PBL Topic 3 Case 4 Flashcards
How is sound energy transmitted through a gaseous, liquid or solid medium?
- Setting up vibration of the medium’s molecules
What is a decibel and why is loudness measured in this way?
- Logarithmic function of sound pressure
- The human ear can detect an enormous range of volume variations
What determines the pitch of a sound that we hear?
- Frequency
- Measured in hertz
- The faster the vibration, the higher the pitch
What is the zone of compression of a sound wave?
- Molecules are close together
- Pressure is increased
What is the zone of compression of a sound wave?
- Molecules are further apart
- Pressure is lower
How does the zone of compression affect the tympanic membrane
- Under high pressure the tympanic membrane bows inward
- The distance that it moves depends on the force that the molecules hit it, which is related to pressure and hence loudness
How does the zone of rarefaction affect the tympanic membrane
- Under low pressure the tympanic membrane bows outward
What is the role of the pharyngotympanic tube
- When open, it maintains a pressure in the middle ear that is equal to atmospheric pressure
What is the role of the ossicles of the middle ear?
- They act as a single piston
- That couple the vibrations of the tympanic membrane to the oval window.
Why is the force exerted on the oval window much greater than that exerted on the tympanic membrane?
- The total force applied to the tympanic membrane is exerted onto the oval window
- The oval window is much smaller than the tympanic membrane
- Therefore the force per unit area is much greater
What is the attenuation reflex?
- Loud sounds in the middle ear cause contraction of tensor tympani
- Tensor tympani pulls handle of malleus medially
- Stapedius moves stapes posteriorly
- Increasing rigidity in middle ear
- Reducing conduction of loud damaging sounds
Where is endolymph located and secreted, and what are its contents?
- Cochlear duct
- Secreted by stria vascularis
- High potassium and low sodium concentration
Where is perilymph located and what are its contents?
- Scala vestibuli and scale tympani
- High sodium concentration and low potassium concentration
What causes vibration of the basilar membrane?
- Movement of stapes causing oval window to bow medially
- Causing pressure waves in the scala vestibuli
- The pressure waves are transmitted across the cochlear duct
- And cause the basilar membrane to vibrate in the direction of the round window
Where does high frequency resonance occur and why?
- Near the base of the cochlea duct
- Where the basilar fibres are short and stiff
- Which vibrate better at high frequency
Where does low frequency resonance occur and why?
- Near the helicotrema
- Where the basilar fibres are long and thin
- And vibrate better at low frequency
Where is the organ of Corti located and what is its structure?
- On the surface of the basilar fibres of the basilar membrane
- A single row of larger internal hair cells
- Three or four rows of external hair cells
- Tectorial membrane
Outline how depolarisation of hair cells occurs
- Pressure waves displace the basilar membrane
- Stereocilia bend in the direction of the longer hairs
- Which causes tip links to open cation channels
- Large influx from rich endolymph from cochlear duct into the hair cell which depolarises the membrane
Outline how cochlear nerve endings are stimulated by an excited hair cell
- As a result of potassium influx
- There is opening of voltage gated calcium channels
- Which release glutamate that binds to binding sites on the afferent neurons
What is the role of outer hair cells?
- Outer hair cells sharpen frequency tuning at each point along membrane
Where are the dorsal and ventral cochlear nuclei located?
- Upper part of the medulla
Outline the projections of the dorsal cochlear nucleus to the inferior colliculi
- Project via the dorsal acoustic stria and lateral lemniscus to the contralateral inferior colliculus
Outline the projections of the ventral cochlear nucleus to the inferior colliculi
- Project via the trapezoid body to the superior olivary nucleus to the lateral lemniscus and inferior colliculi
Outline the auditory nerve pathway from the inferior colliculus to the primary auditory cortex
- To the medial geniculate nucleus of the thalamus
- From the medial geniculate nucleus through the auditory radiation to the superior temporal gyrus
Outline two brain regions that auditory nerve fibres project to that respond to loud sound
- Reticular activating system
- Vermis of the cerebellum
Outline how sound frequency is percieved in the auditory cortex and association areas
- Tonotopic maps
- High frequency sounds excite posterior neurons sounds while low frequency sounds excite anterior neurons
- Caused by lateral inhibition
What is the role of the lateral superior olivary nuclei?
- Concerned with direction sound is coming from
- By comparing the intensities of the sound reaching the two ears
What is the role of the medial superior olivary nuclei?
- Concerned with direction sound is coming from
- By comparing the time lag between the sounds entering the two ears
What are centrifugal fibres?
