Exam 2- Vision Flashcards
Be able to explain the 4Rs.
Reweighting- A synapses becomes stronger by releasing more neurotransmitters and increasing the number of receptors
Reconnection- Synapses can be both created and eliminated
Rewiring- Branches of axons and dendrites are able to grow and retract
Regeneration- In adulthood, neurons are created and eliminated
Be able to explain the research studies in hamsters and kittens that showed how visual deprivation changes the cortex.
Kittens- After the kittens have their vision blocked in one eye, the neurons of the primary visual cortex (V1), have been altered. Depriving one eye causes axons to retract its pathways and creates new pathways in the other eye. The changes are reversible while as young kitten but irreversible during adulthood.
* Shows rewiring of the brain
* Suggests that we are not born with the ability to see
Hamsters- After their visual cortex was cut, the visual input of hamsters were sent to the auditory cortex and research showed that the auditory cortex responded to visual stimulation
* Shows plasticity of the brain
Be able to explain the four steps involved in brain growth.
1) Neurons are created through division of progenitor cells
2) Migrate to proper places in brain
3) Extend branches (“wiring” of the brain)
4) Make connections (through synapses)
Review the neuroscience techniques that were discussed in these readings
Golgi’s Method of Electron Staining- only marks a fraction of neurons which allows scientists to visualize neurons more easily
Electron microscopy- allows scientists to see the gaps between neurons at synapses
Serial block face scanning electron microscopy- creates a stack of 2D images without distortion
Automated tape collecting ultramicrotome- collects thin brain slices on a plastic tape, which eliminates human error
Review the difference between AI and IA.
AI (Artificial Intelligence)- machines that intelligent enough to solve problems without people
IA (Intelligence Amplification)- machines that make people more intelligent by working together to solve problems
Make sure that you can explain how vision was restored in a man with retinitis pigmentosa. In your explanation, you should be able to explain what happens to cause the loss of vision in patients with retinitis pigmentosa.
Researchers inject a virus to deliver light-sensitive proteins into the RGCs, allowing them to detect images directly and avoiding the damaged photoreceptors. Goggles are then used to convert light into dots. When light from these dots enter a person’s eye, it activates the proteins and causes the RGCs to send a signal to the brain.
Review the roles of optogenetics, the virus, retinal ganglion cells, the goggles, etc., in this treatment.
Retinitis pigmentosa- a degenerative disease that kills off the eye’s photoreceptors
Photoreceptors detect light and send electrical signals to retinal ganglion cells (RGCs)
Optogenetics- uses flashes of light to control gene expression and neuron firing
Treatment for pain, blindness, and brain disorders
Virus- delivers light-sensitive proteins to RGCs
Retinal Ganglion Cells (RGCs)- transmit signals to the brain
Goggles- uses dots to activate proteins as light enters the eye, and causes RGCs to send signal to brain
Be able to describe the visual deficits of the man who mistook his wife for a hat. Review your answers to the case study questions.
The man could not see the whole picture, but can see details
He could not recognize faces of people and saw faces when there were no faces
He thought the fire hydrant and parking meter were children
When shown a cover of the dunes, he saw nonexistent things
* The problem was with how the brain processes the information (right hemisphere mainly)
Review the general anatomy of the eye: where would you find the cornea, lens, retina, optic disc, blind spot, optic nerve, photoreceptors, rods, cones, bipolar neurons, ganglion cells, and the fovea?
Photoreceptors- detects light
Rods- dim light, gray tone contrasts (rectangular)
Cones- color, only in brighter light (conical)
Bipolar neurons
Ganglion cells
Optic nerves
Fovea- center of our gaze that consist many cones, no rods
Optic disc- area that contain no receptors and therefore cannot process visual info, making it a blind spot
What are astigmatism, hyperopia, and myopia?
Astigmatism- vision is blurry and distorted
Hyperopia- farsightedness
Myopia- nearsightedness
When are photoreceptors most active: in the dark or in the light?
Photoreceptors are more active in the dark
-Optic nerve is not active because it inhibits bipolar and ganglion cells
In the light, the opposite takes effect
How is color information processed in photoreceptors and in the opponent ganglion cells?
Photoreceptors- light is absorbed by cone photoreceptors that respond to blue, green, red wavelengths
Ganglion cells- respond to specific types of color in opposition to each other (red-green, blue-yellow)
* One will be excited, the other will be inhibited (ex. red is excited, green is inhibited)
* Why we see certain colors and some colors we can’t see
What is the pathway of visual signals from the eye to the brain?
Light enters the eye (cornea, then pupil, then lens), visual signals gets sent to the photoreceptors, to bipolar neurons, to opponent ganglion cells, then to optic nerve, then to brain
What is a visual field? What are the functions of the optic chiasm, lateral geniculate nucleus of the thalamus, superior colliculi, and occipital lobes? Be able to explain how a patient’s vision might be affected if there was damage to any of these specific areas.
Visual field- area to which you can see (center and peripheral)
Optic chiasm- where optic nerve fibers cross
1) Superior colliculi- part of the midbrain that control visual reflexes
2) Lateral Geniculate Nucleus of the Thalamus- relays sensory information
3) Visual cortex- processes visual information, located in the occipital lobes
What was shown by recordings taken from neurons in the visual cortex of a cat?
Researchers (Hubel & Wiesel) presented light stimuli to a cat and recorded the sounds of neurons firing (action potential) in response to the light in the cat’s visual cortex.
The cells responds when a bar of light is put on the area marked by X’s
Triangle = OFF areas and X’s = ON areas
Different cells respond to different shapes, light or darkness, or movement
