PHAR525SPINALCORD

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AshburnP1
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46165
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PHAR525SPINALCORD
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2010-11-02 21:53:37
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SPINAL CORD
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  1. Gray Matter
    • primarily cell bodies
    • - sensory & motor
    • control of body




    Ganglia (PNS)

    Nuclei (CNS
  2. White Matter
    • primarily myelinated axons
    • - transmission of information




    Nerves (PNS)

    Tracts (CNS)

    Columns (CNS)
  3. Organization of the
    Nervous System
    • CNS: Brain and Spinal Cord (SC)
    • PNS: neural tissue outside of the CNS
    • -delivers sensory info to the CNS
    • -delivers motor commands to periphery
  4. What connect CNS to
    PNS
    • 12 pairs of cranial nerves= extend off the brain
    • 31 pairs of spinal nerves = extend off the sc
  5. Spinal Cord: Vertebrae
    • •Cervical Region
    • –7 vertebrae; 8 spinal nerves
    • •Thoracic Region (Most job to do)
    • –12 vertebrae; 12 spinal nerves
    • •Lumbar Region
    • –5 vertebrae; 5 spinal nerves
    • •Sacral Region
    • –5 fused vertebrae; 5 spinal nerves
    • •Coccyx Region
    • –4 fused vertebrae; 1 spinal nerve
  6. The spinal cord is protected
    by:
    • 1.Adipose Tissue & blood
    • vessels: in epidural space
    • 2.Cerebral spinal fluid: contained in
    • subarachnoid space, ventricles of brain and central canal of SC
    • 3.Vertebrae
    • 4.Meninges
  7. Vertebrae:
    • “enclose” SC
    • •Spinal nerves ‘exit’ via intervertebral foramen
  8. Vertebrae (cont.)
    • •Spinal column (bone) outgrows spinal cord (CNS tissue) at ~4 yrs. Old Why?
    • •Children up to 4 y. o. neurons still grow
    • •Adult SC ends ~ L1 (conus medullaris)
    • •Cauda equina begins
    • Dorsal & ventral roots of L2–S5 spinal nerves extend inferiorly in spinal column
    • & look like horse’s tail
  9. Meninges
    • 4.Collagen & elastin coverings of SC (and brain):
    • -protects from canal -provides stability and shock absorption
    • 3. Membranes (layers) of Meninges:
    • A: Dura Mater
    • B: Arachnoid Mater
    • C: Pia Mater
  10. Dura Mater
    • A.“tough mother”; outermost.
    • Attached to periosteum of cranium and
    • spinal column
    • Tethers spinal cord at the top &
    • bottom of spinal canal:
    • Top: dura “blends with” foramen magnum periosteum & becomes
    • continuous with cranial dura
    • Bottom: dura “blends with” coccygeal ligament, which eventually blends with periosteum of coccyx
    • ie) Filum terminale externus: “terminal
    • thread”; extensions of dura (and pia) at the base of SC
    • (L1) that extend into sacrum & eventually form the coccygeal ligament (which
    • blends with coccyx periosteum
  11. Arachnoid Mater
    • “spidery mother”;middle
    • -trabeculae extend to underlying
    • pia
  12. Pia Mater
    • C.“delicate mother”; innermost
    • -communicates with above arachnoid mater
    • -firmly interwoven with underlying neural
    • tissue
    • -vascularize
    • -laterally extend from SC to provide lateral
    • stability
    • -denticulate ligaments
    • -vertically extends to coccyx to provide
    • vertical stability
    • -filum terminale internus
  13. epidural space
    • between vertebrae & underlying dura
    • -contains blood vessels and adipose tissue (good for anesthesia)
  14. subdural ‘space’:
    between dura & underlying arachnoid
  15. subarachnoid space
    • between arachnoid and pia mater
    • -contains blood vessels & CSF
  16. Lumbar Puncture
    • Lumbar puncture/spinal
    • tap: CSF removed from subarachnoid space
    • detect infections, inflammation, cancer
  17. Spinal Meningitis
    • •Inflammation of meninges due to bacterial or viral infection
    • •Bacterial: usually more severe and contagious
    • H. influenzae type B, N. meningitidis, Strep. pneumoniae
    • •Viral: more frequent,
    • usually milder, usually not fatal
    • •Infants, children, those in close
    • contact
    • •Sx:
    • –Fever (105), nuchal rigidity (stiff
    • neck), photophobia, headache, vomiting
    • –Can lead to deafness, convulsions,
    • retardation, death
    • •Tx:
    • –Confirm with LP. Head CT to determine
    • if cranial meninges involved
    • –Antibiotics such as Rifampin, steroids, i.v. fluids
    • –Preventative Vaccines: HiB for children, Meningococcal for college, Pneumococcal for
    • elderly
  18. Spinal Anesthetic:
    • ‘local’ blockage of sensory & motor nerves
    • -injection into subarachnoid space/CSF @ L3-L4
    • \more diffuse anesthesia
    • -analgesic effects are immediate
