the eye Flashcards
how should you write the figure for BMI
to 1 dp unless whole number answer
what happens when glutamate is released between the rod and bipolar cell
if glutamate is released between bipolar and rod cell the bipolar cell doesnt send a message- cant detect visual stimulus. glutamate is an inhibitory neurotransmitter- action potential not reached in bipolar cell
whats an exitatory neurotransmitter
stimulates the postsynaptic neurone to produce an action potential
whats an inhibatory neurotransmitter
prevents postsynaptic neurone producing an action potential- found in rod cells
how does the lens focus the image better on the retina?
cillary muscles change its thickness
why do rod cells generate images in black and white?
they cant distinguish between wavelengths on detect absence or presence of light, but can also detect brightness of light
role of rhodopsin in retinas
pigment that detects light
when it detects light it bleaches-breaks down to form retinal and opsin
whether or not rhodopsin bleaches determines whether or not sodium ions open or close
how does bleaching of rhodopsin mean an action potential is generated?
if its bleached sodium channels close
sodium ions wont diffuse back into rod cell
so the membrane is hyperpolarised
so no inhibitory neurotransmitter released
so action potential is generated in bipolar cell
why isnt an action potential generated when rhodopsin isnt bleached
sodium ion channels are open
so sodium ions diffuse back into rod cell, depolarising membrane
inhibitory neurotransmitter released, inhibiting action potential in bipolar cell
what does release of glutamate do to bipolar cell?
prevents bipolar neurone from being depolarised so no impulse travels to the brain
State the order of neurons involved in responding to light and communicating to the brain, starting with the rod cells
rod cell, bipolar cell, optic nerve
Describe the response of rod cells to darkness
if light isnt detected the pigment rhodopsin wont become bleached
sodium channels in rod cell will be open
sodium ions will flow back into rod cell, depolarising rod cell membrane
glutamate will be released, inhibitory neurotransmitter meaning bipolar cell wont become depolarised and action potential wont be generated
Describe the response of rod cells to light
when lights detected by rhodopsin they become bleached
sodium channels will be closed so wont flow back into rod cell
inhibitory neurotransmitter wont be released
action potential in bipolar cell will be generated
Explain why visual acuity (how sharp the image is) is better with our colour vision i.e. cones than with our grayscale vision i.e. our rods
rod cells cant distinguish between wavelengths only detect presence or absence of light
multiple rod cells connected to same bipolar cell wheras only one cone cell connected to one bipolar cell
where are rod cells usually found
outer retina
how can cone cells detect colour
theyre sensitive to dif wavelengths of visible light
what’re receptors?
specialised cells that generate a nerve impulse in a sensory neurone when exposed to particular stimulus
what happens when radial muscles contract & in response to what?
pupils dialate in response to dim light
what happens when circular muscles contract and in response to what?
pupils constrict in response to bright light
whatre rod and cone cells
photoreceptors/light receptors
which region of the retina is light focused on after it enters the pupil and what does this region contain
fovea
contains many photoreceptors
(photoreceptors also found elsewhere in eye)
how is the shape of the lens controlled & why does the lens shape change
cillary muscles (attached to suspensory ligaments)
changes to allow lens to focus light reflected from objects thatre diff distances from the eye
how do action potentials in photoreceptors reach the brain?
via the optic nerve
what is the blind spot?
region where optic nerve leaves the eye, no photoreceptors here
