Flashcards in Case 4 Deck (17):
What are the channels on the stereocilia on the hair cells called?
mechanically gated transduction channels (TPR1 channels)
When K+ ions enter the stereolcilia, the resulting depolarisation quickly spreads along the plasma membrane, what does this lead to?
Opens voltage-gated Ca2+ channels?
What does the entrance of Ca2+ into the stereocilia cause?
Triggers exocytosis of synaptic vesicles containing glutamate.
What and where are spiral ganglion located?
Cell bodies of the choclear nerve afferents, located in the modiolus.
What happens to their peripheral and central processes?
Peripheral processes (dendrites) synapse with the hair cell, central processes (axons) make up the choclear division of the VIIIth CN.
Where do the primary afferents of the vesibular system synapes?
One of four nuclei in the rostral medulla and caudal pins (medial, lateral, inferior and superior).
What are central auditory dysfunctions and what do they cause?
Defects in auditory brainstem or cortex, do not produce significant hearing loss, rather cause difficulties locating or discriminating sound.
What is an audiometry?
Produces a puretone sound at different amplitudes over a range of frequencies. Can identify frequencies lost.
What is a common cause of low-frequency lose?
Middle ear disease
What is a common cause of high frequency loss?
Choclear nerve damage.
How does dysfunction of the eustachian tube lead to ottitis media?
Gas volume is trapped in the middle ear, parts are slowly absorbed into surrounding tissue leading to a negative pressure in the ear. This eventually leads to fluid from the surrounding ear being sucked into the typanic cavity, causing middle-ear effusion.
The fluid accumualted in the middle ear may become infected, what are the common pathogens?
Streptococcus pneumonia is most common, H. influenza and moraxella catarrhalis.
What is the difference between acute and chronic otitis media?
Chronic occurs when there is a perforation in the tympanic membrane and an active infection.
What are the three categories babies communication falls into before they are capable of speech?
Rejection, request, comment (pointing out and object accompanied by some vocalisation)
Where are sounds processed as meaingful words?
What happens in Broca's area?
Words are converted to code for muscular movement of speech.