COGS 17 Lecture Notes - Lecture 9: Crista Ampullaris, Semicircular Canals, Topological Map
19 May 2018
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Continuation of audition……..
Topological map:
High frequency sound moves from Inferior colliculus (midbbrain) to medial
geniculate Nucleus (thalamus) to A1 (medial-temporal lobe)
A1→ frequency and amplitude maps
A1 (strongest response to one unchanging frequency)->A2 (strongest
response to changing frequencies)->A3->A4
Highest auditory cortex is the Wernicke’s Area specialized for comprehending
speech (does not detect frequency)
Nuclei of the thalamus:
● LGN, MGN, VPN, DMN, VLN, MDN
Vestibular system
3 Semicircular canals (when your head rotates, they still keeps balance)
● Each canal is filled with K+ called endolymph
● Hair cells are located in the ampullae at the base of the canals
● Inside the ampullae there is crista ampullaris, with hair cells
embedded in the cupula (gelatonous structure)
● Whenever you move or rotate, the cilia of hair cells embedded in
cupula are bent by the flow of endolymph in ampulla
● At the start of rotation, fluid lags behind (delays a while before keeping
up)
● At the end of rotation, fluid overshoots (even after you stop moving,
the fluid still moves for a while)
Vestibular hair cells functions the same way as the auditory hair cells, as far
as firing graded potential neurotransmitters. But in vestibular hair cells, even if you
are still and there is no rotation, there is a spontaneous firing (meaning hair cells
releases neurotransmitters)
Otolith organs= head tilt:
● Utricle and saccule are the otolith organs
● Macula is made of utricle and saccule
● Otoliths are small calcium chloride crystals that sit on the gelatinous
materials of hair cells
● If you tilt your head, gravity pulls the otolith toward the direction your head
is tilted and cilia bends either more or less depending on your position
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Document Summary
High frequency sound moves from inferior colliculus (midbbrain) to medial geniculate nucleus (thalamus) to a1 (medial-temporal lobe) A1 (strongest response to one unchanging frequency)->a2 (strongest response to changing frequencies)->a3->a4. Highest auditory cortex is the wernicke"s area specialized for comprehending speech (does not detect frequency) 3 semicircular canals (when your head rotates, they still keeps balance) Each canal is filled with k+ called endolymph. Hair cells are located in the ampullae at the base of the canals. Inside the ampullae there is crista ampullaris, with hair cells embedded in the cupula (gelatonous structure) Whenever you move or rotate, the cilia of hair cells embedded in cupula are bent by the flow of endolymph in ampulla. At the start of rotation, fluid lags behind (delays a while before keeping up) At the end of rotation, fluid overshoots (even after you stop moving, the fluid still moves for a while)
