Special Senses Flashcards
What is sound?
-audible variations in air pressure.
Air is compressed (made more dense) when
when obj is moving toward a point in space
Air is rarefied (made less dense) when
an obj is moving away from a point in space.
intensity
- loudness
- measured in pascals
- human range is from less than a billionth atm pressure (0 decibels) to 10^13 atm pressure (130 decibels)
(T/F) Sound waves also have intensity measures as pressure of the wave (Pascals)
T
Pitch
-frequency
-measured in Hz/kHz
-pitch is equal to the number of crests that pass a point in a second (aka cycles per second or Hz)
100 cps = 1 kHz
-incr vibrations, incr pitch
auricle
- part of outer ear
- cartilage covered by skin
- impt in locating sounds in space
auditory canal
- aka ear canal
- part of outer ear
tympanic membrane
- part of outer eat
- outer layer of ear drum
ear drum located in
middle ear
cavity (tympanic cavity)
-in middle ear
houses the ossicles: malleus (attached to ear drum), incus, stapes (smallest bone in the body)
oval window
- part of the middle ear
- connect middle ear to the inner ear
semicircular canals
- part of inner ear
- filled with fluid attach to cochlea
- sends info about balance and head position
cochlea
- part of inner ear
- spiral shaped organ where sound transduction takes place
eustachian tube
part of inner ear
-drains fluid from the inner ear into the throat behind the nose
scala media
middle chamber of cochlea
-houses the organ of corti that sits on the basilar membrane
scale vestibuli
- top chamber of the cochlea
- separate by scala media by reissners membrane
reissners membrane
separates scala media from scala vestibuli
scale tympani
- bottom chamber of cochlea
- separated by scala media by basilar membrane
organ of corti
- complex arrangement of cells and accessory xtures that is supported by the basilar membrane
- compromises the sensory cells of the ear
- when basilar membrane vibrates in response to sound, the entire organ or corti moves up and down
basilar membrane
- separates scale media from scala tymapni
- supports organ of corti
- vibrates in response to sound
- flexible and has unique characteristics that help its ability to respond to sound
tectorial membrane
-overhanging xture and sits immediately above the organ of corti
how does the ear communicate sound
basicar membrane vibrates in response to sound. forces organ of corti upward against tectorial membrane. tectorial membrane exerts a sheering force on apical membrane of sensory cells in organ of corti —this communicates sound
basicar membrane is wider and more flexible at its
apex
basilar membrane is narrower and stiffer at its
base
(T/F) when sound is transfered to the basilar membrane, the distance it transduced along the length of the membrane does not depend on frequency.
F- it does depend on freq
basilar membrane with incr freq
base vibrates a lot and dissipates the energy of the soundwave
basilar membrane with decr freq
sound travels to apex
(T/F) the tectorial membrane has a tonotopic map
F- the basilar membrane
outer hair cells
- 3 of them
- do not contribute to sensory transduction in ear but are important for adjusting the stiffness (tunning) of the basilar membrane
inner hair cell
- 1 of them
- completely carries out auditory transduction.
- depolarized cell with a hair bundle
Can hair cells fire APs?
cannot fire AP but it’s membrane pot fluctuates in response to sound and release NTs onto post syn nerve ending that synapses onto its base
Steps in auditory conduction
1-bundel deflection 2- transduction current 3-Receptor pot 4-Ca2+ current 5-glutamate release 6-EPSP 7-APs
tip link
a fine process connect each stereocilia in the hair bundle to the next tallest one
-attached to mechanically gated ion channel
How does bundle deflection open gate
when hair bundle is deflected bc of vibration of basilar membrane, the tip-link pulls on a mechanically gates ion channel present on stereocilia, causing it to open.
- cations flow down electrochem gradien
- this cation flow = transduction current
transduction current
- when cations flow down electrochem gradient from channels on stereocilia
- transduction current causes receptor potential
receptor potential
-caused by transduction current
activates voltage gated ion channels on basolateral surface of hair cell.
why is Ca2+ current impt?
bc this is what supports glutamate NT release from pre syn terminals
wavelength is responsible for
perception of color
amplitude is responsible for
-intensity– perception of brightness
visible light spectrum
violet-blue-green-yellow-orange-red
400 nm –>700 nm
this is at 10^-6 meters of electromag spectrum
electromag spectrum
gamma-xrays-uv-visible light-IR-radar-radiowaves-AC circuits
ciliary body and lens
divide the eye into posterior (vitreous) cavity and anterior cavity (which has anterior and posterior chambers)
aq humor
- circulates within the eye
- diffuses through walls of anterior chamber
- re enters circulation
vitreous humor
- fills posterior cavity
- not recycled, permanent fluid
the lens and how it helps us focus
- light is refracted as it passes through the lens
- closer the light source, the longer the focal distance, flatter the lens
- further the light source, the rounder the lens, the shorter the focal distance
retina made up of
rods, cones, pigmented epithelium, bipolar & ganglion cells and horizontal and amocrine cells.
