The nervous system sends messages from nerve endings to the brain and from the brain to cells, tissues, and organs. Cells of the nervous system sometimes secrete chemical messengers instead of neurotransmitters. These specialized nervous system cells are called neurosecretory cells, and they produce neurosecretions. Every nerve cells are long, thin cylinders along which electrical disturbances (nerve impulses) travel. the cell membrane of a typical nerve cell consists of an inner and an outer wall separated by a distance of 0.10 μm and the electric field within the cell membrane is 7.0×105n/c.
2)
This is because insulin allows the glucose to be travelled to the cells and liver for respiration
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Answer:
Because they don't have fertilizer.
Explanation:
Well, if this was a long time ago, then farmers did not have fertilizer. So, there are bacteria on the roots of plants that convert nitrogen into a usable form. It's very important for growing, and when farmers harvest the crop, not much of the nitrogen is returned to the land, so it is not as fertile. Fertilizer is largely consisted of nitrogen, so that is why farmers use fertilizers today. But "a long time ago," farmers did not have fertilizer.
It should be 3! That is the only logical answer to the question...
