Vision 1 Practice Questions
Which second messenger is vital to human vision?
cGMP
Part of the CNS that processes visual info
What is the retina?
Use NIR to restore/supplement visual function in patients with retinal degeneration
You shine a light just on the center cone (dark annulus), what will be effect on the center cone? The surrounding cones? The net effect on the center?
Center: large hyperpolarization
Surrounding: large depolarization
Net: very little glutamate release
Mostly responsible for color vision
What are cones?
Name and define an example of an encoding strategy
1. range fractionation - multiple receptors that respond over different amplitude levels
2. logarithmic encoding - as stimulus intensity increases, spike frequency increases, but only get a small change in firing rate
3. adaptation - changes in range in which cell responds to
All features that a visual neuron responds to
What is the receptive field?
Researcher who used the Limulus eye to study encoding and lateral inhibition
Who is HK Hartline?
You are trying to determine what type of cell from the visual pathway you have. When stimulated, you observe a spike. What type of cell is this likely?
An RGC
Photoreceptors peripheral to the fovea that respond to low light
what are rods?
What are the 3 characteristics of lateral inhibition?
reciprocal (every ommatidium inhibits neighbors), graded (more intense stimuli = stronger effect), logarithmic
location of the retina corresponding to a particular part of the visual field
What is retinal eccentricity?
The channels that the researchers in Paper 4 were studying
What is rTRPV1 and sTRPA1?
You stimulate a photoreceptor and observe the cell the synapses with that photoreceptor. Following the stimulus, you observe depolarization. What type of cell is this?
On center bipolar
Have axons in optic nerve
What are retinal ganglion cells?
Fill in the blanks: In the dark, guanylate cyclase activity is ____, PDE activity is _______, and cGMP levels are ________
high, low, increasing (high)
Multiple receptors respond over different amplitude levels to help encode visual signals
What is range fractionation?
Briefly describe Limulus eye experiment for rate coding of light intensity
Shone light on one ommatidium and recorded the spike frequency of its axon extracellularly
You have a center ON bipolar cell and you provide a stimulus with a bright center and dim surround. What will you observe?
Increased bipolar cell activity (more depolarization)
Directly connects photoreceptor with RGC
what are bipolar cells?
You decide to replicate Hartline's study on the Limulus, but you inhibit transducin. What would you see on the recording?
no increase in spike frequency from base level (in dark)
Adjustment of a photoreceptor's sensitivity according to the background light level
What is adaptation?
In humans, how many photons (minimum) are needed to get visual sensation?
one
You have a spot of light moving from left to right. You delay input from a photoreceptor on the left and no delay from one on the right. These two photoreceptors feed into the same RGC. What will this setup cause?
The RGC will be directionally selective
Provide lateral inhibition and create antagonistic surround
What are horizontal cells?