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    for the generation of the generator potential, do Na ions get pumped out the inner segement by active transport and diffure into the outer segment or is it the other way round :confused:
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    If it is the same as an action potential, then sodium ions move into the axon membrane
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    OK, here ya go. It's the other way round from a normal action potential - the membrane is hyperpolarised not depolarised and Na+ ion channles close not open.

    Light falls on the rhodopsin in the rod cells. (rhodopsin = opsin + retinal).
    The light causes retinal to change shape (position of molecules in space actually change, not the chemical structure, but i think you only need to know that if you're doing chemistry) from a cis to a trans isomer.
    The retinal can no longer form bonds with opsin so the rhodopsin 'splits' (bleaching).
    This causes Na+ channels to close which hyperpolarises the membrane creating a generator potential (note this is a different way round - in most other receptors Na+ channels open to cause a GP).
    If the stimulus is great enough (all or nothing law) then it stops vesicles fusing with the pre-synaptic membrane.
    The vesicles contain an inhibiting neurotransmitter which prevent an action potential being created across the bipolar cell membrane.
    When the neurotransmitter is not released, an action potential is created in the bipolar cells (-> ganglion cells which make up the optic nerve).
    Be aware that this is the wrong way round compare to a normal neuron - the neurotransmitter is inhibitory.

    PM me if you need any more help...
    skevvybritt x
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    u never mensioned anythin about cones, rods, about rods sensitive to low light intensities, cones with red, blue and green and form different colours due to trichromatic theory..rods containing rhodopsin...cones with iodopsin...several rods connected to one bipolar cell whereas one cone with one bipolar cell so are more sensitive and give more accurate sight
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    (Original post by DmAsTeR)
    u never mensioned anythin about cones, rods, about rods sensitive to low light intensities, cones with red, blue and green and form different colours due to trichromatic theory..rods containing rhodopsin...cones with iodopsin...several rods connected to one bipolar cell whereas one cone with one bipolar cell so are more sensitive and give more accurate sight
    Um, maybe because that wouldn't be relevant to the q the thread-starter asked?
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    the last sentence was relevant
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    (Original post by DmAsTeR)
    the last sentence was relevant
    Not really. It explains why cones provide visual acuity, but not how the generator potential is made.
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    (Original post by DmAsTeR)
    u never mensioned anythin about cones, rods, about rods sensitive to low light intensities, cones with red, blue and green and form different colours due to trichromatic theory..rods containing rhodopsin...cones with iodopsin...several rods connected to one bipolar cell whereas one cone with one bipolar cell so are more sensitive and give more accurate sight
    I'm afraid that isn't covered in my syllabus so I don't know anything about it.

    Feel free to add on, if you feel that would be helpful to the thread starter, although tbh I thought I'd gone a bit beyond what I needed to do with that explanation.
 
 
 
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