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Anatomy Tutorial: Nervous System Overview

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mostly review from introductory bio but just in case \({\bf{Divisions~of~the~Nervous~System:}}\) nervous system has two main divisions, the central nervous system (CNS) and the peripheral nervous system (PNS) > CNS: the brain and spinal cord - processes/coordinates sensory input + motor output - controls higher functions - originates as hollow tube --> expands into central canal and ventricles > PNS: all nerves outside the CNS - two divisions, afferent and efferent - afferent: sends sensory information to CNS; begins with receptors - efferent: sends motor commands to muscles/glands; ends with effectors \({\bf{Somatic~vs~Visceral:}}\) both afferent and efferent divisions contain these two sub-divisions > afferent: contains somatic sensory receptors (skeletal muscles, joints, skin) + visceral sensory receptors (non-skeletal muscles, glands, organs) > efferent: somatic nervous system (voluntary contractions) + autonomic nervous system (glands, non-skeletal muscle activity)

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|dw:1539571830850:dw| basic components of the neuron

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\({\bf{Neuroglia:}}\) 6 types to remember, 4 for the CNS and 2 for the PNS \({\bf{CNS~Neuroglia:}}\) astrocytes, oligodendrocytes, microglia, ependymal cells general functions: support neurons, supply nutrients, destroy pathogens, remove dead/damaged neurons \({\bf{Astrocytes:}}\) - largest, most numerous - contain pedicels that increase SA for nutrient exchange - encloses the neuron - maintains the blood-brain barrier - microfilment structural network - aid in repair and development of neurons \({\bf{Oligodendrocytes:}}\) - similar in structure to astrocytes but the cytoplasmic extensions are shorter, are generally smaller - form the myelin sheath around axons --> increases speed of information - internodes: regions of axon surrounded in myelin - myelin sheath gaps/nodes of ranvier: places where there is no myelin > white vs gray matter: myelinated axons vs. non-myelinated axons, dendrites, cell bodies, etc.

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\({\bf{Microglia:}}\) - the smallest and usu. the least populous but their populations increase in response to infection/injury - their stem cells are located in bone marrow - phagocytosis of waste products \({\bf{Ependymal~Cells:}}\) - line the ventricles of brain/spinal cord - cuboidal/columnar - branches that contact other neuroglia - in adults, ciliated to promote movement of CSF

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\({\bf{PNS~Neuroglia:}}\) form clusters (ganglia), isolate neurons in the PNS from the surrounding environment. 2 types, satellite + schwann \({\bf{Satellite:}}\) - surrounds neuron cell bodies - regulates nutrient exchange and waste product removal \({\bf{Schwann:}}\) - covers every peripheral axon, providing neurolemma

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Adapted from Human Anatomy, Martini, et. al. 9th edition

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