1 Dendrite structure

Dendrites are extensions of the cell body of the neuron specialized for receiving and processing the vast majority of excitatory synaptic inputs. Dendrites exhibit enormously diverse forms. In many cases the shape of the dendritic arbor can be related to the mode of connectivity between neurons, with dendrites often ramifying in characteristic spatial domains where they receive specific inputs. At the ultrastructural level, dendrites are distinct from axons and astroglia processes, having a characteristic composition of subcellular organelles. Synapses occur directly on the shaft of some dendrites, but other dendrites have specialized enlargements and protrusions to receive synaptic input. These synaptic specializations also occur in many different forms. The use of serial electron microscopy to obtain detailed quantitative data on these structures has shown that different synaptic specializations have different intracellular organelles and synaptic compositions. Understanding the structural diversity of both dendritic arbors and synaptic specializations will be essential for understanding the intricacies of dendritic function and the contribution dendrites make to mental processes.