Case 4 Flashcards
What is the range humans detect sound in?
20Hz to 20KHz
Which range do we understand speech in?
500-4000Hz
Why is the pressure at the oval window greater than tympanic membrane?
Smaller surface area and greater force due to liquid rather than air behind it
Force on oval window is 20x more than tympanic membrane
What happens when the tensor tympani and stapedius contract?
Chain of ossicles become rigid, and sound conduction to inner ear is diminished
This is the attenuation reflex triggered by loud sounds
What is the structures of the inner ear?
Cochlear- auditory system
Labyrinth - body equilibrium (vestibular system)
What connects the scala tympani and vestibuli ?
Helicotrema
What’s special about the basilar membrane?
Base: narrow and stiff sensitive to higher frequency
Apex wide and floppy sensitive to lower frequency
What are cells and membranes of the spiral organ of corti?
Inner hair cells, outer hair cells, supporting cells
Basilar and tectorial membranes
What happens at the spiral organ of corti?
Staples tap on oval window> fluid vibrates in scala vestibuli and transfers it to scala media and basilar membrane > endolymph rushes through area between tectorial membrane and hair cells > hair cells shear against tectorial membrane > stereocilia on hair cells move towards/away kinocilium > the stereocilia have protein channels and tip links connecting the channels
What happens in the inner hair cells?
If the stereocilia moves toward the kinocilium - potassium and calcium ions move into hair cell > depolarisation > release glutamate > AP in periphery process to spiral ganglion> central process to cochleae nerve
What happens in the outer hair cells?
If loud noise - nerve from olivocochlear bundle releases Ach > binds to OHC channels > potassium ions leave the cell. > hyperpolarisation > Preston cells molecules relax > cell lengthens > basilar membrane moves down reducing vibration > decreases HC activation
To distinguish different frequencies - same as above but Preston molecules contract > decreasing cell length > HC is then activated
What is the vestibule?
Made up of outer bony labyrinth - vestibule w/ Perilymph; inner membranous labyrinth - saccule and utricule w/ Endolymph and maculae
What is the maculae?
Floor of utricle w/ stereocilia pointing upwards and in saccule with stereocilia pointing downward
What is the function of utricle and saccule?
Utricle - horizontal linear acceleration and head tilt
Saccule - vertical linear acceleration and low frequency vibration
What is the otolithic membrane?
Membrane above hair cells which contains crystallised calcium carbonate (otoliths)
How does the vestibule work?
Linear acceleration/hear tilt > otoliths pulls gelatinous membrane in direction of acceleration > hair cell stereocilia move toward/away from kinocilium > potassium and calcium ion move in/no movement > increased/decrease release of glutamate and aspartate > increased/decreased AP down the nerve
What makes up the semicircular canals?
Lateral, anterior and posterior canals
Labyrinth - outer bony semicircular Canals and inner membranous semicircular ducts
Cristae Ampullaris - sensory epithelium
What is the function of the semicircular canals?
Angular/rotational acceleration; maintain dynamic equilibrium (balance and posture)
How does the semicircular canal work?
Rotation > endolymph pushes/pulls onto ampullaris bending the gelatinous membrane (cupula) > stereocilia bends toward/away from kinocilium > depolarisation/hyperpolarisation > glutamate released/or not > AP o not down medial vestibular nucleus > excite/inhibit nucleus and contralateral my excite or inhibit CN VI nucleus > stimulate and inhibit LR of the eyes
It also contralaterally innervates CN III nucleus so excite or inhibit IR of each eyes
What is vestibular nystagmus?
Linear slow phase nystagmus (involuntary eye movements) - caused by dysfunction of the vestibular part of the inner ear, the nerve, the vestibular nucleus within the brainstem, or parts of the cerebellum that transmit signals to the vestibular nucleus
What is the auditory pathway?
Tympanic membrane > ossicles > oval window > scala vestibuli to scala media > endolymph moves hair cells > AP to cochlear branch of CN VIII > cochlear nuclei > superior olivary nuclei > lateral Lemniscus nuclei > inferior colliculus > medial geniculate nucleus > primary auditory cortex
How is the cochlear nuclei divides?
Dorsal and 2 ventral (VPC and AVC)
Dorsal Nuclei give off DAS > majority contralaterally innervate Lat. Lemniscus nucleus directly with some joining DAS and IAS to form the Lat. Lemniscus to the Lat. Lemniscus nucleus
Ventral Nuclei - AVC gives off VAS which bilaterally innervates SON and VPC gives off an IAS which goes off with DAS to innervate contralateral lat. Lemniscus nucleus (majority is direct and some go with VAS as the lat. Lemniscus from the SON
What is the function of SON?
