OS III Exam II Flashcards
What are the major landmarks of the auricle?
Helix, anti-helix, tragus, anti-tragus, lobule, concha.
Where are the ceruminous glands and what do they produce?
Modified apocrine glands that produce cerumen (a lipid based secretion). Different from ear wax which is a combination of cerumen and sloughed skin cells and sebaceos secretions.
What nerves innervate the inner and outer surfaces of the tympanic cavity?
The outer surface is inervated namely by V3 of the trigeminal superiorly, the vagus inferiorly. The inner surface is innervated by the glosspharyngeal (IX).
How does swallowing equalize pressure in the middle ear?
Swallowing opens the eustachian tube. It is the only opening in this closed compartment.
Describe the Eustachian tube and what muscles open it.
Cartilagenous tube that connects the tympanic cavity to the nasopharynx. Opened by levator and tensor palati, and salpingopharyngeus.
Describe the ossicles, their attachments and their significance in transmission of sound.
The ossicles convert vibrations in the tympanic membrane (air) into mechanical vibration. The malleus attaches to the incus to the stapes. The stapes transmits the vibration through the oval window into the cochlea.
Where are the tensor tympani and stapedius muscles, to what do they attach and what do they do?
Tensor tympani (V3 of trigeminal) attaches to the malleus and stapedius (facial, VII) to the stapes. Both muscles dampen vibration.
Describe the chorda tympani in terms of: source, how it passes through the tympanic cavity, and its function.</p>
It branches off of the facial nerve (VII), passes between the malleus and tympanic membrane. , exits, and joins V3 as it approaches the oral cavity. Contains sensory and autonomic axons. Sensory mediate taste to anterior 2/3 of tongue. PNS to salivary glands (submandibular and sublingual).
Where does otitis media occur?
Middle ear, can impact the chorda tympani. Fluid builds up, causing influx from the nasopharynx.
What is the tegmen tympani and its significance in spread of infection?
It is a small layer of bone between middle ear and cranial cavity, if disrupted by infection can cause meningitis or brain abscess.
What is cholesteatoma?
Skin from the ear canal fills with cysts and migrates to perforate the tympanic membrane.
Describe the spaces in the cochlea.
Helical bony canal dividid into three spaces: cochlear duct, scala tympani, scala vestibuli.
Describe the cochlear duct in terms of membranes, windows and fluid.
Membranous duct that encloses the organ of Corti, seperate from scala tympani and vestibuli. Stapes vibrates perilymph at oval window while the round window absorbs outward displacements of fluid vibrations at the end of the cochlea.
What is the difference between perilymph and endolymph?
Perilymph: in the scala vestibuli and tympani and is higher in Na. Endolymph: secreted by the stria vascularis and has a high K+ content and low Na+. Limited to the cochlear duct.
Describe the organ of Corti in terms of location, cell types, relation to the tectorial membrane.
Epithelial layer on the basilar membrane, covered by the tectorial membrane. Inner and outer hair cells respond to movement of the tectoral membrane. Vibration of the basilar membrane against the tectoral membrane, stimulates stereocilia. Hair cells activate sensry neurons of the cochlear nerve.
What is the difference between the inner and outer hair cell in terms of location, function?
Inner hair cells lie closer to the folcrum of the basilar and tectorial membranes are the primary sensory cells. Outer hair cells lie futher out and act more like mechanical amplifier.
What is the difference between the inner and outer hair cell in terms of innervation, and impact on sound reception?
Inner hair cells project information to the cochlear nerve. Outer hair cells enhance weak auditory signals via electromotile response, small sensory nerve contribution (5%)
How does the cochlea encode sound frequencies?
Frequencies are differentiated according to how flexible the basilar membrane is and width of base to apex. Tonopic: spacial representation of sound. Each frequency has a maximal amplitude at a certain location of the basilar membrane where it generates an impulse.
What are the major brain stem steps by which sound information reaches the cortex?
Medullary auditory nuclei project up the lateral meniscus to the inferior colliculus to the medial geniculate to the primary auditory cortex (temporal lobe)
How does the superior olive localize sound?
<p>olive. It notes disparity in time and intensity between R & L sounds to localize the object. Time difference localizes low frequencies, while intensity difference localizes high frequencies.
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Describe the anatomy and impact of superior olivary feedback onto the organ of Corti.
Efferent olivocochlear neurons from the superior olive regulate hair cell sensitivity and electormotile response. Applies in quiet and noisy situations, that allow low level sound detection and improved discrimination respectively.
What is efferent superior olivary feedback stimulated by?
Sensory input from cochlear nuclei, reticular formation, auditory cortex (influenced by limbic systme).
Describe the location and function of the primary auditory cortex.
Located in the superior temporal lobe, tontotopic organization of frequencies synthesized into sound forms.
What is the importance of the inferior colliculus?
Projects sound to cortex and motor through cranial nerve tracts (associated with orientation of the head and other regions for sound localization).
What is tinnitus?
Sensation of sound without external stimulus.
Compare subjective and somatic types of tinnitus.
Subjective: phantom auditory perception. Somatic: sound produced by excitatory stimulus to the cochlear nerve within the nervous system. Somatic is a type of subjective.
What are the dorsal and ventral streams of cortical processing of auditory information? What are their functions?
Dorsal stream: where. projects to parietal-temporal junction and frontal lobe, broca’s area, left dominant. Ventral stream: speech comprehension, Wernicke’s area (key language are), bilateral.
How is music processed in the cortex?
All of the cortices are involved, but asymmetrically. Singing employs more activation in the right auditory region of temporal lobe. Modulates activity in limbic system :amygdala, insula, hippocampus. Can stimulate visceromotor system.
What are the different regions of the membranous labyrinth? </p>
Semicircular ducts (within the semicircular canals), saccule & utricle (within the vestibule)
Where are the perilymph and endolymph?</p>
Perilymph is produces by the periosteum and drains into CSF via the perilymphatic duct. Endolymph is secreated by the cochlear duct and drains into the dural sinuses via the endolymphatic duct.
What is Meniere’s disease and what causes it?
Transiet vertigo, nausea, vomiting, abnormal saccadic eye movements. Excess endolymph and fluid pressure affect receptor function.
Describe the structure and function of the crista.
The crista is the receptor in each semicircular canal ampulla. It is comprised of hair cells that make up a gelatinous mass, cupula. Each hair cell has a primary kinocilium and several stereocilia.
How does endolymph move?
It doesn’t move. It maintains position. E.g. walking with a soup bowl
What is detected by the semicircular ducts?
Relative motion of endolymph during head rotation.
