Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Neurotoxicity ?
    ### Response:
    Neurotoxicity occurs when the exposure to natural or manmade toxic substances (neurotoxicants) alters the normal activity of the nervous system. This can eventually disrupt or even kill neurons, key cells that transmit and process signals in the brain and other parts of the nervous system.
    