Axon to dendrite to cellbody11/25/2023 ![]() Melanin pigments are found in the neuron of the substantia nigra in the midbrain. ![]() Microfilaments and microtubules are numerous and arranged in parallel bundles throughout the perikaryon. Mitochondria are abundant, ovoid or thread like, and randomly distributed. The Golgi is diffuse and located mainly around the nucleus. In cases of neuronal injury, the perikaryon swells, the nucleus becomes eccentric and Nissl bodies disappear except peripherally (chromatolysis ). The great abundance of free ribosomes and polysomes that are located in the spaces between the rER cisternae is required to synthesis cytoplasmic protiens that continuously flow to replace proteins used up in metabolism. These basophilic masses are called Nissl bodies or chromophilic substance and are especially prominent in large neurons. The cytoplasm of the nerve cells contains large aggregations of rER that appear as deeply basophilic masses scattered throughout the different cytoplasmic regions. The female sex chromatin (Barr body) is usually evident either close to the nucleolus (cat) or the nuclear envelope (human being). With EM, a small amount of peripheral chromatin can be seen on the inner aspects of nuclear envelop. The chromatin is completely dispersed and the nucleolus is prominent (owl’s eye). The nucleus is large, spherical or ovoid and usually centrally located within the perikaryon, but in autonomic neurons it has an eccentric position. It includes the nucleus and it’s surrounding cytoplasm. They are located in the gray matter of the central nervous system, eye (rods and cones), ears (organ of Corti), olfactory mucosa, and ganglia. ![]() Each neuron is composed of cell body (perikaryon) and cell processes. It is the structural and functional unit of the nervous tissue that is specialized in excitability and conductivity. It is made up of nerve cells (neurons) and different types of supporting cells collectively known as neuroglia. The nervous tissue functions as a communication network to receive stimuli from both internal and external environment (exteroception) and subsequent transmission of signals or information (interoception) throughout the body or effector organs (muscles or glands).
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