Unit27spinalcord.ppt
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1、The central nervous system The spinal cordThe location and external features:1.Location:In vertebral canal,it extends from foramen magnum to lower border of first lumbar vertebra(adult).2.External features:1.)cervical and lumbosacral enlargements:associate with brachial plexus and lumbosacral plexus
2、.2.)conus medullaris 3.)filum terminale 4.)anterior median fissure,posterior median sulcus,posteriolateral and anterolateral sulci.5.)cauda equina 6.)most segments of spinal cord are located above similarly numbered vertebral body The internal structure of spinal cordGrey matter:posterior,anterior h
3、orn.grey commissure,lateral horn(T1L3)the central canalWhite matter:posterior,lateral,anterior funiculi,anterior white commissure The main nuclei of spinal cord1.Three main kinds of neuron in anterior horn:1.)-motor neuron:axon reaches to skeletal muscle.2.)-motor neuron:axon reaches to skeletal mus
4、cle to play role in reflex regulation of muscle tonus.3.)local circuit neurons 2.The anterior horn cells are organized into medial and lateral groups.The nuclei in the intermediate zone1.The intermediolateral nucleus:Its axons form the sympathetic preganglionic fibers.2.The sacral parasympathetic nu
5、cleus(S24):Its axons form the pelvic visceral nerve.3.The intermediomedial nucleus:It receives branches of posterior root fibers and gives rise to fibers that constitute spinocerebellar tract.The nuclei in the posterior horn1.The nucleus posteromarginalis:Its axons form intersegmental pathways.2.The
6、 substantia gelatinosa:They may be excited by the nociceptive stimuli.3.The nucleus proprius:Its axons cross then contribute to the spinothalamic tracts.4.The nucleus thoracicus:Its axons contribute fibers to the posterior spinocerebellar tract of ipsilateral side.The laminas Based on neuronal size,
7、shape,cytological feature,ten laminas have been distinguished:Lamina I:To respond to noxious stimuli and send axons to the contralateral psinothalamic tractLamina II:To respond to noxious stimuli.Lamina III and IV:Their main input is from fibers that convey position and light touch sense.Lamina V:To
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