![]() ![]() From the spinal cord emanate the spinal nerve roots. The spinal cord is arranged with outer white matter and inner grey matter with neurons such as the anterior horn cells. There are three layers comprising the cerebellar cortex. The cerebellum is involved with controlling and fine-tuning movement. The hippocampus is also involved in processing short term memories. ![]() Histologically, the cortex of the cerebral hemispheres can be categorized as "neocortex" with six layers, considered more developed, and the "paleocortex" with three layers, seen in central structures controlling more primitive reflexive, emotional functions of the limbic system, such as the hippocampus. Grossly, structures such as the cerebral cortex have many neurons and appear grey, the so-called "grey matter." Regions of the brain that are composed primarily of fiber tracts making connections appear lighter, the so-called "white matter". The cerebral hemispheres can be further categorized by structure and function. The brain is composed of the basic units of the cerebral hemispheres, brainstem, and cerebellum. These cells form the substance of the brain, spinal cord, and peripheral nervous system. Myelinated axons conduct nerve impulses faster. Myelin is high in lipid and serves the same purpose as insulation around electrical wires. Larger neurons are covered in a myelin sheath. Schwann cells: these cells provide the myelin that covers neurons in the peripheral nervous system. However, when injury occurs, they become more numerous Microglia: these cells are part of the mononuclear phagocyte system of fixed macrophages in tissues. A single oligodendrocyte can provide myelin for as many as 40 neurons. They produce the myelin that surrounds the axons of myelinated neurons of the CNS. Oligodendroglia: the oligodendroglial cells are small round cells that are most prominent in white matter. The cytoplasm of astrocytes contains intermediate filaments that are composed of glial fibrillary acidic protein (GFAP) that serves to identify these cells. At least one process either extends to and surrounds a capillary or extends to the overlying pia of the brain. These include:Īstrocytes: these cells in the brain have a small, round nucleus and many very thin processes that radiate from them. There are a variety of cells which support neuronal function. Cells of the Nervous System - Glial Cells Interneurons: these are connectors between neurons in the CNS. Sensory neurons: these afferent neurons conduct impulses from sensory stimuli to the central nervous system. ![]() Motor neurons: these efferent neurons extend distally to send nerve impulses to muscles for voluntary movement. Some axons are covered in a sheath of myelin. Axons contain organelles and neurofilaments. At the distal end there is a terminal arborization with synapses to other neurons. Most neurons have a single axon, though some can have more than one. Īxon: a long process that conducts impulses (action potentials) away from the cell body.They contain some organelles and many neurofilaments. ĭendrites: these small arborizing processes receive almost all of the input (nerver impulses).The cell body is receptive to input, but only a minority of impulses arrive directly onto the cell body. There are neurofilaments that can occur singly or in clusters. The cytoplasm contains rough endoplasmic reticulum grouped to form the Nissl substance. In general, they have the following components:Ĭell body: the nucleus and cytoplasm containing organelles are contained here. Neurons come in a variety of shapes and sizes. The major function of the nervous system is provided by neurons. The neural crest cells migrate to give rise to most of the peripheral nervous system. From the anterior neural tube additional folding and development produces the complex regions of the brain. Embryologically, the central nervous system is derived from the neural plate which closes to form the neural tube. The two major divisions of the nervous system are the central nervous system (CNS), consisting of the brain and spinal cord, and the peripheral nervous system (PNS) consisting of the peripheral nerves, nerve receptor endings, and ganglia distributed throughout the body. Nervous System Nervous System Return to the Histology Tutorial menu. ![]()
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