Category B - full version without watermark 1024x576 (check terms and conditions at www.teledesign.de) The embed version with watermark is free of charge. - Description: The brain is the "command center" of the human body. It controls the basic functions of our bodies, our movements, and our thoughts and emotions. Two transmitters implicated in depression are serotonin and norepinephrine. It is unknown whether changes in levels of neurotransmitters cause the development of depression or depression causes changes in neurotransmitters.