Dendrites in some neurons can branch profusely (large numbers of dendritic branches off the main shaft of a dendrite with their own branches are often collectively called dendritic trees), expanding the region of the neuron that can receive inputs from other neurons. The second main part of the neuron is the dendrites, the receivers of the neuron. The soma also contains the nucleus, where the genes and chromosomes (containing DNA) are located. These are involved in the basic metabolism of the cell. The soma or cell body contains organelles, common to all types of cells in the body. Various types of neurons are discussed below. Figure 5.1.4 shows this basic neuron anatomy. The cell membrane of a neuron has channels or "doors" for ions (electrically charged atoms) which can pass through the membrane when specific channels are opened for specific ions. The entire neuron is bounded by a cell membrane, the neural membrane. As noted above, neurons have three major structural parts - the soma or cell body, the axon (carries the neuron's output), and the dendrites (the "receivers" of the neuron). To understand neuron function, it is important to be familiar with the anatomy involved. Cajal and Golgi shared the Nobel Prize for Medicine in 1906 for their combined contribution to the advancement of science and our understanding of the structure of the nervous system. Based on his observation of Golgi-stained tissue, Cajal suggested neurons were distinguishable processing units rather than part of a continuous network of nerves, as had been previously believed. This significantly enhanced our appreciation of the intricate networks their processes form. These qualities of the Golgi stain allowed the pioneering neuroanatomist Santiago Ramon y Cajal to examine the full anatomical structure of individual neurons for the first time. A more notable characteristic of a Golgi stain is that it only stains approximately 1–2% of neurons ( Pasternak
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