HESP311 Exam 2 Study Guide 1 What are the major divisions of the osseous labyrinth Bony Cochlea Bony Vestibule Bony semicircular canals 3 2 Name the three semicircular canals Superior Posterior Lateral 3 The orientation of the semicircular canals permits detection of rotational movement in any direction 4 The oval window can be found on the lateral wall of the vestibular cavity while the posterior wall contains the entrances and exits to the SCC s The superior and the inferior walls have no important landmarks 5 Which of the following is NOT found on the medial wall of the vestibular cavity a Elliptical recess b Pyramidal eminence c Endolymphatic aqueduct d Tiny perforations for nerve fibers to pass 6 The anterior wall houses the opening to the cochlea 7 The utricle saccule can be found in the elliptical recess while the utricle saccule is found in the circular recess 8 The cochlea has 2 turns in humans and when stretched out it is 35 mm long 9 Which of the following is NOT one of the bony cochlear turns a Basal b Medial c Lateral d Apical 10 The core of the bony cochlea is called the modiolus 11 The bony shelf that projects from the medial wall of the cochlea and semi divides the cochlea into compartments the scala vestibuli and the scala tympani is called the osseous spiral lamina 12 Perforations along the osseous spiral lamina are known as habenula perforata 13 The spiral ganglion is the collection of nerve fibers found within the modiolus 14 The cochlear aqueduct is the opening in the basal turn of the cochlea Perilymph flows through the aqueduct 15 Perilymph is secreted by the epithelial membrane and fills all spaces SCC vestibule scala tympani and scala vestibuli of the bony labyrinth 16 Perilymph is high in Na and low in K 17 What is the function of perilymph cochlea Protect sensory receptors in the membranous labyrinth and transmit sound pressure variations in the 18 Inside the bony labyrinth the membranous labyrinth contains six main structures including three membranous semicircular canals the utricle the saccule and the cochlear duct also known as the membranous cochlea 19 The three membranous semicircular canals hook into the utricle saccule and the cochlear duct connects to the saccule via the ductus reuniens 20 The endolymphatic duct allows the utricle and saccule to communicate 21 The endolymphatic sac produces endolymph which is high in K low in Na and fills the membranous labyrinth 22 Cristae maculae are located in the ampulla of the semicircular canals while cristae maculae are located in the utricle and saccule 23 The Basilar membrane makes up the floor of the membranous cochlea while Reissner s membrane makes up the ceiling Both membranes attach to the spiral ligament 24 The outer wall of the membranous cochlea is lined with stria vascularis a rich capillary bed that serves as the blood supply to the cochlea 25 The sensory end organ for hearing is the Organ of Corti 26 The membranous cochlea is slightly shorter than the bony cochlea and allows for communication between scala tympani and scala vestibuli via the helicotrema 1 Label the following with either O outer hair cell or I inner hair cell I Flask shape O Test tube shape O Cilia forms W I Cilia forms U O Cilia filled with actin O 12 000 15 000 present I 3 500 present O 3 5 rows in the cochlea I 1 row in the cochlea O Contains 100 200 cilia per cell O Supported at the base by deiters cells I Contains 40 60 cilia per cell O Nucleus is contained in the lower 1 3 of the cell O Subsurface layers contain calcium and prestin I Completely supported at the base and sides 2 The lower boundary of the organ of Corti is a Reissner s membrane b Basilar membrane c Reticular lamina d Deiter cells 3 The reticular lamina is a stiff plate that covers the hair cells and isolates them from endolymph 4 The tectorial membrane is a non cellular gelatinous mass located above the reticular lamina that is strongly attached to the spiral limbus on the medial side and weakly attached to the Hensen cells on the lateral side 5 The artery is the main arterial supply to the inner ear a nucler b modiolar c sensorineural d cochlear 6 The cochlear artery supplies the stria vascularis which directly indirectly supplies blood to the inner ear by regulating the composition of endolymph Why is this important for hearing This is important because otherwise you would hear the blood rushing in your ear if there was direct contact with the blood suppy 7 The Labyrinthine artery is an end artery meaning that there is no collateral circulation to the inner ear 8 What is the traveling wave The bending of the cochlear partition bending up and down due to the differences in pressure of fluid above and below the partition moves from base to apex 9 A low high frequency stimulus causes maximum displacement at the base while a low high frequency stimulus causes maximum displacement at the apex 10 Why is the cochlear partition called a mechanical frequency analyzer It analyses the incoming signal according to its frequency 11 Describe the differences between the basilar membrane at the base vs at the apex of the cochlea Base narrow stiff less mass high frequencies Apex wide flexible more mass low frequencies 12 The stereocilia of the outer hair cells bend due to the contact with the tectorial membrane while the stereocilia of the inner hair cells bend due to drag of fluid because they don t come into contact with the tectorial membrane 13 Describe the transduction process of the inner hair cells The bending of the inner hair cell s stereocilia causes the tip links to bend and contract When the tip link of the longest cilia stretches the trap door opens and allows ions to enter the hair cell through the cuticle free pore A receptor potential is generated at the top of the hair cell and is carried to the bottom of the cell to act on pre synaptic structures This causes the release of glutamate which is then absorbed by a neuron underneath the hair cell and initiates impulses 14 The afferent neurotransmitter released by the inner hair cells is called glutamate 15 The protein that allows tip links to move is myosin 16 The reverse traveling wave from the feedback mechanism of the outer hair cells is transmitted back to the external auditory canal in a measurable product called a Synaptic transduction b Endocochlear potential c Auditory brainstem response d Otoacoustic emissions 1 Define electrical potential The difference in electrical charge that exists between