pigmented epithelium
- epithelial cells that contain melanin
- appears dark in histo prep
- helps prevent light from reflecting back through the retina–> which would lead to image distortion and poor visual acuity
- also a storage for vit A (precursor to the photopigments)
bipolar cells & ganglion cells
converge and integrate APs
bipolar cells- transmit their info to the ganglion cells
ganglion cells- extend their axons across the surface of the retina and these fibers make up the optic nerve. these are the output of the retina
optic disk
- central pale portion of the retina where the central retinal artery and vein merge
- blind spot– has no photoreceptors
fovea
dense area of retina
-region of highest acuity
which photoreceptors carry out phototransduction?
rods and cones
levels cones present
- mostly present in fovea
- low levels everywhere else (except blind spot_
levels rods present
- none in fovea
- increase as we move away from fovea to more periphery of retina and then it falls slowly but still maintained at relatively high levels
why are there more stars off center?
focus with rods instead of cones bc better night vision and rods are located on more periphery of retina
(T/F) Light only needs to pass through some layers of the retina before it can reach the photo Rs
F- light must pass through all layers of the retina
organization of retina from front of the eye back
ganglion cells
- bipolar cells
- rods and cones
- pigmented epithelium
- choriod
optic nerve
- perforates the optic disk
- made up of ganglion cell fibers
- transmits the info that was originally transduced by the photoRs to the primary sensory areas of the brain
rods
very low spatial acuity
- extremely sensitive to light
- monochromatic night vision
cones
- high spatial resolution
- insensitive to light –> specialized for acuity
- color, R,G,B
at the lowest level of light what happens
- only rods acivated
- scotopic vision
- sock matching problem
- poor resolution
- no perception of color bc cones not involved
scotopic vision
rod mediated vision at lowest level of light, no cones
as illumation increases what happens
-cones become more and more dominant
rods decrease = photopic vision
the membrane pot of indiv rods can not longer function bc cell membrane channels are closed
photopic vision
when rods decrease because their response to light is saturated with increasing levels of illumination
so no rods, only cones
mesopic vision
levels of light which both rods and cones contribute
ex-twilight
macular degeneration
loss of cone function in elderly
-they are legally blind even though they may have cone
(T/F) rods converge on bipolar cells
T
Rods or cones exhibit less convergence
cones
convergence makes rods better at what? and why
detecting light because small signals from many rods are added together to generate a large response
convergence in rods makes them worse at what? and why
spatial resolution and acuity bc the stim the source of a single rod bipolar cell or retinal ganglion cell could come from anywhere within a relatively large area of the retinal surface
what are photopigments and which pigments do they contain?
-the outer segments of each photoreceptor is packed with membranous disks that contain the light sensitive pigments which is opsin & retinol (11-cisretinol)
rhodopsin
photopigment in rods
scotopsin + 11-cis retinol
retinol
- identical in every photo R but the protein portion of the molecules varies slightly (vary in AA req) and this alters the properties of each photopigment
- comes specialized for B, G or R wavelengths
describe the diff in AA between blue and rhodopsin
large difference
describe the diff in AA bw G and B
many differences byt not as many as rhodopsin and B
describe the diff in AA bw R and G
very similar
why do no black bands appear in the rainbow?
because all wavelengths (rods, R, G and B) overlap in the full visible spectrum
rod adaptation to light (slow/fast)?
slow
cone adaptation to light (slow/fast)?
fast
what form of rhodopsin is the only form that fits comfortably in opsin?
11-cis- retinol
what happens when a photon is absorbed by retinol?
-changes conf from 11 cis retinal to all trans retinol
what does all trans retinal cause?
-bleeching = causes retinol and opsin to dissoc bc all trans can’t fit comfortably in opsin molecule
the restoration of all trans retinal back to 11 cis retinal is a passive process. (T/F)
F- it is ATP dependent
it is also enzyme driven
what needs to happen in order for us to generate new rhodopsin?
11 cis retinal needs to be restored
what is present in outer segment of a rod?
membranous disks and cGMP gated Na+ channels
what is present in the inner segment of a rod?
- Na/K ATPase
- K channels
when does a rod experience dark current
when no light present
dark current
when Na channels open, Na enters outer segment and K leaves in inner segment.
-this cycle of pos charges entering and leaving creates a flux called dark current.
what does incr cGMP do?
keep cGMP gated Na channels open
when is the cell depolarized? (dark or light)
in the dark becasue that’s when pos charges enter
phototransduction in light process
1- light strikes rhodopsin and activates G protein (transducin) and binds GTP
2- alpha subunit activated cGMP PDE
3- PDE breaks down cGMP to 5’ cGMP which reduces the conc
4-decr cGMP causes Na channels to close in plasma membrane of outer segment. Inner segment K continues to be pumped out of rod which hyperpolarizes the cell
what happens in light basically
-decr conc cGMP in outer segment, closure of cGMP gated Na channels and hyperpolarization of photoR (disrupts dark current)
what happens to hyperpolarization as we incr intensity of light?
incr intensity of hyperpolarization
(T/F) The depolarization in the dark leads to constitutive release of NT
T
when is the release of NT inhibited?
in the light
(T/F) the amount of energy a given sensory R responds to in normal function is known as an “adequate stim”
T
(T/F) R pots are all in one phenomena
F
(T/F) When freq of APs along sensory neurons is const as long as a stim continues, it is called adaptation.
F
(T/F) Modality refers to the intensity of a given stim
F
