Ch 6 &7 Flashcards
photoreceptor
biological sensors of light including rod & cone photoreceptors
sensory transduction
process by which an external stimulus is converted into a change in electrical activity of sensory neurons or other sensory cells
rod photoreceptors
unusual neurons that fire no APs, w unusually short axon & possess, instead of dendrites, rod shaped outer segment, located in periphery of retina, sensitive to dim light
cone photoreceptors
2nd type of photoreceptor w cone shaped outer segment, mainly in fovea (center of retina), less sensitive to light
blind spot
location of visual field where you can’t detect visual stimuli (while looking through one eye) bc corresponding location on retina (optic nerve head) lacks photoreceptors
macula
lateral to the blindspot, a roughly circular, more darkly pigmented region of retina devoid of underlying blood vessels, contains fovea
fovea
small region of retina that (in humans) contains very high density of cones & very few rods
rhodopsin
photosensitive pigment in rods
optic nerve head
location where axons of retinal ganglion cells cross thru retina to exit eye & enter optic nerve, creates blind spot
retina
multilayered neural structure at back of eye contains photoreceptors, retinal interneurons, & neurons that project thru optic nerve to brain
olfactory bulb
most rostral part of telencephalon in most vertebrates, located on inferior surface of frontal lobe in humans; receives inputs from olfactory epithelium & projects olfactory cortex
olfactory epithelium
layer of cells in roof of nasal cavity that houses olfactory sensory neurons
olfactory sensory neuron
neurons in olfactory epithelium that express olfactory receptor molecules & project olfactory bulb
tympanic membrane
thin membrane separating ear canal from middle ear, known as eardrum, vibrates in response to airborne sounds
malleus
one of middle ear bones attached to tympanic membrane
incus
one of middle ear bones; connects malleus to stapes
stapes
one of middle ear bones; attaches to oval window
oval window
thin membrane covering entrance of cochlea
round window
thin membrane covering basal end of scala tympana; always vibrates together with oval window but in opposite direction
cochlea
spiraling, tubular part of inner ear responsible for sensing sounds
scala vestibuli
half of cochlear tube that extends from oval window to top (apex) of cochlea
scala media
fluid filled compartment in cochlea , between scala vestibuli & scala tympani
scala tympani
half of cochlear tube that extends from top (apex) of cochlea to round window
tectorial membrane
relatively thick membrane that lies on top of hair cells of basilar membrane
stereocilia
“hairs” of hair cells, actually microvilli, rather than cilia
hair cell
sensory cells that sit on top of the basilar membrane of the cochlea & extend stereocilia into the scala media or, in the case of the outer hair cells, the tectorial membrane; thy are also found in the vestibule and semicircular canals
inner hair cell
the hair cells closest to the center of the spiraling cochlea; they sense vibrations of the basilar membrane
outer hair cell
three rows of hair cells furthest away from the center of the spiraling cochlea; main function is to amplify vibrations of basilar membrane & thus increase acoustic sensitivity
basilar membrane
a thin membrane inside the cochlea on top of which inner & outer hair cells sit
tip link
thin filament that connects tip of one stereocilium to the adjacent, taller stereocilium; it is linked to an ion channel that opens when stereocilia are bent toward the tallest stereocilium
the blind spot
region of the retina where axons leave the retina & enter the optic nerve
Photoreceptors respond differently to a stimulation than typical neurons. which of the following is the difference
in response to a stimulus, photoreceptors hyperpolarize
hair cell depolarization in inner ear is normally the result of
deflection by fluid movement in the cochlea
olfaction, sense of smell, used by an organism for which of the following purposes
a) detection of predators
b) identification of food sources
c) mate identification
answer: all of the above
what is the primary function of the round window of the cochlea
to allow for displacement of oval window by relieving pressure in the cochlea
consider the auditory system. place following structures in order based on sequence that they are involved in auditory transduction
1 pinna
2 tympanic membrane
3 malleus
4 stapes
5 oval window
6 cochlea
process of converting external signal to neural signal is called _________.
transduction
the loss of part or all of your sense of smell is known as _________.
anosmia
what is absorption of light
transfer of light energy to a particle or surface
which cells in retina have axons that leave retina
ganglion cells
most of eyes refractive power is accomplished by _______.
cornea
what is the difference between on-center ganglion cells & off-center ganglion cells?
on receive input from on bipolar cells while off receive input from off bipolar cells
Most of eyes refractive power accomplished by what structure?
Cornea
How do we see color?
color of light determined by wavelength (red- longer wavelength, blue- shorter wavelength); white when all wavelengths reflected, black when all wavelengths absorbed.
how many rods vs cones in humans?
about 120 million rods vs. 6 million cones
Types of Cones
1) S-cones
2) M-cones
3) L-cones
S-cones respond
maximally to 425 nm light (dark blue); most sensitive to short wavelengths.
M-cones respond
maximalllyto green light (about 530 nm); respond best to medium wavelengths.
L-cones respond
best to yellow light (about 560 nm wavelength); respond best to longest wavelengths in visible spectrum.
Rods are
maximally sensitive to blue & green wavelengths but are NOT used in color vision
Which cells in eye are synaptically connected to photoreceptors?
bipolar cells (cones & rods decrease rate of glutamate release on exposure of light & synapse on bipolar cells with metabotropic glutamate receptors that elicit hyperpolarization.
Off-bipolar cell
cones make additional synapses to inotropic bipolar cell (OFF-bipolar) bc releases glutamate when exposed to light & more when light turns off
ON-bipolar cells
both rods & cones synapse to these cells (rods exclusively synapse to this type of cell ONLY); have metabotropic glutamate receptors
cone bipolar cells release glutamate directly to
retinal ganglion cells that have long axons that project thru optic nerve to multiple targets in brain, including superior colliculi (optic tectum) & Lateral geniculate nucleus
amacrine cell
rod bipolar cells synapse onto amacrine cells that synapse onto cone bipolar cells
information from rod bipolar cells must pass thru
amacrine & cone bipolar cells to get out of retina
glomeruli
one of many spherical structures in olfactory bulb where axons of olfactory sensory neurons synapse onto the dendrites of mitral cells
odorant receptors
olfactory receptor molecules (G protein-coupled receptors resembling opsin) in cilia which odorants bind to, which then trigger changes in membrane potential of olfactory receptor neurons
odorant binding proteins
transport odorants through mucus to olfactory cilia (other odorants dissolve in mucus & reach cilia by diffusion)
In what sense might it be better to think of photoreceptors as darkness sensors rather than light sensors?
one can say vertebrate photoreceptors sense darkness bc they are depolarized in the dark (“dark current”) & become less depolarized when stimulated by photons
What is “color blindness”, how is it corrected?
a deficiency in way you see color, you have difficulty distinguishing certain colors (blue, yellow, red, & green (r & g most common type followed by b & y); there is no treatment; most common type is inherited (defects in genes containing instructions for making photopigments in cones.
more light means more neurotransmitters released in
rod bipolar cells
most colorblind individuals have effective or missing
L & M cones
spatial receptive field
region of space where visual stimuli must be presented if they are to modify neuron’s activity
rod system vs. cone system
you can think of the
rod system as being specialized for vision in low light, sacrificing spatial detail and
color; whereas the cone system is specialized for high-resolution color vision but goes
offline when it gets dark.
light-sensitive retinal ganglion cells express melanopsin a
photosensitive pigment that is related to the opsins expressed in rods and
cones but responds to light much more slowly
each
olfactory receptor type binds to a specific molecular feature or
epitope
