This lecture explains the diffusive component of synaptic transmission, where neurotransmitters released from a presynaptic bouton can also bind to receptors in the extracellular space, influencing brain function through volume transmission. The neurotransmitters glutamate and GABA have both one-to-one and volume transmission components, while other neurotransmitters rely solely on volume transmission. Different forms of synaptic transmission are discussed, including fast point-to-point chemical transmission and slower biochemical signaling cascades.