The Chamorro people of Guam eat flying foxes, a type of bat, as part of their diet. The photograph shows a flying fox. (Source: © H Lansdown/Alamy Stock Photo) Scientists in Guam suggested there was a link between the diet of these people and the high incidence of the neuro-degenerative disease amyotrophic lateral sclerosis (ALS) in their population. Neurotoxins can affect the potential differences generated across the membranes of motor neurones. (i) Draw a myelinated motor neurone and label two structures. (3) (ii) A different neurotoxin called tetrodotoxin inhibits the transmission of nerve impulses along axons. In an experiment, axons of motor neurones were stimulated in the absence of tetrodotoxin and in the presence of tetrodotoxin. The graphs show the potential differences obtained in this experiment. Explain how tetrodotoxin inhibits the transmission of a nerve impulse along the axon. (3) ................................................................................................................................................................................................................................................................................ ................................................................................................................................................................................................................................................................................ ................................................................................................................................................................................................................................................................................ ................................................................................................................................................................................................................................................................................ ................................................................................................................................................................................................................................................................................ ................................................................................................................................................................................................................................................................................ ................................................................................................................................................................................................................................................................................ ................................................................................................................................................................................................................................................................................ ................................................................................................................................................................................................................................................................................

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