Neurotransmitters are chemical messengers released by neurons throughout the nervous system, transmitting an impulse from one cell to the next. Neurotransmitters are made in the brain, but also by the bacteria in our gut. Neurotransmitters are either inhibitory (calming), excitatory (stimulating) or modulating (regulating), and this determines the effect they have on the cell they are communicating with.(2017). Neurotransmitter. [online] Encyclopaedia Britannica. Available at: https://www.britannica.com/science/neurotransmitter [Accessed 19 Nov. 2018].Queensland Brain Institute. (n.d.). What are neurotransmitters? [online] Available at: https://qbi.uq.edu.au/brain/brain-physiology/what-are-neurotransmitters [Accessed 19 Nov. 2018]. Carpenter, S. (2012). That gut feeling. American Psychological Association: Monitor On Psychology, [online] 43(8), p.50. Available at: https://www.apa.org/monitor/2012/09/gut-feeling.aspx [Accessed 19 Nov. 2018].