File:Neuroanatomy fig4.jpg

Electron microscopic picture of two synapses from the cerebral cortex of the mouse. Membranes of cellular and subcellular structures are stained with osmium. The arrows point to the thickening that characterizes the postsynaptic membrane. In A) the postsynaptic element is a dendritic spine (S); in B) it is a dendrite (D), cut transversally and showing the regular arrangement of microtubuli. In the axonal part, (Ax) synaptic vesicles can be seen (V). The synapse in A) is excitatory, recognizable by the thick postsynaptic thickening and the round vesicles. The synapse in B) has a thin postsynaptic thickening and more elongated vesicles - features that characterize inhibitory synapses in the cerebral cortex. Some mitochondria are marked (m).