Fichas
Vision
Fichas del conjunto (25)
- 1Macula- In fovea
- Allows us to see centrally
- Critical for high resolution - 2What limits visual acuity (detail)?- Pupil size
- Refractive error (eye shape): short sided/long sided - 3Rods- Night vision (sensitive to light)
- 95% of our eyes
- One type only
- No colour vision
- Highest density slightly off centre - 4Cones- Day vision
- Colour vision as 3 types: Red, Green, Blue
- 5% of our eyes
- Highest density in fovea (centre) - 5Function of Photoreceptors- Contain photopigments that are activated by light. Rhodopsin in rods and cone-opsin in cones binds with vit A.
- Kink changes which allows conversion of light into retinal signal.
- Respond to light with changed in membrane potential not AP. - 6Photoreceptors in the darkNa channels help open by cGMP, causing continuous influx, causing depolarisation of cell
- 7Photoreceptors in the lightcGMP breaks down to GMP, influx of Na ceases, cell is hyper-polarised.
- 8Phototransduction-Light into neural signal
- Light activates rhodopsin- rhodopsin activates transducin- activates PDE (enzyme)- breaks down cGMP- closure of channels- hyper polarisation - 9Retinal Through PathwayPhotoreceptors - Bipolar Cells- Ganglion Cells
- Modulated by Horizontal Cells in outer retina
- Modulated by Amacrine Cells in inner retina - 10How many neuronal types in the retina?6 types
- Rods, Cones, Horizontal Cells, Bipolar Cells, Amacrine Cells - 11Receptive field of ganglion cellArea of retina that when stimulated with light changes the cells membrane potential
- 12How do ganglion cells respond to light?Increasing or decreasing their action potential firing rate or transient or sustained response.
- 13Horizontal CellsLateral inhibitor by releasing GABA neurotransmitter.
- 14Amacrine CellsLateral inhibition by releasing glycine and GABA neurotransmitters. Axon-less.
- 15M (magnocellular, parasol) Cells- Type of ganglion cell (neuron)
- Large receptive field
- Large in size
- Provides motion detection info - 16P (parvocellular, midget) Cells- Type of ganglion cell
- Small in size
- More numerous
- Visual acuity (detail), colour vision - 17Ganglion Cells- M and P Cells
- Output targets are many brain regions (majority target the lateral geniculate nucleus (thalamus)
- Transmit visual information to the brain - 18Visual PathwayRetina- Optic Nerve (axons of ganglion cells form the OP)- Lateral Geniculate Nucleus (Thalamus): where GCs synapse- LGN neurons send axons down Optic Radiations- these target Visual Cortex
- Nasal parts info goes to the opposite side LGN
- Temporal parts info goes to the same side. - 19Optic Chiasm- When the fibres from the left and right optic nerves combine (visual
- At the base of the brain - 20Lateral Geniculate Nucleus- 6 layers
- Contained M and P Cells
- M Cells (Layers 1,2) receive input from M cells
- P Cells (Layers 3-6) receive input from P Cells.
- No mixing of info from each eye (3 each) - 21Optic RadiationsWhite matter tracts from LGN to primary visual cortex (occipital lobe).
- 22Primary Visual Cortex- Occipital Lobe
- LGN neurons terminate here
- Each half of the visual field is represented on the contralateral (opposite) visual cortex.
- Mixing now occurs.
- Most posterior part is for central vision - 23Corticol neuronsOrientation Selectivity: Neurons respond better to bars moving in particular orientation (stimulus orientation= diagonal/vertical/horizontal). - different colours have different bars of light.
- 24Ventral StreamV1, V2, V4- runs down ventral part of the occipital lobe
- 25Area IT (inferior temporal)- Neurons respond to a wide variety of shapes and colours
- Important for visual memory and perception
- Important for perception of faces.
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- (Sensory System) Neuroscience Fichas sobre Vision, creado por Anokhi Patel el 22/05/2018.
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- Anokhi Patel
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