Localisation - lateral is for determining the relative intensity of sound stimulus and medial is for relative timing of sound stimulus
The olivocochlear bundle inhibit basilar membrane vibration
What is the pontine reticular formation?
It helps us become more alert of volume by innervating CN V (tensor tympani) and CN VIII (stapedius) to cause dampen sound
What is aphasia?
Inability to speak, write or understand written or spoken word due to lesion in the brain
What does wernicke’s and broca’s areas do?
Wernicke’s is si understanding sound as words
Broca’s for creating works by moving muscles
What is the Sylvain fissure?
It is the fissure which information from broca’s and wernicke’s areas are transferred via articulate fasciculus
What are the four types of aphasia and cause?
- Sensory (receptor) - lesion in wernicke’s; can’t understand sentences but speech is not impaired
- Motor (expressive) - lesion in Broca’s; problème formulating words
- conductive - lesion innarcuate fasciculus; understand and speech is cool but order is messy
- global/central - issue with both broca’s and wernicke’s
What is Otitis Media?
Inflammatory condition of the middle ear that results from dysfunction of the Eustachian tube as a result of inflammation of the mucous membranes / adenoid tonsils only nasopharynx
What cause Otitis Media?
URI or an allergy
What is the result of Otitis Media?
Negative pressure in middle ear causing fluid from surrounding tissues to be sucked into the middle ear cavity causing effusion
What is acute otitis Media?
Results when pathogens from nasopharynx infect the inflammatory fluid collected in middle ear
What are signs and symptoms of acute middle ear infection?
Erythematous (inverted) tympanic membrane, bulging or retracted and occasionally spontaneously perforated
Diminished hearing, fever, malaise or irritability
What is the treatment of acute otitis media?
amoxicillin - penicillin Antibiotic
What is recurrent Acute Otitis Media?
More than 3 episodes within 6 months or 4 within 1yr due to re-infection
Treated with antibiotic prophylaxis (prevents recurrences)
When does otitis Media with effusion usually resolve?
2-4weeks by them self
What is the treatment for Otitis with effusion?
Grommet (tympanostomy tube) - tube on tympanic membrane to ventilate middle cavity
As the tympanic membrane heals the grommets fall out
What is Ménière’s disease?
Inner ear disease characterised by recurring episodes of rotator vertigo, deafness and buzzing in the ear (tinnitus) and vomiting and loss of balance
Due to build up of endolymphatic fluid in inner ear
How is Ménière’s disease treated?
Vestibular sedatives
Low salt diets and avoidance of caffeine to prevent it
Labyrinthectomy- perfuming round window orifice with ototoxic drugs e.g. gentamicin (destroys vestibular epithelium)
What is the two associations of hearing loss?
Recessive inheritance - congénital hearing loss
Dominant genes - onset in adolescences or adulthood
What are the two types of hearing loss?
- conductive: outer and/or middle ear problem with conducting waves due to earwax, otitis externa, TM perforation/retraction, acute otitis media or w/ effusion
- sensorineural: inner ear problem due to poor hair cell receptor growth, noise trauma and infection, deafness genes
How can conductive hearing loss be treated?
Hearing aids, antibiotics, cochlear implants
What are the two ways attention is mediated?
Top-down: from information we know we then add the information from senses
Bottom-up: process sensory information as they come and then converting them to thoughts
Which lobe governs attention?
Parietal lobe
Left - governs that of the right body
Right - governs both sides
Where is the visual association cortex?
Temporal lobe
What is agnosia?
Difficulty recognising, identifying, and naming different categories of objects
What happens in a frontal lobe lesion?
The individual loses the maintenance of their personality
What percentage of deaf people are over the age of 60?
90
What are the effects of deafness and hearing impairment on individual and society?
Effects development of speech, language and cognitive skills in kids
Slow progress in school
Hard to keep a job
Social isolation and stigmatisation
Risk of depression
Anxiety and reduced motivation
What is post-lingual deafness?
Deafness following speech development
What is pre-lingual deafness?
Loss of hearing prior to speech development
What is hearing loss?
Description of level of hearing lost (pre or post lingual)
What is hard hearing?
Someone with some degree of hearing loss
How many deaf children are born in hearing family?
90%
What are the different identifies for hearing?
Culturally hearing: deafness seen as disability to overcome
Culturally marginal: doesn’t fit in with hearing or deaf culture
Culturally deaf: positively accept deafness
Bicultural: mixture of deaf and hearing environment
When does critical period for first language acquisition end?
Between 4-12yrs old
When do children tend to start talking?
1yrs old
At what age does speech of kids sound more like adults?
4yrs old