- Retrograde inhibitory pathways
- From the cortex to the cochlea
- Which allow attention of particular sound qualities and rejection of others
Where is Wernicke’s area located?
- Superior temporal gyrus
- Posterior to the primary auditory cortex
What is the role of Wernicke’s area in speech?
- Sensory: Interpretation of language
- Motor: Determination of choice of words to be spoken
Where is Broca’s area located?
- Prefrontal cortex
What is the role of Broca’s area in speech?
- Motor patterns for control of the larynx, lips, mouth and respiratory system that form words
What is auditory receptive aphasia?
- Inability to understnad the spoken word
What is visual receptive aphasia?
- Inability to understand the written word
What is Wernicke’s aphasia?
- Ability to understand the spoken or written word
- But the inability to understand the thought that is expressed
What is global aphasia?
- Caused by a widespread lesion from Wernicke’s area into the angular gyrus, temporal lobe and sylvian fissure
- The person is demented for language understanding or communication
What is motor / Broca’s aphasia?
- Person is able to decide what they want to say
- But cannot make the vocal system emit words instead of noises
Outline the pathway involved in hearing and speaking
- Reception in the primary auditory cortex in the superior temporal gyrus
- Interpretation in Wernicke’s area
- Determination of the thoughts and words to be spoken in Wernicke’s area
- Transmission of signals from Wernicke’s area to Broca’s area by way of the arcuate fasciculus
- Activation of skilled motor programs in Broca’s area for control of word formation
- Transmission from Broca’s area to the motor cortex to control the speech muscles
Outline the pathway involved in reading and speaking
- Reception in the primary visual area in the calcarine sulcus
- Interpretation in the angular gyrus region
- Recognition in Wernicke’s area
- Transmission of signals from Wernicke’s area to Broca’s area by way of the arcuate fasciculus
- Activation of skilled motor programs in Broca’s area for control of word formation
- Transmission from Broca’s area to the motor cortex to control the speech muscles
What is the cause of nerve deafness?
- Damage to the cochlear / auditory nerve
How is Weber’s test performed?
- Vibrating tuning fork is placed against in the middle of the patient’s forehead
- Normal result: The noise is heard in the middle or equally in both ears
- Conductive deafness: Sound heard louder on affected side
- Nerve deafness: Sound hear louder in normal ear
How is Rinne’s test performed?
- Vibrating tuning fork is placed on the mastoid process until it can no longer be heard, it is then moved over the external acoustic meatus
- Normal result: Air conduction is greater than bone conduction
- Conductive deafness: Rinne’s negative
What is otitis media?
- Middle ear infection
What are the symptoms of otitis media?
- Otalgia
- Conductive hearing loss (Rinne’s negative / In Weber’s test sound is loudest on affected side)
What is the treatment for otitis media?
- NSAIDs in acute phase
- If systemic features are present after 72 hours a systemic antibiotic (e.g. amoxicillin) should be given
What is secretory otitis media with effusion and how is it treated?
- Effusion in the middle ear
- Most commonly in children due to Eustachian tube dysfunction
- A grommet is inserted into tympanic membrane to ventilate middle ear (taking over role of Eustachian tube)
Identify one complication of otitis media
- Mastoiditis
- Tenderness and swelling over mastoid process
Why is a normal audiogram dome shaped?
- Normal frequency of voice is between 1000 and 4000 Hz
Why may be person be able to hear below 0 dB?
- It is a logarithmic scale
What is the vestibular apparatus?
- Sensory organ for detecting equilibrium
What does the static labyrinth detect?
- Orientation of the head in relation to the pull of gravity
What does the kinetic labyrinth detect?
- Information about acceleration and deceleration of the head
What is the static labyrinth composed of?
- Utricle superiorly and saccule inferiorly
- And their maculae
What is the role of the static labyrinth?
- Controlled balance by increasing antigravity muscular tone on the side to which the head is tilted
How are the maculae arranged in the utricle and saccule?
- Horizontal in utricle
- Vertical in saccule
Describe the structure of a macula
- Columnar supporting cells invested by hair cells to which vestibular nerve is applied
- Free surface of hair cell possesses 100 stereocilia with a single kinocilium
- Stereocilia are embedded a gelatinous matrix consisting of otoconia
What are otoconia and what is their function?
- Calcium carbonate crystals
- That exert gravitational drag on the hair cells
How does movement of the head cause an action potential in the vestibular nerve?
- Movement of otoliths pulls hair cells towards kinocilium
- Opening of cationic channel allows for entry of positive ions from endolymphatic fluid
- Causing receptor membrane depolarisation and an action potential in the vestibular nerve
How does the vestibular system mediate compensate antigravity movements of the head?
