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Nervous Systems V
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- 1Photoreceptors areCells that absorb light
- 2Invertebrate / verterbrate photoreceptorsRetinula cells
Rods and Cones - 3Retinula cellsHave rhabdomere formed by Mv
Light depolarises the cell - 4Rods and ConesOpsin molecules
stacks of modified cillia
Light hyperpolarises the cell - 5Eye diagramCornea
lens
optic disc
retina - 6Where are photoreceptors found/In retina
- 7Rod / cone diagramOuter segment of modified cilium
inner segment
synaptic terminals - 8Comparing structure and functionCones have shorter stacks, less opsin, less light sensitive
Rods more discs = more opsin = remain active even at low level light - 9Vertebrate phototransduction in the darkNa+ and Ca++ channels kept open by high cGMP
PhotoR depolarises
Transmitter released
RECEPTOR ITSELF DOESN'T GENERATE AP - 10Vertebrate phototransduction in lightLight activates transducin to break cGMP to GMP
Ion channels close, hyperpolarising the cell and reducing transmitter release - 11What are the 4 classes of photoR in humans?Red/green/blue cones and rods
- 12How would you compare their absorbance on a graph?Relative absorbance (%) against wavelength (nm)
- 13What colour don't rods absorb?red
- 14Show the visual pathway of light sensing in humansSensory R in retina
Gnaglion cells synapse to thalamic nucleus
Thalamic cell geos direct to 1' visual cortex
Cross-over at optic chiasma - 15Where is colour processed in the 1' visual cortex?V4
- 16Where are dynamic movements processed?V5
- 17Visual processing in lower vertebratesReptiles, amphibians, and fish have rudimentary forebrains
Reflex movement is processed in the optic tectum (midbrain) - 18Bird visual acuityvisual acuity in medial forea (side vision) is x2/3 that of humans
- 19Invertebrate phototransduction in lightLight + in opsin, + PLC -> PIP2 -> DAG + IP3
This opens ion channels in membrane causing the photorecetor to depolarise and release histamine, but don't generate AP - 20What are compound eyes made up of?Photor, each with its own lens and colour cartridge
- 21What is the cartridge known as?Ommatidium
- 22Diagram of ommatidiumPhotor1-8
rhabdomeres
pigment cells
lens - 23What is special about compound eyes?Can absorb light from all polarisation
- 24Which rhabdomere have differing microvilli directions and why?Outer 1-6, light from all directions sensed
- 25Which rhabdomere are sensitive to polarisation?7/8
- 26Why do insects have this?Because light is polarised in concentric circles around the sun so this aids navigation
- 27Simple eyesOcelli
- 28Use in flying insectsTriad of ocelli for horizon detection
- 29What are the eyes of octopi and vertebrates an example of?Convergent evolution
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- El usuario ha eliminado su información de asignaturas Fichas sobre Nervous Systems V, creado por Usuario eliminado el 07/05/2018.
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- Creado por J yadonknow · 7 may 2018
- Copiado por J yadonknow · 7 may 2018
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