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Spinal CordThe Spinal Cord & Spinal NervesSlide 3Spinal Cord ProtectionStructures Covering the Spinal CordExternal Anatomy of Spinal CordInferior End of Spinal CordSpinal Cord & Spinal NervesGray Matter of the Spinal CordWhite Matter of the Spinal CordSpinal NervesA Nerve PlexusCervical PlexusPhrenic NerveBrachial PlexusBranches off Brachial PlexusLumbar PlexusBranches of Lumbar PlexusSacral PlexusBranches of Sacral PlexusSciatic Nerve BranchesDermatomes & MyotomesSlide 29Tracts of the Spinal CordLocation of Tracts inside CordFunction of Spinal TractsSlide 33Spinal ReflexesReflex ArcIllustration of the Stretch ReflexIllustration of Tendon ReflexFlexor (withdrawal) ReflexCrossed Extensor Reflex1Spinal CordI. AnatomyII. Physiology2The Spinal Cord & Spinal NervesTogether with brain forms the CNSFunctions1. spinal cord reflexes2. integration (summation of inhibitory and excitatory) nerve impulses3. highway for upward and downward travel of sensory and motor information3Spinal CordI. Anatomy1. Protective Structures2. External 3. Internal4. Spinal Nervesa. Coveringb. Distributionc. DermatomesII. Physiology4Spinal Cord Protection1. vertebral column5Structures Covering the Spinal Cord2. MembraneA. Dura mater - dense irregular CT tubeSubdural space filled with interstitial fluidB. Arachnoid = spider web of collagen fibersA. Subarachnoid space = CSFC. Pia materthin layer covers BVdenticulate ligs hold in place6External Anatomy of Spinal CordFlattened cylinder16-18 Inches long & 3/4 inch diameterIn adult ends at L2In newborn ends at L4Growth of cord stops at age 51. Cervical enlargementupper limbs2. Lumbar enlargementlower limbs7Inferior End of Spinal Cord1. Conus medullariscone-shaped end of spinal cord2. Filum terminalethread-like extension of pia materstabilizes spinal cord in canal3. Caudae equinae (horse’s tail)dorsal & ventral roots of lowest spinal nerves4. Spinal segmentarea of cord from which each pair of spinal nerves arisesFilum terminaleConus medullaris8Spinal Cord & Spinal NervesSpinal nerves begin as roots1. Dorsal or posterior root is incoming sensory fibersdorsal root ganglion (swelling) = cell bodies of sensory nerves2. Ventral or anterior root is outgoing motor fibersPosterior Root(Sensory)Anterior Root(Motor)10Gray Matter of the Spinal CordCentral canal continuous with 4th ventricle of brainGray matter is shaped like the letter H or a butterflycontains neuron cell bodies, unmyelinated axons & dendritespaired dorsal and ventral gray horns lateral horns only present in thoracic spinal cordgray commissure crosses the midline11White Matter of the Spinal CordWhite matter covers gray matterAnterior median fissure deeper than Posterior median sulcusAnterior, Lateral and Posterior White Columns contain axons that form ascending & descending tracts12Spinal Nerves31 Pairs of spinal nervesNamed & numbered by the cord level of their origin1. 8 pairs of cervical nerves (C1 to C8)2. 12 pairs of thoracic nerves (T1 to T12)3. 5 pairs of lumbar nerves (L1 to L5)4. 5 pairs of sacral nerves (S1 to S5)5. 1 pair of coccygeal nervesMixed sensory & motor nerves16A Nerve PlexusJoining of ventral rami of spinal nerves to form nerve networks or plexusesFound in neck, arm, low back & sacral regionsNo plexus in thoracic regionintercostal nn. innervate intercostal spacesT7 to T12 supply abdominal wall as well17Cervical PlexusVentral rami of spinal nerves (C1 to C5)Supplies parts of head, neck & shouldersPhrenic nerve (C3-C5) keeps diaphragm aliveDamage to cord above C3 causes respiratory arrest18Phrenic Nerve19Brachial PlexusVentral rami from C5 to T1Supplies shoulder & upper limbPasses superior to 1st rib & under clavicleAxillary n. = deltoid & teres m.Musculocutaneous n. = elbow flexorsRadial n. = shoulder & elbow extensorsMedian & ulnar nn. = flexors of wrist & hand20Branches off Brachial Plexus22Ventral rami of L1 to L4 Supplies abdominal wall, external genitals & anterior/medial thighInjury to femoral nerve causes inability to extend leg & loss of sensation in thighInjury to obturator nerve causes paralysis of thigh adductorsLumbar Plexus23Branches of Lumbar PlexusNotice: Femoral and Obturator nervesFound anterior and medial to hip joint24Sacral PlexusVentral rami of L4-L5 & S1-S4Anterior to the sacrumSupplies buttocks, perineum & part of lower limbSciatic nerve = L4 to S3 supplies post thigh & all below kneePeroneal nerve injury produces foot drop or numbnessTibial nerve injury produces calcaneovalgus (loss of function on anterior leg & dorsum of foot)25Branches of Sacral Plexus26Sciatic Nerve BranchesNotice: Common Peroneal nerve and Tibial nerve behind the kneeNotice: Sciatica pain extends from the buttock down the leg to the footmay be sign of herniated disc27Dermatomes & MyotomesEach spinal nerve contains both sensory & motor nerve fibersDermatomearea of skin supplied by one spinal nerveoverlap prevents loss of sensation if one damagedsensory anesthesia requires 3 spinal nerves to be blockedSkin on face supplied by Cranial Nerve V29Spinal CordI. AnatomyII. Physiology1. Tracts2. Reflexesa. Stretchb. Tendonc. Flexord. Crossed Extensor30Tracts of the Spinal CordFunction of tracts1. highway for sensory & motor information2. sensory tracts ascend3. motor tracts descend Naming of tractsindicates position & direction of signalexample = anterior spinothalamic tractimpulses travel from spinal cord towards brain (thalamus)found in anterior part of spinal cord31Location of Tracts inside CordMotor tracts Sensory tractspyramidal tract (corticospinal) spinothalamic tractextrapyramidal tract posterior columnspinocerebellar32Function of Spinal Tractstwo-point discrimination, pressure and vibrationpain, temperature, deep pressure33Function of Spinal Tractsvoluntary movements, posture & muscle tone, equilibrium34Spinal ReflexesAutomatic response to change in environmentIntegration center for spinal reflexes is gray matter of spinal cordExamplessomatic reflexes result in skeletal muscle contractionautonomic (visceral) reflexes involve smooth & cardiac muscle and glands.heart rate, respiration, digestion, urination, etcNote: cranial reflexes involve cranial nerves35Reflex ArcSpecific nerve impulse pathway5 components of reflex arc1. receptor 2. sensory


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ESSEX BIO 121 - Spinal Cord

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