Chapter 13: Synaptic Transmission in the Nervous System

Synaptic transmission forms the fundamental mechanism through which neurons communicate and coordinate activity throughout the nervous system. This chapter examines the molecular and cellular processes underlying neurotransmitter release, receptor binding, and signal transduction at the synapse. The discussion begins with the anatomy of the synapse, including the presynaptic terminal, synaptic cleft, and postsynaptic membrane, establishing the structural framework for chemical communication. The chapter details the synthesis, storage, and release of neurotransmitters, explaining how action potentials trigger calcium influx and the subsequent fusion of synaptic vesicles with the presynaptic membrane through the soluble NSF attachment protein receptor (SNARE) complex. Major neurotransmitter systems are analyzed, including glutamatergic excitatory transmission, GABAergic and glycinergic inhibitory transmission, and monoaminergic systems involving dopamine, serotonin, and norepinephrine. Receptor classification and function are explored, distinguishing between ionotropic receptors that directly gate ion channels and metabotropic receptors that activate intracellular signaling cascades through G proteins and second messengers. The chapter integrates temporal and spatial aspects of synaptic integration, examining how neurons sum excitatory and inhibitory postsynaptic potentials to determine whether an action potential will be generated. Synaptic plasticity mechanisms including long-term potentiation and long-term depression are discussed as cellular substrates of learning and memory. The chapter concludes by connecting synaptic dysfunction to neurological and psychiatric disorders such as epilepsy, schizophrenia, depression, and Parkinson's disease, demonstrating how disruptions in neurotransmission underlie clinical pathology and inform pharmacological intervention strategies.