- Lateral vestibulospinal tract
- Which descends in the anterior funiculus
- And synapses with extensor antigravity muscles
What is the role of the kinetic labyrinth
- Keep the gaze on target during angular acceleration of the head
What is the kinetic labyrinth composed of?
- Anterior, posterior and lateral semicircular ducts
- Each of which possess a dilated end known as the ampulla
- Ampulla contains a cristae
Describe the structure of a cristae
- Columnar supporting cells invested by hair cells to which vestibular nerve is applied
- Free surface of hair cell possesses 100 stereocilia with a single kinocilium
- Stereocilia are embedded a gelatinous projection called the cupula
When the head moves, what happens to the endolymphatic fluid in the semicircular canals?
- It retains its original position
- Since it is not attached to the skull
When the head moves, what happens to the cupula in the semicircular canals? What is the effect
- It moves and pushes against the stationary endolymphatic fluid
- Which bends the stereocilia in the direction of the kinocilium, opens cation channels and causes an action potential in the vestibular nerve
The vestibular nuclei has connections with which region of the cerebellum?
- Floculonodular lobes
Briefly describe the movement of the eyes in the vestibulo-ocular reflex
- Results in compensatory eye movement that is equal but opposite to the movement of the head
From the vestibular nucleus, identify the signals involved in the vestibulo-ocular reflex
- Via medial longitudinal fasciculus
- To ipsilateral oculomotor nuclei supplying medial rectus
- And contralateral abducens nuclei supplying lateral rectus
What is nystagmus?
- Tremor of the eyeballs when eyeballs are fixated on a lateral point
How can nystagmus be elicited?
- Syringing external auditory meatus with hot water
- Which produces convection currents in endolymph in the warm cupula
- Resulting in a slow drift of eyes away from stimulated side
- Followed by a rapid recovery phase, repeated several times per second
Which tuning fork is used when performing Weber’s / Rinne’s test?
- 512 Hz
Which tuning fork is used when testing vibration sensation?
- 128 Hz
What is a phoneme? How many phonemes does the word hat have?
- Smallest unit of speech
- The sounds produced by letters
- 3 ‘h’ ‘a’ ‘t’
What is universal adaptivity and when is it lost?
- Ability to learn which phoneme is relevant to your own language
- Ability is lost after the first year
Between which ages does the critical period of language development occur?
- 4-12
Outline developmental milestone of speech
- Age 1: Begin speaking, map concepts onto words
- Age 1-2: Talk about people, animals, body parts and household items
- Age 1.5-2.5: Acquisition of phrases and sentences (syntax)
Outline three different theories of language development
- Skinner: Influence of environment on language development
- Piaget: Thought comes before language
- Vygotsky: Social support from adults enables a child to advance to the next level of language development
Identify two reasons why hearing loss in children can result in social isolation
- Delayed social development due to delayed language acquisition
- Inability to pick up auditory cues can result in them become irritable
Identify two social impacts of hearing loss
- Less fluid conversation
- Problematic interaction in noisy places
- Isolation
- Intimacy issues
Identify two psychological impacts of hearing loss
- Anger + frustration
- Low confidence
- Difficulty concentrating
- Embarrassment
What is the Noise at Work act?
- Employers are required to take precautions for the safety of employees hearing
Under which Act do individuals with hearing loss have additional rights in the workplace?
- Disability Discrimination Act
Identify four pieces of specialist equipment at home that can aid those with hearing loss
- Extra-loud doorbells
- Alarms that use vibration or light
- Television with subtitles
- Phones that allow for texting
According to Piaget’s theory of cognitive development, what is meant by schema?
- Basic building block of intelligent behaviour
- Relating to one aspect of world
- Including objects, actions and abstract concepts
According to Piaget’s theory of cognitive development, what is meant by assimilation?
- The way in which children use existing schemas to deal with new situations or objects
According to Piaget’s theory of cognitive development, what is meant by accommodation?
- A situation in which an existing schema does not work
- So a new one must be developed
According to Piaget’s theory of cognitive development, what is meant by equilibration?
- Situation in which a child’s schemas can deal with most new information through assimilation
- Driving force behind learning
Identify Piaget’s four stages of cognitive development, when they occur, and a brief overview of what each stage involves
- Sensorimotor, 0-2, trial and error, experimentation
- Preoperational, 2-7, imagination and memory
- Concrete operational, 7-12, logical thought
- Formal operation, 12-18, abstract thought
