![]() ![]() Oligodendrocyte cells produce myelin in the central nervous system (brain and spinal cord) while the Schwann cell produces myelin in the peripheral nervous system ( ). Microglia protect the nervous system against infection but are not nervous tissue because they are related to macrophages. The astrocytes have many functions, including regulation of ion concentration in the intercellular space, uptake and/or breakdown of some neurotransmitters, and formation of the blood-brain barrier, the membrane that separates the circulatory system from the brain. Astrocyte cells, named for their distinctive star shape, are abundant in the central nervous system. Recent research is shedding light on the more complex role of neuroglia in the function of the brain and nervous system. The word “glia” comes from the Greek word for glue. The second class of neural cells comprises the neuroglia or glial cells, which have been characterized as having a simple support role. If enough neurotransmitters are released at the synapse to stimulate the next neuron or target, a response is generated. Dendritic spines play a crucial role in memory and learning through occurrence of long-term potentiation (LTP), which is thought to be the cellular level of learning and memory. When a neuron is sufficiently stimulated, it generates an action potential that propagates down the axon towards the synapse. Bipolar neurons possess a single dendrite and axon with the cell body, while unipolar neurons have only a single process extending out from the cell body, which divides into a functional dendrite and into a functional axon. Neurons categorized as multipolar neurons have several dendrites and a single prominent axon. The synapse is the gap between nerve cells, or between a nerve cell and its target, for example, a muscle or a gland, across which the impulse is transmitted by chemical compounds known as neurotransmitters. A long “tail,” the axon, extends from the neuron body and can be wrapped in an insulating layer known as myelin, which is formed by accessory cells. Dendrites branch off the cell body and appear as thin extensions. The cell body includes most of the cytoplasm, the organelles, and the nucleus. Neurons display distinctive morphology, well suited to their role as conducting cells, with three main parts. Follow this link to learn more about nervous tissue.
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