Chemical communication is carried out between neurons by substances called

Chemical communication is carried out between neurons by substances called neurotransmitters. The main function of neurotransmitters is to transmit signals from one neuron to another one which is usually called 'target cell'. These chemical messengers are received by receptors on that target cells. There is no exact number of neurotransmitters, but you just must know that there was about 100 that are already known.

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Where is the graph ?