Spinal Cord Spinal Cord Brought to you by Spinal Cord Runs through the vertebral canal Extends from foramen magnum to second lumbar vertebra Regions Cervical Thoracic Lumbar Sacral Coccygeal Gives ris.
Spinal Cord Brought to you by Spinal Cord • • • Runs through the vertebral canal Extends from foramen magnum to second lumbar vertebra Regions – – – – – • Cervical Thoracic Lumbar Sacral Coccygeal Gives rise to 31 pairs of spinal nerves – All are mixed nerves • • Not uniform in diameter – Cervical enlargement: supplies upper limbs – Lumbar enlargement: supplies lower limbs Conus medullaris- tapered inferior end – Ends between L1 and L2 • Cauda equina - origin of spinal nerves extending inferiorly from conus medullaris Brought to you by Meninges • Connective tissue membranes – Dura mater: outermost layer; continuous with epineurium of the spinal nerves – Arachnoid mater: thin and wispy – Pia mater: bound tightly to surface • Forms the filum terminale – anchors spinal cord to coccyx • Forms the denticulate ligaments that attach the spinal cord to the dura • Spaces – Epidural: external to the dura • Anesthestics injected here • Fat-fill – Subdural space: serous fluid – Subarachnoid: between pia and arachnoid • Filled with CSF Brought to you by Cross Section of Spinal Cord • Anterior median fissure and posterior median sulcus – deep clefts partially separating left and right halves • • Gray matter: neuron cell bodies, dendrites, axons – Divided into horns • Posterior (dorsal) horn • Anterior (ventral) horn • Lateral horn White matter – Myelinated axons – Divided into three columns (funiculi) • Ventral • Dorsal • lateral – Each of these divided into sensory or motor tracts Brought to you by Cross section of Spinal Cord • • Commissures: connections between left and right halves – Gray with central canal in the center – White Roots – Spinal nerves arise as rootlets then combine to form dorsal and ventral roots – Dorsal and ventral roots merge laterally and form the spinal nerve Brought to you by Organization of Spinal Cord Gray Matter • Recall, it is divided into horns – Dorsal, lateral (only in thoracic region), and ventral • Dorsal half – sensory roots and ganglia • Ventral half – motor roots • Based on the type of neurons/cell bodies located in each horn, it is specialized further into regions – – – – Somatic sensory (SS) - axons of somatic sensory neurons Visceral sensory (VS) - neurons of visceral sensory neur Visceral motor (VM) - cell bodies of visceral motor neurons Somatic motor (SM) - cell bodies of somatic motor neurons Brought to you by Gray Matter: Organization Brought to you by White Matter in the Spinal Cord • Divided into three funiculi (columns) – posterior, lateral, and anterior – Columns contain different types of fibers (Ascend., Descend., Trans.) • Fibers run in three directions – Ascending fibers - compose the sensory tracts – Descending fibers - compose the motor tracts – Commissural (transverse) fibers - connect opposite sides of cord Brought to you by White Matter Fiber Tract Generalizations • Pathways decussate (most) • Most consist of a chain of two or three neurons • Most exhibit somatotopy (precise spatial relationships) • All pathways are paired – one on each side of the spinal cord Brought to you by White Matter: Pathway Generalizations Brought to you by Nonspecific Ascending Pathway • • • • • • Include the lateral and anterior spinothalamic tracts Lateral: transmits impulses concerned with pain and temp to opposite side of brain Anterior: transmits impulses concerned with crude touch and pressure to opposite side of brain 1st order neuron: sensory neuron 2nd order neuron: interneurons of dorsal horn; synapse with 3rd order neuron in thalamus 3rd order neuron: carry impulse from thalamus to postcentral gyrus Brought to you by Specific and Posterior Spinocerebellar Tracts • Dorsal Column Tract AKA Medial lemniscal pathway Fibers run only in dorsal column Transmit impulses from receptors in skin and joints Detect discriminative touch and body position sense =proprioception • 1st order neuron - a sensory neuron • synapses with 2nd order neuron in nucleus gracilis and nucleus cuneatus of medulla • 2nd order neuron.- an interneuron • decussate and ascend to thalamus where it synapses with 3rd order neuron • 3rd-order (thalamic neurons) •transmits impulse to somato- Brought to you by Spinal Cord Trauma and Disorders • Severe damage to ventral root results in flaccid paralysis (limp and unresponsive) • Skeletal muscles cannot move either voluntarily or involuntarily • Without stimulation, muscles atrophy • When only UMN of primary motor cortex is damaged • spastic paralysis occurs - muscles affected by persistent spasms and exaggerated tendon reflexes • Muscles remain healthy longer but their movements are no longer subject to voluntary control • Muscles commonly become permanently shortened • Transection (cross sectioning) at any level results in total motor and sensory loss in