~Chapter 11 - Lecture Section 11.2 Flashcards
What are the parts of the Outer Ear?
The Pinnae, the Auditory Canal, and the Tympanic Membrane (eardrum)
What are the parts of the Middle Ear?
The Ossicles, the Oval Window, and the Middle Ear Muscles
What are the parts of the Inner Ear?
The Cochlea
Which part of the Ear holds up our glasses?
The Pinnae
The shape of the ___ is important for sound localization
Pinnae
Does the Pinnae play a role in transduction?
Not a large one, no
True or False: The length of the Auditory Canal is important
True
The sound waves that are reflected off of your ___ create ___ interference with incoming waves, such that sound in the range of ___Hz is amplified.
eardrum (the Tympanic Membrane) // constructive // 2,000-5,000
Where is the Tympanic Membrane (Eardrum) located?
At the very end of the Auditory Canal
Which part of the Ear serves as the border between the Outer and Middle Ear?
The Tympanic Membrane (Eardrum)
The Middle Ear consists of an ___ and ___ structures.
air-filled chamber // amplification
What are the Ossicles?
Malleus (Hammer), Incus (Anvil), Stapes (Stirrup)
Where are the smallest bones in the human body located?
In the Middle Ear. They are the Malleus (Hammer), Incus (Anvil), and Stapes (Stirrup)
The ___ connect the Tympanic Membrane to the ___.
Ossicles // Cochlea
How were the Ossicles named?
They are named after their shape
What is the job of the Ossicles?
Their job is to amplify sound-waves
The Ossicles are associated with the ___.
Middle Ear Muscles
Where are the smallest skeletal muscles in the human body located?
In the Middle Ear, they are the Middle Ear Muscles
What is the job of the Middle Ear Muscles?
Their job is to dampen vibration at the Ossicles at high intensities
As sound-waves are pressing onto the Tympanic Membrane, there is vibration that is transmitted through the Ossicles, and it pushes onto the ___ of the Cochlea.
Oval Window
The ___ is filled with fluid, so it cannot compress, and so whenever the ___ pushes in on the ___, the ___ pops out.
Cochlea // Stapes // Oval Window // Round Window
There are ___ ways that the Ossicles cause physical amplification in the Middle Ear
2
What is the first way that the Ossicles cause physical amplification in the Middle Ear?
The Tympanic Membrane has a much larger surface area than the surface area of the Stapes foot plate, therefore the Ossicles concentrate the vibration onto a much smaller surface area which increases the sound-pressure level by a factor of 17.
What is the second way that the Ossicles cause physical amplification in the Middle Ear?
By acting as levers, a bit like a teeter totter, and this increases vibration by a factor of 1.3P
Why is Physical amplification of sound by the Middle Ear required?
Because pressure changes in the air (Outer and Middle ear) are transmitted poorly to liquid (the Cochlear fluid) and so it requires amplification in order to make those sound vibrations large enough to produce Transduction.
Why do some fish not have Outer and Middle Ear structures?
Because they do not need to amplify sounds as greatly since water and Cochlear fluid have similar densities, both the Outer and Inner areas are both fluid-filled.
When you listen to sound underwater, that dampening is what’s being overcome by the amplification in the ___.
Middle Ear
What are the physical characteristics of the Cochlea?
In its natural state, the Cochlea is a spiral-shape.
The Cochlea is about 2mm x 35mm
Pressure changes produced by the movement of the Stapes creates vibrations that are transmitted to the fluid, and so the ___ that are impinging on the Tympanic Membrane through the amplification by the Ossicles, and this spiral-nature of the Cochlea set up ___ in the ___.
longitudinal waves // transverse waves // Basilar Membrane
Is the Cochlea an air-filled or fluid-filled structure?
Fluid-filled structure
The Cochlea is split into two parts by the ___.
Cochlear Partition
What is the Scala Vestibuli?
The top part of the Cochlea
In the Scala Vestibuli, the top part, which is connected to the ___ and ___, extends from the ___ at the Cochlea’s Base to the Apex.
Stapes // Oval Window // Oval window
What is the Scala Tympani?
The bottom part of the Cochlea
The Scala Tympani is the part that extends from the Apex to the ___ at the Cochlea’s base
Round Window
Where is the Basilar Membrane located?
Within the Scala Tympani
At the Apex of the Cochlea, there is an opening where the fluid pressure that increases at the ___, is transmitted through to the ___.
Scala Vestibuli // Scala Tympani
Where is the Organ of Corti located?
The Organ of Corti is located in the Cochlea, and sits on the bottom of the Basilar Membrane in the Scala Media
What is the Scala Media?
