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SCCC BIO 130 - Lecture Notes

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Nervous System:Spinal Cord and Spinal Nerves(Chapter 13)Lecture MaterialsforAmy Warenda Czura, Ph.D.Suffolk County Community CollegeEastern CampusPrimary Sources for figures and content:Marieb, E. N. Human Anatomy & Physiology 6th ed. San Francisco: Pearson BenjaminCummings, 2004.Martini, F. H. Fundamentals of Anatomy & Physiology 6th ed. San Francisco: PearsonBenjamin Cummings, 2004.Amy Warenda Czura, Ph.D.1SCCC BIO130 Chapter 13 Lecture SlidesNervous System Organization: CNS = brain and spinal cord PNS = all other neural tissueStructures in the PNS: -Ganglia = collection of somas together inone place -Nerves = bundles of axonsStructures in the CNS: -Center = collection of somas with acommon function -Nucleus = a center with a visible boundary -Neural cortex = gray matter (somas)covering the brain -Tracts = bundles of axons with commonorigins, destinations and functions -Columns/funiculi = large tracts in thespinal cord -Pathways = centers and tracts that link thebrain with the bodySensory pathways: receptor  CNSMotor pathways: CNS  effectorAmy Warenda Czura, Ph.D.2SCCC BIO130 Chapter 13 Lecture SlidesSpinal Cord-45cm (18”) from brain to L2-inside vertebral canal (stacked vertebralforamen)-surrounded by CT: Spinal Meninges-support and protect spinal cordAmy Warenda Czura, Ph.D.3SCCC BIO130 Chapter 13 Lecture Slides-three layers (on handout)Amy Warenda Czura, Ph.D.4SCCC BIO130 Chapter 13 Lecture SlidesSpinal cord cross sectional anatomy(on handout)Amy Warenda Czura, Ph.D.5SCCC BIO130 Chapter 13 Lecture Slides-spinal roots exit vertebral canal throughintervertebral foramen-dorsal and ventral roots combine to formspinal nerveAmy Warenda Czura, Ph.D.6SCCC BIO130 Chapter 13 Lecture SlidesSpinal Nerves-31 pair-exit via intervertebral or sacral foramen-name for location of exit on spine, beginningbetween skull and C1Nerves: C1-C8, T1-T12, L1-L5, S1-S5, Co1Amy Warenda Czura, Ph.D.7SCCC BIO130 Chapter 13 Lecture Slides-cord and column grow together until age 4; after column continues but cord does not: roots “stretch” to reach foramen-adult: cord ends at L1-L2-“stretched” spinal roots after L2 = cauda equinaLumbar puncture = “spinal tap”, at L3-L4, draw CSF from subarachnoid spaceAmy Warenda Czura, Ph.D.8SCCC BIO130 Chapter 13 Lecture Slides-intervertebral foramen maintained byintervertebral discs between vertebraeHerniated disc = nucleus pulposus rupturesthrough anulus fibrosis, compressesnerves in intervertebral foramen and/orspinal cord in vertebral canalSlipped disc = intervertebral disc distorted ordisplaced, causes pressureAmy Warenda Czura, Ph.D.9SCCC BIO130 Chapter 13 Lecture SlidesNerve structure(on handout)-axons repair if cut if follow original path-severed nerves do not usually repair: axonsdo not line up correctlyAmy Warenda Czura, Ph.D.10SCCC BIO130 Chapter 13 Lecture Slides-spinal nerves branch off cord near to whatthey innervate-cervical and lumbar enlargements of cordhouse cell bodies of motor neuronsfor muscles of appendages-Dermatome = region of skin surfaceinnervated by one pair spinal nervesAmy Warenda Czura, Ph.D.11SCCC BIO130 Chapter 13 Lecture Slides-most spinal nerves do not go directly totarget: axons from multiple nervesintermingle in a nerve plexus(on handout)Amy Warenda Czura, Ph.D.12SCCC BIO130 Chapter 13 Lecture SlidesTrauma and disorders:-often result from damage or pressureParalysis = loss of motor function: disorder ofventral root or anterior gray hornParesthesias = sensory loss: disorder of dorsalroot or posterior gray horn-complete transection results in loss of bothmotor and sensory below injuryParaplegia = sever between T1 and L4, loss oflower limb functionQuadriplegia = sever in cervical, loss of alllimb function (above C5 can kill)Organization of Neural Pathways10 million sensory neurons (receptor to CNS)500 thousand motor neurons (CNS to effector)20 billion interneurons (coordinate sensoryand motor)Interneurons organized into neuronal pools = functional groups with limited input sources (sensory) and output locations (motor)Amy Warenda Czura, Ph.D.13SCCC BIO130 Chapter 13 Lecture Slides-spread of info organized into neural circuits-5 neural circuits: (on handout)Amy Warenda Czura, Ph.D.14SCCC BIO130 Chapter 13 Lecture SlidesReflexes = rapid automatic response to specific stimuli-used to maintain homeostasis-simple reflex = sensory perception in, motorresponse out-simple reflexes can be grouped together forcomplex actionsReflex arc = single reflex (on handout)-reflex arcs = negative feedback: action opposes stimulus as form of defense, fast response, but not always coordinatedAmy Warenda Czura, Ph.D.15SCCC BIO130 Chapter 13 Lecture SlidesReflex Classification-four ways to classify (on handout)Superficial somatic reflex = stimuli originate at skin or mucous membraneStretch reflex = stimuli from overstretched tendonresponse delayed by each synapse but capable of more complex outputAmy Warenda Czura, Ph.D.16SCCC BIO130 Chapter 13 Lecture SlidesExamples of common spinal reflexes1. Patellar Reflex-monosynaptic stretch reflex-carried on type A fibers-sudden stretch of patellar ligament activatesmuscle spindles → signal quadricepsgroup to contractAmy Warenda Czura, Ph.D.17SCCC BIO130 Chapter 13 Lecture SlidesMuscle spindle = specialized muscle fiber-constantly signal CNS-relaxed = signal less-stretched = signal more → threshold, triggerreflex arc-prevent overstretching of muscles andtendons-aid in maintaining upright positionAmy Warenda Czura, Ph.D.18SCCC BIO130 Chapter 13 Lecture Slides2. Withdrawl reflexes-complex polysynaptic spinal reflex-consists of three parts: a. Flexor reflex = flex to withdraw b. Reciprocal inhibition = inhibit extensors c. Crossed extensor reflex = maintain balancePain → flexor muscles pull limb away → extensors same limb inhibited toprevent opposition to flexion → limbs on opposite side extend to provide balance for sudden flexionAmy Warenda Czura, Ph.D.19SCCC BIO130 Chapter 13 Lecture SlidesReflexes automatic but can be impacted byhigher brain centers:-fine tune or combine reflexes-take cues from reflex for coordinatedvoluntary movements-facilitate or inhibit reflexesReflexes serve as diagnostic tool to assess health and function of spinal cord and brain*Individual spinal nerves and theirinnervations and plexus origins will beexamined in detail in lab along with


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SCCC BIO 130 - Lecture Notes

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