body regions inferior to site of damage • If injury in cervical region, all four limbs affected (quadriplegia) • If injury between T1 and L1, only lower limbs affected (paraplegia) Brought to you by Spinal Cord Trauma and Disorders • Spinal shock - transient period of functional loss that follows the injury • Results in immediate depression of all reflex activity caudal to lesion • Bowel and bladder reflexes stop, blood pressure falls, and all muscles (somatic and visceral) below the injury are paralyzed and insensitive • Neural function usually returns within a few hours following injury • If function does not resume within 48 hrs, paralysis is permanent • Amyotrophic Lateral Sclerosis (aka, Lou Gehrig’s disease) • Progressive destruction of anterior horn motor neurons and fibers of the pyramidal tracts • Lose ability to speak, swallow, breathe • Death within yrs • Cause unknown (90%); others have high glutamate levels Brought to you by • Poliomyelitis • Virus destroys anterior horn motor neurons Primary Systems Dorsal column-Medial Lemniscal System Corticospinal Tract Brought to you by Dorsal Column (SC) -Medial Lemniscal (brain stem) System • 1° sensory function – brings info from sensory receptors in the periphery all the way to the 1° somatic sensory cortex • Refer to the postcentral gyrus of parietal lobe! • Via the SC, brainstem, and thalamus • A 3-neuron-circuit (sites of synaptic contact): Brought to you by Dorsal Column (SC) -Medial Lemniscal (brain stem) System i DRG cells – bipolar (pseudounipolar) neurons receive info from peripheral sensory receptors and bring it to SC and bs, where the info is 1st processed (through dorsal column) *synapse at relay nucleus in medulla: dorsal column nucleus ii Axons of these neurons from the dorsal column nucleus cross over (decussate) here at the medulla and continue as the medial lemniscus thalamus iii These next thalamic neurons send their axons into the internal capsule (white mattter underlying the cortex) synapse at 1° somatic sensory cortex Brought to you by Corticospinal Tract • This pathway serves a 1° motor function – bringing information down from the primary motor cortex (where?) all the way down to skeletal muscle in the periphery (activating muscle contraction) • This pathway contains only synapse (unlike the DCML system, which contains (how many)? Brought to you by Corticospinal Tract i 1° motor cortical neuron (pre-central gyrus of the frontal lobe) internal capsule ventral surface of midbrain pyramids on ventral surface of medulla These axons decussate at caudal medulla and travel in the lateral column of the SC synapse at motor neurons in the ventral horn these axons travel to the spinal nerve (through ventral nerve roots) to synapse at the muscles Brought to you by Overview of SC Anatomy –as it relates to these systems • Gray matter: - dorsal (sensory) and ventral (motor) horns - intermediate zone – integration of sensory and motor functions (inter-neurons, reflexes), which serve direct spinal reflexes • White matter: - nerve tracts (myelin) - dorsal column (contains dorsal column) - lateral column (contains motor descending axons) - ventral column (will discuss later) Many of the CNS slices we will view, such as this next slide, are myelinstained – so white mater appears dark Central canal – lowest component of ventricular system Brought to you by Myelin-Stained Spinal Cord Sect Brought to you by Brought to you by This platform has been started by Parveen Kumar Chadha with the vision that nobody should suffer the way he has suffered because of lack and improper healthcare facilities in India We need lots of funds manpower etc to make this vision a reality please contact us Join us as a member for a noble cause Brought to you by Our views have increased the mark of the 20,000 Thank you viewers Looking forward for franchise, collaboration, partners Brought to you by Contact ,011-41425180 ,011-25464531 :-Us 011-66217387 91-+,91-9818308353+ 9818569476 othermotherindia@gm ail.com www.other-mother Saxbee Consultants Details :-www.parveenchadha.com in https://cparveen.wix.com/othe r-mother https://twitter.com/othermo therindi http://www.linkedin.com/profile/view?id=326103341&trk=nav_respons ive_tab_profile https://www.facebook.com/pages/Other-Mother-Nursing-Crusade/224235 031114989?ref=hl A WORLDWIDE MISSITION Brought to you by JOIN US ... spinal cord Brought to you by White Matter: Pathway Generalizations Brought to you by Descending (Motor) Pathways • Descending tracts deliver motor instructions from the brain to the spinal cord. .. diffusely as they enter the spinal cord and medulla • Some branches take part in spinal cord reflexes • Others synapse with second-order neurons in the cord and medullary nuclei Brought to you by Three... appears dark Central canal – lowest component of ventricular system Brought to you by Myelin-Stained Spinal Cord Sect Brought to you by Brought to you by This platform has been started by Parveen Kumar