Cell Neuroscience NC Flashcards
Capturing information from the outside world and turning it into neural activity
Transduction
neurons in the eye
Photoreceptors
near point definition
The point at which focusing on a nearing object becomes blurry
neural components of the eye
retina
- fovea
optic disk
optic nerve
optical components of the eye
cornea
aqueous humor
lens
vitreous humor
supporting components of the eye
uveal tract
choroid
pigment
epithslium
ciliary body
iris
sclerawhat provides 80% of the focusing power of the eye and cannot change shape?
the cornea of the eye
what provides 20% of the focusing power of the eye that can change shape?
the lens
is the lens thin or fat, and it it bending light alot or not, when focusing on far objects
less light bending, thin lens
is the lens thin or fat, and it it bending light alot or not, when focusing on near objects
more light bending
fat lens
what effect does light have when it hits photoreceptors
it hyperpolarizes the photoreceptors
What makes the lens fatter when focusing on near objects
the ciliary muscles contract
What happens when eyes change from focusing on a far object to focusing on a near object
the cilary muscles contract to make the lens thickens
accommodation: (definition)
ability to adapt and fix focus on near and far obejctes
why when the ciliary muscles contract does the diameter of the lens get faster? the mechanism
if the circumferonce of the eye decreases, strain on the fibers decrease and the lens rounds up like it naturally wants to do
definition: transformation of light energy into neural activity
phototransduction
doe slight causes the hyperpolarization or depolarization of photoreceptors
hyperpolarization
what does the magnitude of light that hits the eye correspond to
the magnitude of hyperpolarization of the eye
why does the eye hyperpolarize when light hits it? (mechanism)
cGMP is low, and cGMP-gated channels when open keep the flow of Na+ and Ca2+ inwards and potassium out. Potassium is always leaking, so when the cGMP channels are closed and no Ca2+ or Na+ can get in there is a net flux of positive charge out of the cell.
Explain the relative depolarizatio of photoreceptors during darkness
cGMP channels are open allowing Na+ and Ca2+ influx . Even with the leaking K+ this creates a net influx, –> relative depolarization
What are the outer segments of photoreceptors filled with?
disc membrnaes
What are disc membranes covered with
opsin proteins
types of opsins? where are they located?
rhodopsin on rods and cone opsins on cones
What type of opsin proteins have the 3 subtypes of: small, medium, long, OR blue, green and red
cone opsins
explain the activation of rhodopsin on rods
- rhodopsin has a chromophore (trans-retinal) covlently cound to 7th membrane. When the retinal is isomerized the rhodopsin undergoes a conformationsal change that exposes Gt protein binding site
- when Gt bound, the conformational change in rhodopsin triggers a confirmational change in the Gt protein. Which switches the GDP out for GTP on the alpha subunit
- slpha and beta -gamma subunits dissociate and release rhodopsin from the g-proteins
how many transducin (gt proteins) can be activated during the time the rhodopsin is bound to all-trans retinal
can be multiple, more than one
Conformational changes on the G alpha subunit
GDP is switched out for GTP the terminal phosphate on GTP forms hydrgoen bond chains with switch 1 and 2 to prevent interaction with GBY propeller bottom
G-Protein modulation (GEF)
- faciliatats GDP release
- increase activity so there is more G alpha, GTP
what can act as GEF
ligand bound GPCR
G-protein modulation (GDI)
inhibits release of GDP decrease Galpha, GTP activity
G-protein modulation (GAP)
activates intrinsic GTPase activity; decreases Galpha, GTP activity
G-protein modulation (GIP
stops intrinsic GTPase from working; increase activity for more Galpha, GTP
the route of hyperpolarisatino of teh eye
light-activiated opsin (increases) transducin (increases) phosphodiesterase (decreases) cGMP –> close cGMP channels –> hyperpolarisation
what phosphorylates activate Rhodopsin
rhosopsin kinase; on three different sites
what is arrestins function
it binds to phosphorylated rhodopsin causing a conformational change so phosphorylated rhodopsin does cannot activate transducin
what inactivates transducin
RGS9-GB5-R9AP
three ways for light adaptation
- guanylate cyclase
- recoverin
- calmodulin
light adaptation by guanylate cyclase
dark - calcium inhibits guanylate cyclase-activating proteins (GCAPs)
light- induced closing of the cGMP channels decrease calcium (up-regulates GCAPs which in turn up-regulate guanylate cyclase)
what is the fastest most powerful way for light adaptation
guanylate cyclase
light adaptation- recoverin
dark - calcium recoverin inhibits rhodopsin kinase from phosphorylating rhodospsin
light- induced drop in calcium relieves inhibition, low calcium leads to more rapid dhodopsin inactivation, which eventuall leads to more cGMP
light adaptation - calmodulin
dark - calcium binds to cGAMP gated channel and desnsitizes it to cGMP
