Somatosensory - Spinal Cord Neurons of the Cord Afferent...

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Spinal Cord Neurons of the Cord Afferent neurons sensory located outside of the cord (dorsal root ganglia) receive information from the sensory receptors and sends that information toward the CNS Efferent neurons motor neurons located in ventral horn receives info form the CNS and sends it to the muscles Interneurons connects afferent pathways to efferent sends info to brain are involved in reflex arc Spinal Cord Organization Gray matter : mostly cell bodies Spinal reflex integrating center White matter Bundles of myelinated axons Ascending tracts – sensory Descending tracts – motor the cord can be divided into segments by the nerve roots that come off of it Spinal Cord Organization although the rootlets branch off nearly continuously, they coalesce into about 31 discrete nerves along the cord (8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal nerves). At each segment, rootlets appear to come out of both the dorsal and ventral halves of the spinal cord, Dorsal roots- going into the cord Ventral roots- coming out of the of the cord Spinal Cord Organization Posterior (dorsal) horn contains somatic and visceral sensory nuclei deals with sensory perception, and receives information from the periphery through the dorsal root. Anterior (ventral) horn deals with somatic motor control contain the a-motor neurons , whose axons exit the cord via the ventral roots and travel directly to the muscles. Lateral horn contains visceral motor neurons Gray commissures contain axons that cross from one side to the other
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Along the dorsal root is a collection of cell bodies called the dorsal root ganglion . Inside the ganglion are the cell bodies of all the receptor neurons that send processes out to the periphery. The free nerve ending in the tip of your finger that feels the paper cut actually has its cell body back in the dorsal root ganglion. Differentiating Levels of the Cord Overall shape Cervical sections tend to be wide and squashed looking, like an oval. Compare the cervical section to the round lumbar section. ventral horn enlargement - At segments that control a limb, the motor neurons are large and numerous. This causes enlarged ventral horns in two places: the lower cervical sections (C5- C8) and the lumbar/sacral sections. Differentiating Levels of the Cord Proportion of white matter to gray matter The amount of white matter relative to grey matter decreases as you move down the cord. in the white matter of the cervical cord you have all of the axons going to or from the entire body, more or less. In sacral cord the white matter contains only those axons going to or from the last couple of dermatomes - all other axons have "gotten off" at higher levels. White Matter
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Somatosensory - Spinal Cord Neurons of the Cord Afferent...

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