The Scala Media is a fluid canal that sits in between the Vestibuli and Tympani
Where is the site of sound transduction into neural activity?
The Organ of Corti
The Organ of Corti consists of hair-cells, there is a ___ row of Inner hair cells and ___ row(s) of Outer hair cells. A gelatinous ___ sits and flops and touches all of the bristles on the hair cells.
single // 3 // Tectorial Membrane
The 3 Outer rows of Cilia/Hair cells are arranged in a ___ pattern.
Chevron
There are ___ Inner hair cells and ___ Outer hair cells
3,500 // 12,000
Hair cells are connected to fibers that leave the Cochlea as the ___.
Auditory Nerve
The Inner hair cells send ___ inputs such that each hair cell connects to ___ Auditory Nerve Fibres.
diverging // 8-30
Outer hair cells send ___ inputs to each Auditory Nerve Fiber, and each fibre is connected to many Outer hair cells.
converging
All the hair cells have Cilia, and when the Cillia ___, the transduction process starts.
bend
What is the transformation of longitudinal sound-waves into transverse waves of the Basilar Membrane?
When the Stapes vibrates, the Oval Window vibrates, this causes pressure changes in the Cochlear fluid.
What is the Transverse wave?
The Basilar Membrane vibrates at the same frequency as the Stapes, up and down
Depending on the direction the Cilia are deflected, it will produce either ___ or ___ in the hair cell.
Depolarization // Hyperpolarization
Depending on the direction the Cilia are deflected, it will produce either ___ or ___ in the hair cell.
Depolarization // Hyperpolarization
If the Cilia are deflected toward the long side, it produces ___.
Depolarization
If the Cilia are deflected toward the short side, it produces ___.
Hyperpolarization
Do hair cells fire action potentials?
No, the hair cells themselves do not fire action potentials
The hair cells themselves do not fire action potentials, but the ___ that they’re connected to will ___ their firing rate when the hair cells are Depolarized, and they will ___ their firing rate when the hair cells are Hyperpolarized.
Auditory Nerves // increase // decrease
Each hair cell has ___ extracellular environments.
2
What is the first extracellular environment of the hair cell?
On the top where the Cilia rest. In the Scala Media there is a fluid called Endolymph which has an extremely high K+ concentration (+80mV).
What separates the 2 extracellular environments of the hair cell?
Tight junctions referred to as the Reticular Lamina which seal off the top compartment from the rest of the cell
What is the second extracellular environment of the hair cell?
The fluid of the Paralymph is similar to Cerebral Spinal Fluid (CSF), it has lower K+ concentration (0mV).
Endolymph which has an extremely ___ K+ concentration of around ___.
high // +80mV
Paralymph is similar to ___, it has ___ K+ concentration of ___.
Cerebral Spinal Fluid (CSF) // lower // 0mV
What is one function of the very unusual structure of the two different extracellular environments of hair cells?
It is important for producing neural activity in the hair cells.
What is the resting potential of an Outer hair cell?
-70mV
What is the resting potential of an Inner hair cell?
-40mV
___ are the mechanism of Transduction.
Tip Links
How are Cilia connected to one another?
By Tip Links
What are Tip Links?
Strands/strings that link Cilia together
Tip Links pull on ___ that will open or close depending on the ___ of the Tip Links.
ion channels // tension
Tip Link is made of a protein called ___, and this ___ strand connects two hair cell ___ channels.
Cadherin23 // Cadherin23 // Mechanoelectrical Transduction (hcMET)
The ___ tension that is on the Tip Link, it will pull these hcMET channels open, and allow ions to flow.
more
What is the problem with hcMET?
The actual identity of what these hcMET are is debated
Some say it’s a TRPA1 channel, and some don’t assign it an identity at all.
-For our purposes, the hcMET is more of an agnostic, it’s talking about its function rather than its genetic origin.
The structure of these two channels that are linked by this strand create a ____.
mechanically gated ion channel
At rest, there is a ___ tension on the Tip Links, and hcMET gates are pulled ___, and it’s letting a little bit of that K+ from the ___ flow in.
medium // partially open // Scala Media
When there is deflection of Cilia towards the long-side of the Stereocilia, this pulls the hcMET gates ___, allowing ___ K+ to flow in.
open more // more
When there is deflection of Cilia towards the short-side, this relaxes all the Tip Links, allowing the hcMET gates to ___ fully, and it ___ any K+ from flowing in.
close // stops
Ca2+ triggers ___ of neurotransmitters
exocytosis
