Welcome back.
We're going to continue our consideration of the special senses,
talking about the hearing and vestibular system that are gonna be found in the ear.
We're gonna start off with the auditory system that is gonna detect sounds and
it's going to be detecting sound waves which are gonna be compression and
expansion of air molecules in the forms of waves.
So it's gonna be waves that are expanded air.
And compressed air that are alternating to form waves.
And it's going to be the amplitude of the wave,
the height of the wave that's gonna determine volume of the sound.
And then it's gonna be frequency of the waves that
is going to determine the frequency or the pitch of the sound.
And so that's how we interpret these sound waves into
the noises that we actually hear.
So the auditory system is gonna be able to detect complex sounds
by breaking them into their basic sound frequencies and
then they're obviously gonna be converted into action potentials.
And, volume is going to be relayed by the frequency of action potentials.
So the louder a sound is, the more frequent the action potentials are.
And we'll talk about how pitch, or
the frequency of the sound is gonna be determined, as well.
So now we've got to get involved in the anatomy of the ear,
that's obviously gonna be critically important in to how we hear.
Where the sounds are going to be focused onto the tympanic
membrane, or the ear drum by the auditory canal and
then we're gonna have a set of three bones, the malleus,
incus and stapes that are going to transduce the vibrations
of the tympanic membrane to vibrations in the fluid
of the cochlea which is gonna be in the inner ear.
So here's a zoomed-in portion of the middle ear and
the inner ear, the middle ear being where we have
the three bones that are going to rock next to one another
when the tympanic membrane vibrates from the sounds,
that's gonna cause them, malleus, incus and stapes to rock and
cause the vibrations at the oval window of the cochlea.
So this is zoomed-in picture of the cochlea.
Where we're gonna have two different fluid paths and
we'll see about this in the next figure as well.
But here's the oval window where we have it being vibrated from
the tympanic membrane, transduced by the bones and
then causing the oval window to be vibrated.
And I forgot to mention, but these bones are so
important for amplifying the vibrations.
So that's what their crucial role is.
Because out here in the outer ear we have vibrations
of air, but then we need to cause vibrations in fluid.
Which is gonna be much less efficient and require much more energy to cause the same
amount of vibration of a fluid compared to vibration of the air.
And so, that's the role of these three bones, is to amplify the vibrations from
the air, so that it can cause significant vibrations in the fluid of the cochlea.
So that's what's gonna happen when this oval window is vibrated.
It's gonna be strong enough to transduce the vibrations from the sound
waves in air to vibrations in a fluid.