Peripheral auditory stimulus & brain activity

Peripheral Auditory Stimulus & Peripheral Auditory Stimulus & Brain ActivityBrain Activity

Peripheral Auditory PathPeripheral Auditory Path

This auditory path to the This auditory path to the brain includes:brain includes:

1.1. Outer ear stimulusOuter ear stimulus

2.2. Middle ear stimulusMiddle ear stimulus

3.3. Inner ear stimulusInner ear stimulus



The stimulus “modifications” The stimulus “modifications” received from each of these received from each of these peripheral areas are peripheral areas are cumulative in nature.cumulative in nature.

Each modify the acoustic Each modify the acoustic signal.signal.



Almost all of the peripheral Almost all of the peripheral auditory mechanism is auditory mechanism is located in the located in the temporal bone.temporal bone.



There is a temporal bone on There is a temporal bone on for each ear. It covers the for each ear. It covers the temporal lobe area of the temporal lobe area of the brain.brain.


Outer Ear (Pinna) contributionOuter Ear (Pinna) contribution

It “collects” acoustic It “collects” acoustic information and creates information and creates resonances of that acoustic resonances of that acoustic information, which are further information, which are further modified in the external modified in the external auditory meatus.auditory meatus.


External Auditory Meatus (ear canal) External Auditory Meatus (ear canal) contributioncontribution

The resonances collected by the The resonances collected by the pinna result in a characteristic pinna result in a characteristic fundamental resonant peak for fundamental resonant peak for each ear (usually around each ear (usually around 2700Hz).2700Hz).


Tympanic membrane (eardrum) Tympanic membrane (eardrum) contributioncontribution

The TM has a surface area seventeen The TM has a surface area seventeen times larger than the foot plate of the times larger than the foot plate of the stapes at the round window. stapes at the round window.

This creates an areal ratio, which This creates an areal ratio, which when coupled with the movement of when coupled with the movement of the middle ear bones, further the middle ear bones, further modifies the received acoustic signal. modifies the received acoustic signal.


The Ossicles (middle ear bones) The Ossicles (middle ear bones) contributioncontribution

This is the area where the sound This is the area where the sound becomes “mechanically” amplified becomes “mechanically” amplified with the Class II lever function.with the Class II lever function.


The Ossicles (middle ear bones) The Ossicles (middle ear bones) contributioncontribution

This is also where the stapedial and This is also where the stapedial and tensor tympani muscles are modified tensor tympani muscles are modified by efferent information from the by efferent information from the brain.brain.

It is the first location in the acoustic It is the first location in the acoustic path which becomes modified with path which becomes modified with brain activity.brain activity.


The Inner Ear contributionsThe Inner Ear contributions

This is where the acoustic This is where the acoustic and mechanical modifications and mechanical modifications are “transduced” into fluid are “transduced” into fluid movement (hydraulic) movement (hydraulic) energy.energy.


The Inner Ear contributionThe Inner Ear contribution

This hydraulic movement of This hydraulic movement of perilymph fluid creates perilymph fluid creates undulations of the basilar undulations of the basilar membrane. membrane.

The Organ of Corti which contains The Organ of Corti which contains the inner and outer hair cells rests the inner and outer hair cells rests upon this membrane.upon this membrane.



As the outer hair cells wave As the outer hair cells wave around, they “sweep” against around, they “sweep” against the tectorial membrane. the tectorial membrane.

This hair cell movement This hair cell movement creates the sixty decibel creates the sixty decibel cochlear compressor (2.5:1) cochlear compressor (2.5:1) amplifier.amplifier.



This is the next location This is the next location where the brain sends where the brain sends efferent information to efferent information to modify the performance of modify the performance of the the cochlear amplifiercochlear amplifier..



This activity by the hair cells This activity by the hair cells within the Organ of Corti within the Organ of Corti synapse (innervate) the synapse (innervate) the eighth cranial nerve eighth cranial nerve (auditory nerve).(auditory nerve).



The auditory (VIIIth) nerve The auditory (VIIIth) nerve stimulation information stimulation information begins the afferent path to begins the afferent path to the cochlear nucleus of each the cochlear nucleus of each ear.ear.


Healthy Brain contributionHealthy Brain contribution

With healthy brain performance, With healthy brain performance, the afferent pathways of the the afferent pathways of the auditory system will now create auditory system will now create reactionary activity and reactionary activity and contribute to good health for all contribute to good health for all systems controlled by the brain.systems controlled by the brain.

Health & Medicine

Peripheral auditory stimulus & brain activity