Lecture 22: vision 1 Flashcards
which love is linked to vision?
occipital
where is the retina located?
back of the eye
is the retina light sensitive?
yes
where to nerve fibres form the retina leave the eye?
love the eye in the optic nerve and synapse in the lateral geniculate nucleus
after leaving the retina where do nerve fibres go?
the visual cortex
what does vision depend on?
light sensitive cells in the retina at the rear of the eye
what focuses light onto the retina?
cornea and lens
what is the fovea?
region where
upper retinal
layers are thinned
whats the order fo the front centre structure of the eye?
cornia
anterior chamber
iris
lens
what is the structure of the retina?
photoreceptors Outer plexiform layer Horizontal cell Bipolar cell Amacrine cell Inner plexiform layer Ganglion cell
how do photoreceptors increase there surface area?
They have an outer segment with stacks of membrane
what do pigment molecules do?
collect light
How many rods and cones do humans have?
120 mil rods
6 mil cones
do nocturnal animals have more or less rods than humans?
more
what do rods do and where are they located?
Rods are more sensitive
to light and occur in the
periphery
what do cones do and where are they located?
Cones respond to different
wavelengths and are found
mainly in the fovea
is the structure of the fovea whats above rods?
cones
what happens to Vertebrate photoreceptors when stimulated ?
they become hyperpolarised
when stimulated, unlike
most receptors that
become depolarised
How many types of rods are there?
1
How many types of cones are there?
3
what colour absorbance is associated with rods?
blue/green
what colour absorbance is associated with cones?
red
green
blue
How many cones can synapse with one bipolar?
one or a few
what do cones have that is small?
small receptive fields for high-acuity colour vision in fovea
How many rods synapse with one bipolar?
several
rods subserve ___ ____ _______
low light vision
what do photoreceptors synapse with?
bipolar cells
what do bipolar produce and what they modulated by?
Bipolars produce graded receptor potentials modulated by horizontal cells
A combination of inputs from photoreceptors and horizontal cells produces what?
two kinds of receptive field in bipolars, on centre and off centre
If spot of light applied to centre of bipolar cells what happens?
on centre cel - excited, large response form ganglion cells
off centre cell - inhibitory, bipolar cell off, ganglion cell inhibited
If a ring of light is applied to bipolar cells what happens?
on centre cell - Bipolar cell inhibited, response from ganglion cell shut down
off centre cell -Bipolar cell excited, ganglion cell responds
what do ganglion cells have and what do they produce?
Ganglion cells also have on-centre and off-centre fields but produce action potentials
where do the axons of ganglion go to?
Their axons go into the optic nerve to the LGN
what do ganglion cell fibres enter?
fibres enter the optic nerve and chiasm
what do fibres from the nasal retina do?
cross over (contralateral)
what happens to fibres from the temporal retina?
remain ipsilateral
