the ear Flashcards
What is neuroplasticity?
the brain’s ability to change through experience
What happens in normal hearing regarding hearing and speech?
first comes hearing then speech
What happens in post-lingual deafness regarding hearing and speech?
there is speech but no hearing (lose hearing after speech development)
What happens in pre-lingual deafness regarding hearing and speech?
no hearing and no speech
How is sound amplified in the ear?
- pinna: 10-15dB (but specific to certain frequencies)
- ear canal: 10dB
- tympanic membrane and ossicles: 18 times (due to different in surface area between the tympanic membrane and ossicles)
Where do you find endolymph (1)?
where do you find perilymph (2)?
- -cochlear duct
- semi-circular ducts - -scala vestibuli
- scala tympani
(maybe more?)
What is the chemical property of endolymph that is important in creation of AP?
high in potassium
What is sound energy?
wave form contractions and refractions in air and then fluid: causes vibrations on basilar membrane
What are the different hair cells involved in hearing?
- inner hair cells: responsible for signal transduction: have stereocillia that connect onto tectorial membrane
- outer hair cells: three rows
What happens with at basilar membrane when sound is heard?
- movement of basilar membrane: causing shearing force of hair cells onto tectorial membrane
- displacement of stereo cilia and stretch activated: ion channels open and leave potassium into hair cells and there is depolarisation of cell
What is tone?
wavelength of particular frequency (complex vibration with repetitive periodic pattern)
What is noise?
complex vibration with no repetitive pattern
What is the correlation between frequency and wavelength?
lower frequency sounds have longer wavelengths
What is the cochlear nerve pathway?
cochlear nucleus - superior olive nucleus - inferior colliculus - medial geniculate nucleus - auditory cortex
What are the important areas in the brain in regards to hearing and speech?
- primary auditory cortex
- Wernicke’s area
- Broca’s area
- motor cortex
What does Wernicke’s area do?
speech recognition and reception
What does Broca’ are do?
speech development
How do you test hearing depending on the ages?
- otoacoustic emissions (done at birth)
- auditory brainstem responses (done before 2m)
- visual reinforcement observation audiometry (6-24m)
- conditioned play audiometry (24-48m)
- conventional audiometry (over 42m)
What is the normal hearing threshold and when is it considered to be deaf?
- 0dB: normal hearing threshold
- 110dB: stone deaf
What is hearing loss due to old age called?
presbyacusis
What happens to detection of sound if you only have one functioning ear?
you can’t detect direction of sound
What is the non auditory functions of the external auditory meatus?
protecting
cleaning
+ wax waterproofs it
What are the names of the middle ear muscles
What are the functions of the middle ear muscles?
Stapedius and tensor tympani
- stiffening
- stapedius is stimulated acoustically
what are the different types of hearing pathologies?
- conductive hearing impairment
- sensory-neural hearing impairment
What does profoundly deaf mean?
related to degree of hearing loss and may be used to describe born deaf or deafened people
What does deafened mean?
people that have become deaf after acquiring spoken and written language and who mainly identifies with hearing people
What does hearing loss mean?
describe level of hearing loss
What does hard hearing/hearing impaired mean?
person with some degree of hearing loss: mainly older people who have lost their hearing through age
What are the Otolith organs comprise of? What do they detect?
- saccules
- utricles
- detect static/linear accelearation
What do they saccules detect? What are they connected to?
- vertical acceleration
- cochlea
What do the utricles detect? what are they connected to?
- horizontal acceleartion
- semi-circular canals
What are the semi-circular canals comprise of and what do they detect?
-horizontal SCC
-superior SCC
-posterior SCC
-detect angular acceleration
(to differentiate between SCC locate bifurcation between superior and posterior SCC)
In what are the sensory hair cells embedded in the otolith organs?
gelatinous layer
How is the signal created in the otolith organs?
mechanically gated membrane transduction
- otoconia: calcium carbonate crystals (striola) resting on otolithic membrane (jelly)
-jelly has receptors
–> with movement, jelly layer moves forwards
–> when stop, the crystal layer tries to move forwards which triggers receptors
(bending of the cilium causes depolarisation)
Where are the sensory hair cells located in the semi-circular canals?
ampullae
How is the signal created in the semi-circular canals?
- endolymph displaces gelatinous mass (cupula: jelly): causes physical strain on ‘hair cells’: AP
- deflection toward kinocilium increases firing, deflection away from kinocilium decreases firing
What are kin cilium?
What are stereo cilium?
in cupula of semi-circular canals
- kinocilium: tall hair cells
- stereo cilium: small hair cells
What are the different movements detected by the semi-circular canals?
- yawing motion: horizontal canals (eyes looking over shoulder)
- rolling motion: superior canals (ear towards shoulder)
- pitching motion: posterior canals (head up and down)
What is the vestibulo-occular reflex?
- prevents retinal slip, compensates for head movement
- modulated by cerebellum
what are the different phases in eye movement? and why modulates them?
- slow phase: slow drift when tracking object: modulated by vestibule-occular pathway
- fast phase: snap back to midline when stop tracking object: modulated by cerebral cortex
What is nystagmus?
alternating slow eye movement and rapid saccadic movement
What is the vestibule-spinal tract?
- medial VS tract: head position
- lateral VS tract: posture and balance
- -> both descend ipsilaterally
What is Ménière’s Disease?
increase in endolymph pressure: disrupts signal transduction and can result in tinnitus, nausea, spontaneous nystagmus
What is Benign Paroxysmal Positional Vertigo (BPPV)?
What can help?
- dislodged bits of Otolith stimulate the cupola in posterior SSC causing vertigo
- Epley manoeuvre attempts to nudge them back to the vestibule
What is motion sickness?
mismatch between data from different sensory modalities + with what the brain expects to happen
