S3C4 (2.0) Flashcards
What is the role of the vestibular system?
Balance and spatial orientation
What does the vestibular system consist of?
Otolith organs - uttricle and saccule
Semicircular canal
What is the role of the otolith organs?
Detect changes in gravity (e.g., head position) and generate electric impulses transmitted by the vestibular nerve
What are maculae?
Thickenings in the wall of the utricle and saccule, which consist of supporting cells, vestibular hair cells, an otolithic membrane, and otoliths (particles of calcium carbonate)
What does the utricle sense?
Senses motions in the horizontal plane
What does the saccule sense?
Sense motions in the sagittal plane (vertical)
What does the semicircular sense?
Sense rotary movements at their ampullas
Where do the hair cells of the vestibular organ synapse?
Each hair cell makes an excitatory synapse with the end of a sensatory axon from the vestibular nerve, branch of the vestibulocochlear nerve (CN VIII)
Where are the cell bodies of the vestibular nerve axons?
Scarpas ganglion
What are the membranous sacs withing the bone (vestibular system) filled with?
Endolymph - collectively called the membranous labyrinth
What is the chemical composition of endolymph?
High in K+ and low in Na+.
What is between the bony walls (the osseous labyrinth) and the membranous labyrinth?
Perilymph
What is the chemical composition of perilymph?
Low in K+ and high in Na
What is the role of the tight junctions that seal the apical surfaces of the vestibular hair cells?
Ensuring that endolymph selectively bathes the hair cell bundle while remaining separate from the perilymph surrounding the basal portion of the hair cell
What does movements of the stereocilia towards the kinocilium cause?
The vestibular organs opens mechanically gated transduction channels located at the tips of the stereocilia.
This causes depolarisation of the hair cell, causing neurotransmitter release onto (and excitation of) the vestibular nerve fibres.
What does the biphasic nature of the receptor potential mean?
Some transduction channels are open in the absence of stimulation, with the result that hair cells tonically release neurotransmitter, thereby generating considerable spontaneous activity in vestibular nerve fibres
What is the role of the stroila?
Divide the hair cells into two populations with opposing polarities in the utricle and saccule
What is the otolithic membrane?
A fibrous structure in which crystals of calcium carbonate called otoliths are embedded
What happens when the head tilts?
Gravity causes the membrane to shift relative to the sensory epithelium.
The shearing motion between the otolithic membrane and macula displaces the hair bundles
This displacement of the hair bundles generates a receptor potential in the hair cells.
Where are the hair bundles in the otolith organs?
Embedded in the lower, gelatinous surface of the membrane.
What signalling pattern from the otoliths would indicate an absolute head position?
Sustained
What signalling pattern from the otoliths would indicate an linear acceleration of the head?
Transient
What happens when the head turns in the plane of one of the semicircular canals?
The inertia of the endolymph produces a force across the cupula, distending it away from the direction of head movement and causing a displacement of the hair bundles within the crista.
What are the consonant features?
Manner
Voicing
Place
What is manner?
Manner - the way sound is said
fricatives (hissing noise)
Plosives (exploding from the lips e.g. pp)
Nasals (use the nose to produce resonance e.g. Mm)
What is voicing?
(b-p, d-t, g-k, z-s)
Duration (voice onset time)
Intensity
What is place? (speech)
(b-d-g, p-t-k)
Frequency
Intensity
What are formants?
chunks of energy clustered in certain frequency areas. In the case of vowels, the first two formants combined create a characteristic vowel which enables differentiation between subtly different sounds
What does successful language require?
Attention Speech perception Speech production Language: vocab, grammar, syntax Auditory memory Auditory feedback Social skills and pragmatics
What language skills can you expect at 2 months old?
Pre-verbal
Crying
Gestures
Coos and gurgles
What language skills can you expect at 6-10 months old?
Babbling
Can distinguish sounds and reproduce them
Communicates by sounds and intonations
Able to express pleasure and displeasure.
What language skills can you expect at 6-12 months old?
Begin by detecting very small differences between speech sounds - phonemes
As they get older they learn to ignore other non specific sounds
contrast different vowel phonemes
recognise consonants
What language skills can you expect at 1 year old?
On word stage - morphemes Understand 50 words say 5 one word to describe actions semantics develops before word
What language skills can you expect at 18 months old?
Two word phrases 20-50 words Naming Demanding Questioning
What language skills can you expect at 2.5 years old?
Simple sentences Lacks tenses Errors in syntax Recognition of rhyme and intonation 200-300 words
What language skills can you expect between 2.5-5 years old?
improvements in phonemes
Development of pronunciation - articulation
What language skills can you expect between 6-10 years old?
Master syllable stress to distinguish between similar words
What did Piaget argue?
Thought comes before language.
What did Skinner think was important for language development?
Environment
What did Vgotsky say can enable a child to advance?
Social support from adults and especially from more competent peers
What % of profoundly deaf children are born into hearing families?
90%
What is the impact of a deaf child being born into hearing families?
Delayed Theory of Mind development
What was the bat-Chava meta analysis?
