Sensory Physiology 2 Flashcards
Sound waves can be seen as vibrations of a
tuning fork.
The larger the amplitude of the oscillations, the
louder the sound
how is sound measured?
measured in Decibels (dB).
The more frequent the oscillations (frequency) the
higher pitched the sound. This is measured in Hertz (Hz).
how many hz is the human range?
on average 20 to 20,000 Hz, although there is natural variation especially at higher frequencies.
a gradual loss of sensitivity to higher frequencies with age is ….
… normal
The dynamic range is
0 dB to 120-130 dB for middle frequencies between 1,000 – 2,000 Hz
For lower and higher frequencies, the dynamic is
narrowed.
All sound above …
90 dB are damaging to the inner ear with irreversible damage above 120 dB.
Normal conversation/speech is around
60 dB.
The size of vocal chords affects …
… the pitfch of voice
Vocal folds are controlled via
recurrent laryngeal branch of the vagus nerve.
what are the vocal folds composed of?
They are composed of twin infoldings of mucous membrane stretched horizontally, from back to front, across the larynx.
how do the vocal folds vibrate?
They vibrate, modulating the flow of air being expelled from the lungs during phonation.
The throat, nose/mouth cavities act as
resonating chambers.
Most arthropods use antennae to
detect sounds.
Nearby sound drives
fast-moving air molecules into the hairs on the mosquito’s antenna, causing the antennal shaft to vibrate (similar to a tuning fork).
The outer and middle parts of the ear are both
air filled
The outer and middle parts of the ear are both air filled, whilst the inner ear is
fluid filled.
The fluid has much greater …
inertia than the air.
How much sound do you hear when underwater?
If sound waves hit the surface of the fluid directly. Almost all the energy of the wave would be reflected back from the surface of the fluid and very little would be transmitted into the inner ear itself.
Sound waves are detected by …
… the ear
The pinna acts to …
direct the sound wave towards the auditory canal where it strikes the tympanim (ear drum), which forms the boundary between the outer and the middle ear.
what is the tympanum ?
The tympanum is a tightly stretched membrane.
when the sound wave hits the tympanum it is made to…
… vibrate at the same frequency as the oscillations of the sound wave.
when the sound wave hits the tympanum it is made to vibrate at the same frequency as the oscillations of the sound wave.
These movement cause …
… the three ossicles (‘little bones’, the malleus, incus, and stapes (hammer, anvil, and stirrup)) of the middle ear to move, again at the same frequency, and to transmit the mechanical stimulus to the inner ear.
The middle ear ensures
sound can overcome the greater inertia presented by the fluid filled inner ear.
The middle ear does this through …
area ratio and level action.
whagts the oval widiow?
membrane covering the inner ear
The oval window (membrane covering the inner ear) has an area
17 times smaller than that of the tympanum.
The oval window (membrane covering the inner ear) has an area 17 times smaller than that of the tympanum. So, the force exerted on the tympanum is
increased 17-fold when transmitted to the oval window.
The 3 ossicles act as …
a level system to magnify the force of transmission by about 1.2-fold.
The oval window or fenestra vestibuli is
a connective tissue membrane-covered opening from the middle ear to the cochlea of the inner ear.
A travelling wave, as its name suggests, is
one that moves along, a good example being the wave on the seashore (as opposed to a stationary wave, which does not move, an example being the wave seen on a violin string).
Inside, the cochlea is divided into
three fluid-filled chambers called scalae (‘scala’ means staircase in Italian): the scala vestibuli and scala tympani,
Inside, the cochlea is divided into three fluid-filled chambers called scalae (‘scala’ means staircase in Italian): the scala vestibuli and scala tympani, both of which are filled with
perilymph that is rich in Na+ and low in K+, and the scala media, which is filled with endolymph that is rich in K+ and low in Na+.
The cochlea is rather like the spiral of
a snail shell with about 2.5 turns and about the size of a large pea.
Unravelled, the whole structure of the cochlea is approximately
32 mm in length.
High frequency waves (high pitch) do not
travel far into the cochlea. Low frequency waves (low pitch) travel the furthest.
The sense organ itself is
the organ of Corti, which sits in the basilar membrane, thus dividing the scala media from the scala tympani.
Oscillations of the oval window set up a
travelling wave within the fluid of the scala vestibuli that causes the basilar membrane to oscillate up and down.
The basilar membrane changes along
its length such that it is narrow and stiff at the base, adjacent to the oval window, and wide and floppy at the apex.
The organ of Corti comprises two groups of hair cells
a single row of inner hair cells and three rows of outer hair cells.
The stereocilia (‘hairs’) of the hair cells contact
the membrane above them (tectorial membrane).
As the basilar membrane rises, …
the tectorial membrane moves outwards and the stereocilia are bent. As the basilar membrane descends, the stereocilia straighten up. Therefore, the hair cells will be bending in synchrony with the frequency of the sound waves.
As the stereocilia are bent in one direction, the hair cells
depolarize
As the stereocilia are bent in one direction, the hair cells depolarize
as they return in the reverse direction….
the channels close again and the flow of K+ is halted
As the stereocilia are bent in one direction, the hair cells depolarize; as they return in the reverse direction the channels close again and the flow of K+ is halted.
This means that the receptor potential in th e hair cells
depolarizes and repolarizes at the same frequency as the incoming sound
The mechanoelectrical transduction channel is …
… nonselective for cations with ion fluxes in hair cells composed predominantly of Ca2+ and K+.
Upon normal stimulation,
ions flow from the extracellular space containing endolymph into the hair cell.
Note the stretching of the activation gate: drives
K+ in
Age-related hearing decline.
Note the loss of:
- hearing threshold and
- frequency detection
The semicircular canals (left, in a) are arranged so
that they can detect:
movements of the heads in
the LM axis.
the AP axis.
the SI axis.
rotational movements
The utricle and saccule (right, in b) are arranged so
that they can detect:
linear accelerations in
the horizontal axis.
the vertical axis.
and thus gravity
When motion/movement/rotation occurs:
inertia moves the cupula in opposite direction
When motion/movement/rotation occurs:
inertia moves the cupula in opposite direction, this creates
a sudden flow of endolymph,
the sudden flow of endolymph is involved in
endolymph is K+-rich,
opening of transduction channels,
depolarisation of the hairs,
excitation of the afferent fibers (CN VIII).
endolymph is rich in…
K+
The cupula is a
gelatinous mass. It has inertia
The crista ampullaris is a
a ridge of tissue, to which hair cells are anchored to
Axons convey action potentials from…
the hair cells to the vestibular nerve.
what is the auditory vestibular nerve used for?
For both sound and balance.
When the head is rotating or moving, whayt contriols eye movements?
CN VIII
When the head is rotating or moving, CN VIII controls eye movements:
what are these?
- slow (pursuit),
- rapid (saccade).
This induces a nystagmus.
What is a cochlear implant?
a surgically implanted neuroprosthesis that provides a person who has moderate-to-profound sensorineural hearing loss with sound perception.
