Neurophysiology Flashcards
Thickness of the retina
0.2-0.5mm
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Information is transmitted from photoreceptors to bipolar cells to ganglion cells
Lateral flow
Horizontal and amacrine cell integration
feedback
Information from ganglion cells is transmitted back to the photoreceptors via interplexiform cells
Extracellular recording
Studies cells that respond with action potentials (amacrine and ganglion) by inserting an electrode in the retina near the cell without penetrating it
Intracellular recording
Studies cells that respond with graded potentials (photoreceptors, bipolar cells, horizontal cells) by inserting a microelectrode into the cells and recording the change in electrical response
Resting membrane potential of photoreceptors (and why)
-50mV due to potassium diffusing out, sodium diffusing in, and additional sodium channels (CNG channels) for influx at the outer segments
Relative depolarization
Relative excitation, the state of photoreceptors in the dark
G-protein coupled receptors
Membrane proteins characterized by seven transmembrane domains or subunits
Isomerization
The process of absorbing light and undergoing a conformational change from 11-cis to all-trans that triggers phototransduction
Transducin
A g-protein that interacts with photopigments
cGMP purpose
Accumulation at sodium channels in outer segment keeps them partially open
Phosphodiesterase
Released from transducin and cleaves clusters of cGMP ultimately causing hyperpolarization of the cell
On-center bipolar cells
Respond with excitation when light falls on the center and inhibition when light falls on the surround
Glutamates effect on on-center bipolar cells
Inhibitory effect, when light shines, glutamate production decreases and bipolar cell becomes relatively excited
Glutamates effect on off-center bipolar cells
Excitatory
Spatial antagonism
When light exposure elicits opposite responses depending upon whether it falls in the receptive field center or periphery
Invaginating synapse
Formed by on-center bipolar cells with photoreceptors
Conventional flat synapse
Formed by off-center bipolar cells and photoreceptors
Synapse in inner layer of IPL
On-center bipolar cells and ganglion cells
Synapse in outer layer of IPL
Off-center bipolar cells and ganglion cells
Horizontal cells
enhance sharpness of images and contrast under photopic conditions, contributes to spatial summation, and responds with graded potentials
H1 cells
Receive input from M and L cones, with little input from S cones
H2 cells
Receive strong input from S cones, as well as input from M and L cones
What do horizontal cells release
GABA upon excitation by glutamate
GABA effects
Inhibitory to photoreceptors
Excites on center bipolar cells and on center ganglion cells
Midget bipolar cells
receptive field center is a single M or L cone, surrounded by H1 cells
Excellent visual acuity and color vision
Diffuse bipolar cells
Receptive field center is many M and L cones surrounded by H1 cells, making it bad at color vision
S-cone bipolar cells
Synapse only with S cones, in central retina they receive input from a single s cone
Transient response
Shown by many amacrine cells that is a brief increase in activity at stimulus on and offsets
A2 cells
Use glycine, rods
A17 cells
Use GABA, rods
Ganglion cells
Summate electrical activity of the retina
Parvo ganglion cells
Smaller, 75-80% of gc population, one to one connection with midget bipolar cells leading to high spatial resolution and color discrimination
Magno ganglion cells
Larger, 10% of gc population, large receptive fields, receive more from rods
Koniocellular ganglion cells
Small, bistratified, receive from s-cone bipolar cells
Melanopsin ganglion cells
Photosensitive, control pupillary function and circadian rhythm
On center midget bipolar synapse with
On center midget ganglion cell
Off center midget bipolar synapse with
off center midget ganglion cells
On center diffuse bipolar synapse with
on center magno gc
Off center diffuse bipolar synapse with
off center magno gc
s cone bipolar synapse with
koniocellular gc
mGluR6
Receptor found on the ON-center bipolar cell that causes glutamate to have an inhibitory effect
AMPA
Receptor found on OFF-center bipolar cells that causes glutamate to have an excitatory effect
Retino-geniculo-striate pathway
Route from the retina to the dorsal LGN that leads to conscious vision
Spatial summation
As you increase the diameter of the spot of light on the center of an ON cell (Or periphery of an OFF cell), the firing rate will increase until reaching the periphery (or the center)
Which neuron color codes (P or M)?
Parvo
Which neuron has sustained temporal response (P or M)?
Parvo
Which neuron has high temporal sensitivity (P or M)?
Magno
Which neuron has faster transmission speed (P or M)?
Magno
Which neuron shows linearity (P or M)?
Parvo
Which neuron exhibits high spatial sensitivity (P or M)?
Parvo
Which neuron goes to the ventral 2 layers of the LGN (P or M)?
Magno
Which neuron projects to 4 c beta (P or M)?
Parvo