Deaf children of deaf parents had higher self esteem than deaf children of hearing parents
Self-esteem higher among deaf people using sign language
What are the 4 developmental pathways? (Glickman and Harvey)
Culturally hearing
Culturally marginal
Culturally Deaf
Bicultural
What happens at the level of the medulla? (cochlear)
The axons innervate the dorsal cochlear nucleus and ventral cochlear nucleus ipsilateral to the cochlea where the axons originated.
Where do the axons from the ventral cochlear nucleus project?
The superior olive (superior olivary nucleus) on both sides of the brain stem.
Where do the axons of the olivary neurons ascend?
Ascend in the lateral lemniscus and innervate the inferior colliculus of the midbrain.
Where do all ascending auditory pathways converge?
Inferior colliculus
Where do the neurons in the inferior colliculus send out axons?
The medial geniculate nucleus (MGN) of the thalamus, which in turn projects to auditory cortex
Where do the cochlear nuclei receive input from?
The ear on the ipsilateral side
What does the anterior inferior cerebellar artery supply?
The cochlear nuclei
What is the monaural pathway?
From the cochlear nucleus bypasses the superior olive and terminates in the nuclei of the lateral lemniscus on the contralateral side of the brainstem.
These particular pathways respond to sound arriving at one ear only
Where is the MGN?
Thalamus
What are the layers of the auditory cortex?
6 layers:
Layer I contains few cell bodies
Layers II and III contain mostly small pyramidal cells
Layer IV, where the medial geniculate axons terminate, is composed of densely packed granule cells.
Layers V and VI contain mostly pyramidal cells that tend to be larger
Where is the primary auditory cortex?
Superior temporal gyrus in the temporal lobe and receives point-to-point input from the ventral division of the MGN
What is the role of the vestibulo-ocular reflex?
A mechanism for producing eye movements that counter head movements, thus permitting the gaze to remain fixed on a particular point.
These eye movements compensate for head movements to produce a stable image on the retina.
What is the role of the vestibulo-cervical reflex?
Postural adjustments of the head
What is the role of the vestibulo-spinal reflex?
Postural adjustments of the body
What is otitis media?
An 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 in the nasopharynx
When does acute otitis media occur?
When pathogens from the nasopharynx are introduced into the inflammatory fluid collected in the middle ear
What are the parts of the outer ear?
Auricle
EAM
Tympanic membrane
What is the function of the pinna?
Collect sound waves, important for directional hearing
What is the pinna made of?
Elastic cartilage
What is the EAM made of?
Outer third cartilage
Inner two thirds bone
What is the EAM lined with?
Thin keratinised stratified squamous epithelium
What is the function of the EAM?
Transmission of sound waves to tympanic membrane
What is the tympanic membrane?
Thin cone shaped membrane
Cutaneous outer layer, fibrous middle and mucous inner layer
What is the umbo?
The point where ossicles attach to the tympanic membrane
What is the cone of light?
A cone-shaped light reflection of the otoscope light in the anterior inferior quadrant
What is the function of the tympanic membrane?
Sound waves cause vibration of the tympanic membrane, which in turn transmits these vibrations to the ossicles of the middle ear
What does the middle ear consist of?
Tympanic cavity, mastoid process and eustachian tube
What is the tympanic cavity?
Air filled space located within the petrous portion of temporal bone
Contains ossicles, muscles and nerves
Connected to nasopharyngeal cavity via the eustachian tube
What is the oval window?
An opening at the base of the cochlea through which sound waves are transmitted to the inner ear
Covered by the footplate of the stapes
What is the round window?
A membrane-covered opening in the middle ear that lies below the stapes-covered oval window.
Vibrations of the footplate of the stapes are transmitted to the round window through the perilymph, which causes it to vibrate in the opposite phase of the oval window.
How does the middle ear?
Focusing the force impinging on the relatively large-diameter tympanic membrane on to the much smaller-diameter oval window.
The mechanical advantage gained by the lever action of the three ossicles which connect the tympanic membrane to the oval window.
What is the difference in pressure exerted on the oval window compared to the tympanic membrane?
The pressure exerted on the oval window is about 20 times greater
What are the ossicles?
Malleus - inserts laterally into the tympanic membrane
Incus - connects to malleus laterally and stapes medially
Stapes - inserts medially into the membrane of the oval window
What is the Eustachian tube?
Connects the middle ear cavity with the nasopharynx
Control the pressure within the middle ear and allows the pressure to be equalised on both sides of the tympanic membrane
Opens when chewing, swallowing or yawning
What is the origin of the Tensor tympani muscle?
Cartilaginous and bony margins of the eustachian tube
What is the insertion of the Tensor tympani muscle?
Handle of the malleus
What is the action of the Tensor tympani muscle?
Contraction of the muscle pulls the malleus medially
This tenses the tympanic membrane and damps vibration in the ear ossicles, resulting in a reduction of the perceived amplitude of sound
What is the innervation of the Tensor tympani muscle?
Medial pterygoid nerve, branch of mandibular (V3)
What is the origin of the stapedius muscle?
Cartilaginous and bony margins of eustachian tube
What is the insertion of the stapedius muscle?
