Test 2 Review Powerpoint Flashcards
Reflection
important because most of what we see is light that has been reflected off objects in the environment
Absorption
this is the mechanism by which photoreceptors obtain energy from light to change membrane potential
Refraction
*****light is bent as it passes through different media other than air. E.g., water or glasses
which colors visible light have which freq
cooler colors=high freq
warmer colors=low freq
pupil
opening where light enters eye
sclera
white of eye
iris
smooth muscle; gives color to eye
optic nerve
bundle of axons from the retina; turns into optic tract after chiasm
cataracts
clouding of the lens
fixing myopia
short sighted: concave lens
fixing hyperopia
far sighted: convex lens
ciliary muscle
when contracted, strains eyes, lens becomes rounder and thicker to see things up close, zonule fibers loosen
accommodation: refractive power bringing rays into focus on retina by changing shape of lens
conjunctiva
membrane that folds back from inside of eyelids and attaches to sclera
macula
central vision, part of the retina, high quality of central vision because there are no blood vessels
fovea
- decrease in number of rods, increase in number of cones
- decrease in convergence of photoreceptors to ganglion (one to one ratio around) so increased acuity
- displacement of cells above photoreceptors (pit in retina)
aqueous humor
watery fluid that nourishes cornea; between cornea and lens
vitreous humor
more viscous jelly-like fluid, in between lens and retina, keeps eyeball spherical
visual acuity
the ability of the eye to distinguish between two points near each other
scotopic conditions
nighttime lighting
rods
photopic conditions
daytime lighting
cones
therefore much greater spacial sensitivity on central retina
mesopic conditions
intermediate light levels (indoor lighting, outdoor traffic lighting at night)
both rods and cones
rods or cones in the fovea?
most cones in fovea; no rods in fovea
fat vs round lens
fat lens lets you see things up close
pathway to retina
ganglion cells (outermost in eye), bipolar cells, photoreceptors
amacrine cells
modify relationship between ganglion and bipolar
horizontal cell
mediate relationship between bipolar and photoreceptors
rods
highest concentration: periphery
function at what level of light?: low
number of photopigments? 1
more sensitive to light
cones
highest concentration: fovea
function at what level of light?: high
number of photopigments?: 3
more sensitive to almost anything besides light: color perception, etc
in the dark, photoreceptors are…
depolarized due to a steady influx of Na+, which causes glutamate release
cGMP (cyclic guanosine monophosphate)
cGMP is second messenger that keeps NA+ channels open
When struck by light, rhodopsin has second messenger cascade that inactivates cGMP, so Na+ channels close, neuron hyperpolarizes, glutamate release stops
phototransduction
light activates retina, opsin changes shape, second messenger deactivates cGMP, Na+ channels close, neuron hyperpolarizes, glutamate release ceases
Receptive fields
The area of the retina that, when stimulated with light, changes the cell’s membrane potential (bipolar, ganglion cells)
The area of the visual field that modulates a neuron’s activity when it contains the appropriate stimulus (striate cortex)
on/off cells
the stimulus that will maximally activate center
on=light
off=dark
types of ganglion cells
m type, p-type, non m non p
m type ganglion cell
around 5% of ganglion cells larger receptor field transient response more sensitive to low contrast stimuli specialized for movement
p type
around 90% of ganglion cells
smaller receptive field
sensitive to diff in wavelength (color)
specialized for edge detection
LGN
in thalamus
layers of each eye (1-6)
segregated info into cortex
not binocular
v1
except for layer 4, binocular neurons
perpendicular orientation=orientation
different orientation=go tangentially (aka going across like vertical stripes, parallel) in a cortical module
layer iv
input from lgn
occular dominance columns
superficial layers (II-III)
cytochrome oxidase blobs (object color) (used to label spots on brain) cortical outputs (V2, MT)
Deep layers (V and VI)
Subcortical outputs (LGN, Superior Colliculus)
orientation selectivity
respond maximally to a particular orientation
