Physiology of the Visual System Flashcards
How does the eye achieve more curvature for accommodation?
Ciliary muscle contracts while the suspensory ligaments loosen.
How does the eye achieve less curvature for far vision?
Ciliary muscle relax while the suspensory ligaments tighten
How does the eye achieve the near accommodation response?
Contract ciliary muscles, convergence of eyes to a point of focus and constriction of the pupil to let less light come in.
What are the five neuron types in the retina?
Receptor Cells (rods and cones), Bipolar cells, Ganglion Cells, Horizontal cells and Amacrine Cells.
Where is the density of the cones the highest in the eye?
Center of the fovea
When is glutamate released at the highest from rods and cones?
In darkness.
How are bipolar cells activated?
By photon stimulation of photoreceptors on the cone cell, causing Glutamate release to decrease.
Describe an On-Center bipolar cell.
Bulls-eye like activation pattern, activation in the center of the cell will cause depolarization of the cell, in the periphery will cause hyperpolarization.
Explain what happens to the On-Center cell during dark conditions.
Glutamate activates Gi GPCR, resulting in a decrease of cation influx, hyperpolarizing the cell.
Explain what happens to the On-Center cell during bright conditions.
Photons cause less glutamate to be around, so there is less Gi signalling, resulting in an increase of cations into the cell, causing depolarization.
Explain what happens to the Off-Center cell during dark conditions.
Glutamate activates AMPA receptors, resulting in a cation influx and depolarizing the cell.
Explain what happens to the Off-Center cell during bright conditions.
Less Glutamate is around, so there is less AMPA activaton, decreasing cation influx and hyperpolarizing cell.
Explain what happens to ganglion cells when the bipolar cell is activated.
Activated bipolar cell will release glutamate, causing depolarization to occur and eventually an action potential.
Explain how activation of rod photoreceptors affect On-Center bipolar cells.
Rod bipolar cell will conect to a rod amacrine cell, and release glycine or GABA
What are the functions of the Lateral Geniculate Body? (4)
Control motions of eyes to converge on a target. control focus of eyes for distance, determine relative position, detect movement relative to an object.
What layers of the primary visual cortex receive input from the LGB?
Layer IV
What layers are the main output layers of the primary visual cortex?
Layers V and VI
What are ocular dominance columns in the primary visual cortex?
Columns that span all VI cortex layers that preferentially respond to one eye over the other.
What are orientation columns in the primary visual cortex?
Columns that are excited by different visual line stimuli of different angles. Some are more able to see vertical lines, others horizontal, etc.
What is the function of the Blobs of the primary visual cortex?
Absorption of information from the cones that are specific for either the Red, Green or Blue cones.
What is the major job of V1 in the visual cortex?
To identify edges and contours.
What is the major job of V2 in the visual cortex?
Depth perception.
What is the major function of V3a in the visual cortex?
Identification of motion.
What is the major function of V4 in the visual cortex?
Processing of color inputs.