Neck of stapes
What is the action of the stapedius muscle?
Contraction of the muscle pulls the neck of the stapes laterally, thereby damping the vibrations of the stapes and allowing it to control the amplitude of sound waves being transmitted to the inner ear
What is the innervation of the stapedius muscle?
The nerve to stapedius, branch of the facial nerve
What is the mastoid process?
Process of temporal bone behind the ear
Where is the inner ear situated?
The petrous part of temporal bone
What are the parts of the inner ear?
Labyrinth
Cochlea
Vestibular system
What is the labyrinth divided into?
Osseous part
Membranous part
What is the osseous labyrinth lined with?
Periosteum
What is the osseous labyrinth?
The bony wall of the inner ear in the temporal bone
Contains the vestibule, 3 semi-circular canals, and cochlea
Where is the membranous labyrinth?
Lodged within the osseous labyrinth in perilymph
What is the membranous labyrinth filled with?
Endolymph
Where is the scala vestibuli?
Filled with perilymph; begins at oval window; connected with tympanic duct at helicotrema
What is the role of the scala media?
filled with endolymph; To control spiral organ of Corti and auditory hair cells
Where is the scala tympani?
Filled with perilymph; ends at round window
What are the layers of the cochlea?
Bone Vestibular duct Reissner membrane Cochlear duct Basilar membrane: thin at the basal end and wide at the apical end; supports organ of corti Tympanic membrane Bone
What is the function of the cochlea?
Transformation of the airborne vibrations into auditory neural signals
What is the role of the stria vascularis?
Produces potassium-rich endolymph for the scala media, which is essential for the endocochlear potential
What is the auditory pathway?
Auditory neural signals detected by the hair cells of the organ of Corti
Bipolar neurons of the cochlear or spiral ganglion via the cochlear part of the vestibulocochlear nerve
Ventral and dorsal nuclei (in the medullopontine junction)
Superior olivary nucleus (from the ventral nucleus to the trapezoid body)
Bilaterally to the lateral lemniscus
Inferior colliculus
Medial geniculate body
Auditory radiations
Primary auditory cortex (superior temporal gyrus in the temporal lobe) and amygdala
Auditory association cortex
What is the vestibular pathway?
Hair cells of the semicircular canals, macule, and saccule (otolith organs)
Bipolar neurons of the vestibular ganglion
Vestibular nerve
Vestibular nuclei: inferior, medial, superior, and lateral (in the pons and medulla)
Cerebellum (flocculonodular lobe), nuclei of CN III, IV, VI (for the vestibulo-ocular reflex), reticular formation (aids in body positioning), spinal cord, and the thalamus
What are the structural properties of the basilar membrane that determines its response to sound?
The membrane is wider at the apex than at the base by a factor of about 5.
The stiffness of the membrane decreases from the base to apex, the base being about 100 times stiffer.
What happens when sound pushes the footplate of the stapes?
perilymph is displaced within the scala vestibuli, and endolymph is displaced within the scala media
makes the basilar membrane bend near its base
What does the organ of corti consist of?
Hair cells (auditory receptors), the rods of Corti, and various supporting cells.
What is the neurotransmitter for hair cells in Organ of corti?
Glutamate
Where are the hair cells in organ of corti?
Sandwiched between the basilar membrane and the reticular lamina.
What depolarises hair cells?
Displacement of the hair bundle parallel to this plane toward the tallest stereocilia
What hyperpolarises hair cells?
Movements parallel to this plane toward the shortest stereocilia
What cation channel is on the tips of the stereocilia?
TRPA1
What happens to TRPA1 when the stereocilia bend?
TRPA1 channels open, causing an influx of Na+ and K+ ions. This generates changes in the hair cell receptor potential
What is the tip link?
An elastic filament linking TRPA1 channels to the wall of the adjacent cilium.
What happens when the stereocilia are straight?
the tension on the tip link holds the channel in a partially opened state, allowing a small leak of K+ from the endolymph into the hair cell.
What is the resting potential of a hair cell?
-45 to -60 mV
What is the endocochlear potential?
The compartment containing endolymph is about 80 mV more positive than the perilymph compartment
How does Ca2+ get into hair cells?
K+ entry via the transduction channels depolarizes the hair cell, opening voltage-gated Ca2+ and K+ channels located in the membrane of the hair cell soma.
What are the types of hair cells?
Inner and Outer
What % of auditory nerve fibres arise from inner hair cells?
95%
How many spiral ganglions are connected to each inner hair cell?
10
How many inner hair cells are connected to each spiral ganglion?
1
Where are the terminations of the outer hair cells from?
Almost all from efferent axons that arise from cells in the superior olivary complex
What is the role of outer hair cells?
Cochlear amplification
act like tiny motors that amplify the movement of the basilar membrane during low-intensity sound stimuli
How does cochlear amplification occur?
Occurs as a result of motor proteins present in the membranes of the outer cells.
Motor proteins can change the length of outer hair cells.
Outer hair cells respond to sound with both a receptor potential and a change in length.
What motor protein is involved in cochlear amplification>
Prestin
