Biol 109 - 14.docx - Bio 109 Intro to Physio Summer 2018 ●...

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Bio 109Intro to PhysioSummer 2018Spinal CordIf the spinal cord is severed there is loss of sensation from the skin and muscles aswell as paralysis, loss of the ability to voluntarily control musclesSpinal cord is divided into four regions: cervical, thoracic, lumbar, and sacralEach spinal region is subdivided into segments and each segment gives rise tobilateral pair of spinal nervesJust before spinal nerve joins the spinal cord it divides into two branches calledroots (figure 9-7)The dorsal root of is specialized to carry incoming sensory informationThe dorsal root ganglia, swelling found on the dorsal root justbefore they enter the cord, contain cell bodies of sensory neuronsVentral root carries information from the CNS to muscle and glandsThe cross section of the spinal cord has an H shaped core of gray matter and asurrounding rim of white matterSensory fibers from the dorsal roots synapse with interneurons in thedorsal horns of the gray matterDorsal horn cell bodies are organized into two distinct nuclei, onefor somatic information and one for visceral informationThe ventral horns of the gray matter contain cell bodies of motor neuronsthat carry efferent signals to muscles and glandsVentral horns are organized into somatic motor and autonomicnucleiEfferent fibers leave the spinal cord via the ventral rootAscending tracts take sensory information to the brainThey occupy the dorsal and external lateral portions of the spinal cordDescending tracts carry mostly efferent (motor) signals from the brain to the cordOccupy the ventral and interior later portions of the white matter

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