Auditory System Flashcards
What is sound?
The displacement of air particles following a sinusoidal pattern of compression and rarefacation
What are the components of the auditory system?
Outer Ear- air
Middle Ear- air
Inner Ear- fluid
Central Auditory Pathways
What does the outer ear consist of?
Pinna
Ear Canal
Tympanic membrane
What is the pinna made up of?
Cartilage
What is the pinna formed from?
Pharyngeal arches 1 & 2 ( 6x Hillocks of His)
What weeks does the pinna form between in utero?
10th to 18th week
What is the function of the Pinna?
Directs soundwaves towards ear canal
What is the ear canal made from?
1/3 cartilage & 2/3 bone
What bones make up the middle ear?
Malleus
Incus
Stapes
What muscles make up the middle ear?
Tensor Tympani
Stapedius
What tube is in the middle ear?
Eustachian Tube
What is the role of the middle ear?
Acoustic impedance match between air and fluid- filled inner ear
What is the role of the muscles in the middle ear?
Protection of the inner ear from acoustic trauma
Stiffens the ossciular chain
Stapedius stimulated acoustically
What is the role of the eustachian tube?
Ventillation of the middle ear space
Drainage of secretions
What is the vestibulocochlear apparatus?
A set of fluid filled sacs, encased in bone
What is the cochlear responsible for?
Hearing
What is the labyrinth responsible for?
Balance
What is the vestibulocochlear apparatus innervated by?
Vestibulocochlear nerve
What are the 2 openings of the cochlea?
Round window
Oval window
What are the 3 compartments of the cochlea?
Scala Tympani
Scala Media
Scala Vestibuli
What are the 2 cochlear fluids?
Endolymph
Perilymph
What is the endolymph made up of?
High K+
What is the perilymph made up of?
Like ECF and CSF
Na+ rich
How are the gradients of the cochlear fluids maintained?
Na, K-ATPase & NKCC1 CIC-K chlorine channels
What can ion channel abnormalities lead to?
Deafness
What does displacement of the basilar membrane cause?
Causes movement of specialized mechanical transducing cells
What is the function of inner hair cells?
Mechanical transduction
What is the function of outer hair cells?
Fine tuning
How is frequency (pitch) encoded?
Encoded in nerves by location along the basilar membrane
How is intensity (loudness) encoded?
Encoded in nerves by numbers responding and by firing rate
How is sound transduction encoded?
Inner Hair Cells (and OHCs)
How is amplification encoded?
Outer Hair Cells
What are the types of hearing loss?
Conductive
Sensorineural
What is conductive hearing loss?
Defective outer/middle ear
What is sensorineural hearing loss?
Defective Inner Ear
