Nervous tissue is made of specialized excitable cells termed neurons and support cells termed glia. We usually think about nervous tissue as being almost exclusive to neurons, there are within the body many more of the glial cells than there are neurons. Neurons are specialized cells that are differentiated and specialized from columnar epithelial cells that function to transmit electrical signals between cells and tissues. While glial cells are a hoist of various types of cells that support the function and “health” of the neurons. The key glial cells are the myelinating cells (Schwann and oligodendrocytes) that support and insult the axon of the neuron, and the astrocytes, microglia and oligioglia that support the health of the neuron via metabolic activities or functioning as immune like cells. The function of the neuron is to transmit membrane potential impulses to coordinate activity and integrate information for cognitive response to stimuli. Just like muscle tissue, nerve tissues are excitable, irritable and show plasticity to changing stimuli and release chemicals (neurotransmitters) in response to stimuli.
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Neurons are unique cells that are amitotic (they don’t divide once mature), aerobic obligated (they need constant blood flow and gas exchange to survive), and have an energy metabolism that is almost entirely dependent on glucose (this is why we need at least 120 grams of glucose in a day). Anatomically, they are classified by shape and by function relative to that shape and number of axon projections. With the identification being unipolar (one axonal projection), bipolar (two axonal projections), or multipolar (multiple axonal projections). Additionally, each of these types of neurons can also be classified by function as being afferent (transmit impulses to the central nervous system), efferent (transmit impulses to the peripheral target tissues), or interneuron (transmit impulses between neurons). The neuron with glial cells and connective tissue build together to form the nerve that is typically imagined when discussing the nervous tissue. There are secondary cells involved with the nervous tissue identified as separate special cells. These cells that are involved with sensation and release neurotransmitters but do not convey electrical impulses along an axon.