L4 Visual System Flashcards
Visual system stimuli
food, predator, mate
What defines sensory neuron morphology
its function
Positive feedback in relation to neurons
pre-synaptic neuron activates post-synaptic neuron
What are the types of feedback in the visual system
positive feedforward, negative feedback and negative feedforward
Main retina function
image acquisation
Right hemifield activates
left brain
LGN function
preprocesses visual information
Where does information travel to from the LGN
primary visual cortex
Visual pathways in the cortex
ventral stream and dorsal stream
Ventral stream function
processes object identity
Dorsal stream function
processes object location, speed and direction of movement
Pupil function
regulate amount of light falling on the retina
Lens function
focus image on fovea
Fovea property
part of retina with highest visual acuity
Where are photoreceptors densely packed
Fovea
Rod function
high light sensitivity
Muller cell function
light guides, transmit light to tissue
Retina layers
3 layers of neurons, 2 layers of synapses
Inhibitory retina cells
horizontal and amacrine cells
Synaptic layer OPL
synapses between photoreceptors, bipolar and horizontal
Direct retina pathway
Photoreceptors to bipolar cell to ganglion cell
Synaptic layer IPL
synapses between amacrine, bipolar and ganglion cells
Synaptic layer importance
process of important
Retina synaptic layers
inner and outer plexiform layers
Retina feedforward neurons
photoreceptors, bipolar cells, ganglion cells
Retina feedback neurons
horizontal cells and amacrine cells
Rod activation
dim light
Cone activation
high light
Where does phototransduction occur
outer segment of rod and cones
Photoreceptor response to light
hyperpolarisation
cGMP function in retina
activates channels on photoreceptor membranes
Light on rhodopsin
change in conformation - activates GPCR
cGMP presence in cytoplasm causes
activates channels which open
Phosphodiesterase function
regulates cGMP levels
Channel opening in photoreceptor membrane effect
depolarisation of the membrane
Why do channels on photoreceptor membranes depolarise the membrane
channels are non selective
Light on receptors
less glutamate release
What is the effect of less glutamate release
less activation of bipolar and horizontal cells
Types of bipolar cells
ON and OFF
ON bipolar cells
depolarise when light goes on
OFF bipolar cells
hyperpolarise when light goes on
Photoreceptor neurotransmitter
glutamate
OFF bipolar cell receptor
ionotropic glutamate receptor - excitatory
ON bipolar cell receptor
metabotropic glutamate receptor - inhibitory
Photoreceptors in the dark
continuously depolarised due to inward sodium current
Receptive field
area in the retina which when illuminated activates a visual neuron
Annulus
ring of light with dark centre
Fovea connections
1-1 bipolar cell to photoreceptor
Glutamate on bipolar cell
release hyperpolarises bipolar cell
Stimulated horizontal cell on bipolar cell
bipolar cell is less inhibited
Bipolar cell termination
inner flexiform layer
Asymmetric ganglion cell dendritic tree function
detect motion in specific plane of direction
Ganglion cell function
high sensitivity vision
Ganglion cell firing
action potentials
Graded potentials in the retina
Bipolar cells and photoreceptors