center surround (simple cells)
no center surround (complex)
object shape
direction selectivity
respond maximally to a stimulus moving in a particular direction
object motion
blob receptive fields
respond maximally to particular wavelengths but not orientation or direction
object color
path to striate cortex (v1): magnocellular pathway (motion)
retina: m type ganglion cells
lgn: magnocellular
v1: layer IVC & layer IVB or Blob
cortex
path to striate cortex (v1): blob pathway (color)
retina: nonM-non- ganglion cells
LGB: koniocellular
v1:Blob
cortex
parvo-interblob pathway (shape)
retina: p type ganglion cells
LGN: parvocellular
V1: Layer IVC & interblob or blob
cortex
parallel processing in v1
magnocellular pathway (motion) blob pathway (color) parvo-interblob pathway (shape)
ventral stream
object and visual identification/recognition
dorsal stream
object’s spacial location relative to viewer
Visual shape, color areas
V1, V2, V3
Visual perception, memory
V4, IT
Visual motion
MT, MST
pinna
part of ear used for sound localization in vertical plane using interaural differences
collects sound waves into ear canal in vertical plane
tympanic membrane separates outer ear from inner ear
ossicles
middle ear
bones to amplify force on oval window (sound force amplification)
pathway audition
sound waves move tympanic membrane»_space;
tympanic membrane moves ossicles>
ossicles move membrane at oval window»
motion at oval window moves fluid in cochlea»
movement of fluid in cochlea causes response in sensory neurons
oval window
hole in bone of skull which takes input from tympanic membrane and sends to cochlea
cochlea
transforms physical motion of oval window vibrating into neural response
basilar membrane
stiff by base, flatter and floppier out (flipper)
base=high req
apex=low frequency
establishes place code (where on membrane establishes a location)
hair cells
form synapse on spiral ganglion cells
inner and outer ear
inner hair cells
more highly innervated
majority info leaving cochlea
outer hair cells
amplify movement of basilar membrane
cochlear amplifier
can shorten/lengthen hair cells with motor proteins
antibiotics like kanamycin can damage
sound transduction how
movement of basilar membrane and tectorial causes stereocilia hairs to bend
bending one direction=depolarization, bending in other direction=hyperpolarization
bending causes K+ channels open, k+ influx»_space; Ca++, release NT, depolarizes
other direction no NT, hyperpolarizes
auditory pathway
inner hair cells spiral ganglion neurons cochlear nucleus superior olive inferior colliculus MGN (thalamus) A1 cortex after superior olive=bilateral input
high intensity sounds
louder
produce a greater firing rate because more auditory
more auditory neurons are activated because the basilar membrane will move more in response to louder sounds
neurons are activated
place code
high frequencies
tonotopic organization helps use location to figure out frequency
high freq doesnt travel as far on basilar membrane so this is easier
phase locking
low frequencies
consistent firing of neuron in same place
phase locked in every cycle, or every other, or other thrid etc
horizontal localization
interaural time diff
interaural intensity diff
uses info from both ears
thus superior olive and up
vertical localization
curves of pinna
info from one ear
bumps and ridges in ear produce reflections of entering sound, causing delays as sound moves away vertically
interaural time diff
sound from right side will arrive at left ear and detection of delay helps us locate sound
interaural intensity diff
intensity greater on the side sound comes from
sensory receptors
mechanoreceptors, thermoreceptors, nocireceptors (pain), proprioceptors
Meissner’s corpuscle
rapidly adapting, small receptive field
pacinian corpuscle
rapidly adapting, large receptive field
2 pt discrimination depends on
receptor density (denser=better) cortical representation (more=better) number of receptive types size of receptive fields (smaller=better)
sensory information
dorsal root,
dorsal root ganglion
motor info
ventral root
herpes zoster virus
shingles
affects dermatome on one side of body
left dermatome
spinal cord (segmented) cervical, thoracic, lumbar, sacral
right dermatome
skin, one to one correspondance between dermatomes and spinal segments
