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Is there a connection between brain weight and intelligence? I don't agree with Mike, look at animals that are bigger than us. Women are usually smaller than men, does that mean they're less intelligent? A good explanation has more to do with the complexity of the brain; the connections between neurons and nuclei of the brain. Our brain is more complex compared to other species.

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Acetylcholine is not a biogenic amine- true or false, if false, why? I think it's (also) called a monoamine, just like serotonin and histamine. Adrenaline(epi.), noradrenaline(norepi.), dopa and dopamine are called catecholamines. Catecholamines are all made in the adrenal medulla. (Maybe biogenic amine means the same as monoamine or is a groupname)

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What is the differences between Lead Vector and Cardiac Vector? How is Lead Vector being used to measure ECG Signal? The (moving) heart vector represents the total electrical activity of the heart. Each ECG lead (I, II, III, etc.) is associated with a lead vector. So projection of the heart vector on one of the lead vectors gives the ECG amplitude(signal) in that ECG lead.