Auditory System Flashcards
What is the importance of sound?
Allows for communication
Important for emotion
Helps us to map out the world
Helps with survival
How is sound information relayed from the ear to the brain? And how are complex sounds processed?
Highly specialised structures. And the cochlear.
Complex sounds which travel into the ear create one directional movements in the ear drums. These vibrations allow us to process and recognise different sounds and pinpoint where sounds come from.
What features of sound need to be encoded?
Frequency and intensity
The frequency is related to pitch and is in Hertz
- this is detected by the cochlear mechanicals and hair cells
Sound intensity:
Is loudness - measured in decibels
We hear a huge range of sound intensity
This detection is achieved via the firing of many nerve fibres
Note the rapid onset of sound is also encoded for to create a map of the auditory space.
What is important for the ears?
It has to remain sensitive for long periods of time and its important they don’t fatigue.
How is sound transmitted in the ear?
The cochlea has sensory hair cells and nerve fibres
These transmit sound to the brain as neuronal signals.
What are the three chambers of the cochlear? What is located at the bottom of the scala media? What does the organ of corti receive innervation from?
The scala vestibuli, scala tympani and scala media
At the bottom of the scala media is the organ of corti - this is the sensory organ of the cochlear that contains the sensory hair cells.
The organ of corti receives innervation from the auditory nerve which spirals up towards the brain.
Where is the scala media in reference to the scala tympani and the scala vestibuli?
Its in the middle of the other two. Just remember that.
The tympani is above it
and the VESTIBULI is below it.
What is perilymph? Where is it found?
Perilymph is a fluid
Its fluid is similar to extracellular fluid
It has a LOW amount of potassium ions (remember the extracellular fluid has less potassium ions than the inside of the cell would, than the intracellular) (5mM)
It has a normal levels of calcium (1.3mM)
Where is it found?
In the scala tympani and scala vestibuli
What is endolymph ? and where is it found?
This is similar to intracellular solutions
It has a high concentration of potassium ions (150mM)
and has a low amount of calcium ions (20mM)
Where is it found?
Found in the scala media.
What is the membrane potential (endocochlear potential) of the scala media? And what is this caused by?
The membrane potential is +80mv
This is due to the high concentration of potassium 150mM in the endolymph of the scala media.
What are the two hair cells in the cochlear?
Theses are the inner and outer hair cells
The inner hair cells are sensory organs in the cochlear
The outer hairs cells are the sound amplifiers in the cochlear
Where is the organ of corti found? And the nerves that innervate it?
Bottom of scala MEDIA and innervated by neurones on the basilar membrane
What determines animals hearing frequency ranges?
This is determined by the size of the animal
The need to communicate over long distances
The need to hunt and for survival
How do bats and dolphins have echolocation?
Their hair cells in the base respond to very high frequency sounds.
What is preserved along the auditory pathway?
The tonotopic organisation