Jeff and Paul attempt to walk us through the complicated mechanisms through which signals are sent to and received by brain cells. After a general introduction regarding the different kinds of neurotransmitters (and Jeff promising to talk about dopamine and failing to deliver), the boys chat about the electrical and chemical events that trigger the release of synaptic vesicles at the junction between two brain cells: the synapse. Jeff and Paul then discuss the mechanism through which SSRIs (selective serotonin reuptake inhibitors), a commonly prescribed antidepressant, relieve depression and anxiety.