of endolymphatic fluid and is responsible for the metabolic environment of the scala media
Stria vascularis
Definition of enlarged vestibular aqueduct at 1) midpoint, 2) operculum
Larger than 1) 1.5mm, 2) 2mm
Enlarged vestibula aqueduct can lead to this in children, particularly after minor head trauma
Sudden, progressive SNHL
Bundles of actin filaments that are stiff hairlike structures that deflect with mechanical diaturbances
Stereocilia
Number of 1) inner hair cells in the modiolar side, 2) outer hair cells in the strial side
1) 3500, 2) 12000
Side which stereocilia are longest
Strial side * Connected stereocilia move as a unit when the longest one is deflected
Shape of 1)inner hair cells, 2) outer hair cells
1) flask, 2) cylindrical
Contents of 1) inner vs 2) outer hair cells
1) organelles like golgi bodies and mitochondria (metabolic activity) , 2) microfilaments and microtubules (motile activity)
Sites for presynaptic vesicle docking for subsequent stimulation
Synaptic bars
1) Type 1 and 2) Type 2 nerve fibers in terms of a) polarity, b) size, c) myelination, d) percentage, e) site of innervation
Type 1: a) bipolar, b) large, c) myelinated, d) 95%, e) inner hair cells; Type 2: a) unipolar, b) small, c) un- or myelinated, d) 5%, e) outer hair cells
All peripheral auditory information enters the CNS through this site, where initial auditory processing occurs
Cochlear nucleus * Located along the floor of the lateral recess of thr 4th ventricle
Dorsal cochlear nucleus
Role in orienting to sound, potential site for generation of tinnitus
Ventral cochlear nucleus
Initial processors of auditory nerve information
1) Anterior ventral vs. 2) Posterior ventral cochlear nucleus
1) large caliber, sound localization; 2) fine, frequency/spectral shape, and sound intensity
First auditory center to receive binaural innervation
Superior olivary complex
Location of the superior olivary complex
Pons
MedSuperiorOlive vs LatSuperiorOlive: interaural time delays vs intensity differences
MSO: interaural time delays; LSO: interaural intensity differences
Superior Olivary Complex 1) Ascending pathway is for? 2) Descending pathway is for?
1) Sound localization; 2) Cochlear sensitivity or tuning
Closely associated with the SOC, this also plays a role in sound localization and processing, also a component of the acoustic startle reflex pathway
Lateral lemniscus * Pathways through this correlate with wave III-V of ABR
This part receives extensive innervation from higher and lower brain regions
Inferior colliculus
Location of inferior colliculus
Midbrain
Sound localization, frequency determination, integration of auditory and nonauditory systems
Principal functions of inferior colliculus * Sound localization is also a function of Dorsal Cochlear Nucleus, Anterior ventral cochlear nucleus, Ascending SOC
Inferior colliculus is divided into 3 main neuronal groups, namely
1) central nucleus, 2) cortex, 3) paracentral nucleus
Receives non auditory information from the somatosensory system
Paracentral nucleus of inferior colliculus
Dominant region, has laminar organization, receives projections frim contralateral cochlear nucleus (direct, monaural), SOC (indirect, bilateral), lateral lemniscus (polysynaptic)
Central nucleus of inferior colliculus
Innervation is primarily from the forebrain, including primary and secondary auditory cortices
Cortex of the inferior colliculus
Other interactions of inferior colliculus: 1) associated with saccadic eye movement, 2) multiple auditory and nonauditory cortical structures
1) Superior colliculus, 2) Medial geniculate body
Portal for all ascending auditory innervation to the telencephalon
Medial geniculate body of the thalamus
Division of the medial geniculate body: 1) that has tonotopic organization, 2) plays a role in attending to acoustic stimuli, 3) largest, and plays a role in arousal to auditory stimuli
1) ventral division, 2) dorsal division, 3) medial division
Which lobe of the brain is the human auditory cortex located
Temporal lobe
Broadman area of 1) primary auditory cortex, 2) secondary auditory cortex
1) 41, 2) 42
Area for receptive language and is dominant on the left side (Eponym and Broadmann area)
Wernicke, Broadmann area 22
Cortical regions in the inferior parietal lobe that integrate auditory, somatosensory and visual information (2, name and broadmann area)
Angular Gyrus BA 39, Supramarginal Gyrus BA 40
Site for expressive language and musical syntax, left hemisphere dominant (eponym and broadmann areas)
Broca, Broadmann area 44 and 45
Also implicated in tinnitus production
Cerebellum * Dorsal cochlear nucleus also implicated in tinnitus production
Auditory cortex also projects to (3)
Medial geniculate body (cortex), SOC (brainstem), inferior colliculus (midbrain)