light- induced dorp in calcium - calmodulin dissociates from the channel making it more sensitive to cGMP (stays open with fewer boun cGMP)
what is responsible for dark adaptation
the replenishing of 11-cis retinal in opsins
explain the replenishment of 11-cis retinal
interphotoreceptor binding protein (IRBP) chaperones retinoids b/w photoreceptors and pigment epithelial cells
photoreceptor disks are continually _____
being replaced - after migrating from soma to end of outer segment
- old ones are removed by pigment epitherlium
have high sensitivity and low intensity vision
rods - night
have low sensitivity and high intensity vision
cones - day
bwetter convergence? rods or cones? what does this do
rods
- better sensitivity
what does teh foveola contain
only cones - no blood vessels to obscure path of light to cones
what cone colour is short
blue
what cone colour is long
red
what cone colour is medium
green
what cones make up the least amount of total percentage of cones
blue/ short
protonopia
type of colour blindess where missing L/red cones
deuteranopia
type of colur blindness hwere missing M/ green cones
what cones are on the what chromosome
M/L red and green - on x chromosome
what is sound
vribrating particles in waves that make teh ear drum vibrate
bones of middle ear and facts
malleas, incus, tapes
smallest bones in body
concentrate vibration increasing pressure 17X
act as levels 13X
middle ear muscles
dampen vibratino of ossicles of body noises
what happens in inner ear
longituinal waves make oval window move in/out, set up transverse waves n basiliar membrane
best frquencies along basiliar membrane
base- high freuencie, narrow sitll
apex: low frequencies; floppy
___ are located on hair cells and deflected by tectorial membrane
stereocilla
what direct growth of stereociulla
kinocillium
how do channels open on stereocilla; what kind of channel
tip links connect hair cells, tensino when pulled to long side which opens channels - hcMET
what happens to stereocilla at low frequencies? high frequncies?
low freuqncies- hyperpolarisationa nd depolarizatin as they wave backa dn forth
hig frequncies- depolarisation adn stay theyre vibrating wuickly - not enough time to go to hyperpolaization
what bathes the scala media
endolymph
what bathes the basal part
peilymph
endolymph is ____rich and _____ poor
K+ rich, Na+ poor
perilymph is ____ rich and ____ poor
Na+ rich and K+ poor
inner hair cell function
carry sound
outer hair cell function
provide amplification
____ causes endolymph lag behind head movement
inertia
inside the semicircular canals the inertia casuing endolymph lag behind head movement causes what to teh cupola and hair cell cilia
causes distortion of floppy cupola and dispalcement of embedded hair cell cilia
whats special about cell bodies located in the dorsal root - the long fibers that transmit info skin to spinal cord?
the action potentials dont need to go through the cell body
what are the long fibers that transmition infor straight from skin to spinal cord called
pseudounipolar fibers
what allows catinos to enter during mechano-transduction
the tretching and deformation of the membrane
mechano sensor cell merkel is ________
shallow
mechano sensor cell is meissner _________
shallow
mechano sensor cell ruffini is ______
deep
mechano sensor cell pacinian is ________
deep
group 1a intrafusal muscle fibers
rapidly adapting and give info about limb movemnt
group 2 intrafusal muscle fibers
sustained response, info about static limb position
Y motor neurosn cause what ___
intrafusal muscles to contract
group______ is located in the golgi tendon organ
group 1b
group 1b sensory affert is woven though _________ and form collagen fibvers that form the tendon
the collagen fibers
_______ fibers conduct touch info not involved with pain
AB pain fibers
what becomes actived to initiate pain signals? when?
nociceptors/ free nerve endings
- after AB fibers are saturated
what channels are activated by capacin? what does this sensation feel like/ mean
TRPV1 channels activated by capacin - spicy food hot
explain the olfactory epithelium
odorants pass over this through air during breathing ect and add to the taste of things
olfiactory cilia studded with ______ has axons that go through _____
odorant receptors whose axons go through cibreifrom platform (porous bone)
what can lead to no sense of smell / ____ and why>
head trauma can sheer odorant receptor axons
no sense of smell = anosmia
how often do olfactor receptor neurson renew? from what?
6-8 weeks, population of neural stem cells
chemicals that provide nutritive, aesthetic, saftey qualities
tastant
how do tastants travel? what do they make contact with ?
travel through saliva and make contact with taste papillase (taste buds lay on top of these)
what are the 5 different tase categories
sour sweet salty bitter umami
taste category: NA+ influc ; voltage gated channels
salty
taste category; H+ influx; voltage gated channels
sour
taste category T1R2 and T1R3 ; 2 g protein with 7 TM receptors that form dimer
sweet
taste category T1R1 and T1R3 with 2 g protein 7 TM each receptors that form dimer
umami
taste category ; TR2 g protein gustducin
bitter
