Nervous Systems V

Pregunta	Respuesta
Photoreceptors are	Cells that absorb light
Invertebrate / verterbrate photoreceptors	Retinula cells Rods and Cones
Retinula cells	Have rhabdomere formed by Mv Light depolarises the cell
Rods and Cones	Opsin molecules stacks of modified cillia Light hyperpolarises the cell
Eye diagram	Cornea lens optic disc retina
Where are photoreceptors found/	In retina
Rod / cone diagram	Outer segment of modified cilium inner segment synaptic terminals
Comparing structure and function	Cones have shorter stacks, less opsin, less light sensitive Rods more discs = more opsin = remain active even at low level light
Vertebrate phototransduction in the dark	Na+ and Ca++ channels kept open by high cGMP PhotoR depolarises Transmitter released RECEPTOR ITSELF DOESN'T GENERATE AP
Vertebrate phototransduction in light	Light activates transducin to break cGMP to GMP Ion channels close, hyperpolarising the cell and reducing transmitter release
What are the 4 classes of photoR in humans?	Red/green/blue cones and rods
How would you compare their absorbance on a graph?	Relative absorbance (%) against wavelength (nm)
What colour don't rods absorb?	red
Show the visual pathway of light sensing in humans	Sensory R in retina Gnaglion cells synapse to thalamic nucleus Thalamic cell geos direct to 1' visual cortex Cross-over at optic chiasma
Where is colour processed in the 1' visual cortex?	V4
Where are dynamic movements processed?	V5
Visual processing in lower vertebrates	Reptiles, amphibians, and fish have rudimentary forebrains Reflex movement is processed in the optic tectum (midbrain)
Bird visual acuity	visual acuity in medial forea (side vision) is x2/3 that of humans
Invertebrate phototransduction in light	Light + 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
What are compound eyes made up of?	Photor, each with its own lens and colour cartridge
What is the cartridge known as?	Ommatidium
Diagram of ommatidium	Photor1-8 rhabdomeres pigment cells lens
What is special about compound eyes?	Can absorb light from all polarisation
Which rhabdomere have differing microvilli directions and why?	Outer 1-6, light from all directions sensed
Which rhabdomere are sensitive to polarisation?	7/8
Why do insects have this?	Because light is polarised in concentric circles around the sun so this aids navigation
Simple eyes	Ocelli
Use in flying insects	Triad of ocelli for horizon detection
What are the eyes of octopi and vertebrates an example of?	Convergent evolution

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	Creado por J yadonknow hace más de 6 años