  19. Epidural Anesthetic
    • local blockage of sensory (+~motor) nerves
    • -indwelling catheter
    • into epidural space (usually lower lumbar but can be higher)
  20. Gray Matter: nuclei/cell bodies, unmyelinated axons
    Spinal Horns: “Tips” of each line
    in “H” shaped gray matter in SC
    • A: Dorsal (posterior) horns: process sensory
    • information
    • B: Ventral (anterior) horns: process motor
    • information
    • C: Lateral (side) horns: process motor
    • information
  21. Dorsal horn:
    • Visceral: sensory input from organs
    • -Somatic: sensory input from
    • skin, skel. muscles, joints
  22. Ventral horn:
    Somatic: motor output to skeletal muscles
  23. Lateral horn:
    • -Visceral: motor output to organs (glands, smooth
    • muscle)
    • -only located in thoracic & lumbar regions of spinal cord
  24. Dorsal
    Horn
    • ‘posterior’ gray matter of SC (spinal cord)
    • -Somatic (skeletal muscle) and visceral (organs) nuclei here receive sensory information from peripheral receptors (in skeletal muscles,
    • organs).
    • -Afferent fibers carry
    • such sensory information from periphery to CNS
    • -Axons from dorsal
    • roots synapse here
  25. Ventral horn
    • ‘anterior’ gray matter of SC
    • -Somatic motor nuclei
    • here send motor information to peripheral receptors (in skeletal muscles)
    • -Efferent fibers
    • carry such motor information from CNS to periphery
    • -Motor
    • nuclei are located here
  26. Dorsal Root
    • Axons from dorsal
    • root ganglia (nuclei in PNS)
    • -transmits sensory information (a.k.a. afferent
    • fibers) from periphery to dorsal horn nuclei in SC
  27. Dorsal Root Ganglia:
    • cell bodies of sensory neurons
    • -receptor is in periphery
    • -axon is the ‘dorsal root’
    • -synapse on nuclei in dorsal horn of SC
  28. Ventral Root:
    • Axons from ventral (& lateral) horn nuclei in SC
    • -axons of somatic & visceral motor neurons
    • -relay motor information to periphery (a.k.a. efferent
    • fibers)
    • -muscle movement, glandular secretions, etc.
  29. Ventral Root Ganglia
    non existent, nuclei of motor fibers are in ventral horn of SC
  30. Gray Matter Study Tid Bits
    • SAME:
    • Sensory-Afferent, Motor-Efferent
    • DAVE:
    • Dorsal-Afferent, Ventral-Efferent
    • Cell body of sensory
    • neurons is located in dorsal root ganglia
    • Cell body of motor
    • neurons is located in ventral horn
    • • Location nuclei
    • within gray matter determine which body part it controls
    • Neurons in ventral
    • horn of lumbar region control legs & ‘below”
    • -Neurons in dorsal
    • horn of cervical region are sensory for neck and arms
  31. Spinal Nerves:
    • joining of ventral & dorsal roots
    • - sensory + motor axons bundled
    • together
    • -classified
    • as mixed nerves since they transmit
    • sensory AND motor info.
    • 31 pairs: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal
  32. Muscle innervations= myotomes
    Spinal Nerve
    Mapping: Dermatomes
    • •Specific bilateral region of the skin monitored by a single pair of spinal nerves
    • –Overlapping
    • –Sensory + motor
    • •Clinical diagnostic tool
    • –Determine damage to spinal nerve
    • –Location of regional anesthetic
  33. Herpes Zoster (Shingles)
    • •Acute, localized infection of Varicella-zoster virus
    • –Same virus that causes chickenpox
    • –Painful, blistering rash on skin
    • –Contagious? Yes chickenpox, not shingles
    • Etiology:
    • Chickenpox virus from
    • childhood lies latent for years in DRG
    • Reactivated??? virus
    • travels from ganglia to skin of corresponding dermatome resulting an eruption
    • of vesicles
    • Tx:: Usually disappears on its own
    • Anti-viral drugs (Acyclovir)
    • NSAIDs for pain
    • Preventative Varicella vaccine
  34. White Matter
    • outer section of SC; myelinated axons
    • 3 columns on each side of SC
    • -a column is a groups of tracts
    • -combination of sensory and motor tracts
    • -anterior
    • -lateral
    • -posterior
  35. Tract
    bundle of similar myelinated axons

    -sensory or motor
  36. Ascending tracts
    carry sensory info. to brain
  37. Descending tracts:
    carry motor commands to SC
  38. Nerve Plexuses
    • Plexus:
    • Network of nerves that innervate specific areas
    • Details: during development, smaller muscles ‘blend’
    • together ® larger, complex
    • muscles. The nerves (sensory and motor)
    • of these muscles ‘blend’ too ® series of compound
    • nerve trunks
    • •Cervical plexus: Neck, diaphragm
    • •Brachial plexus: Chest, arms
    • •Lumbar plexus: Lower torso, legs
    • •Celiac (solar) plexus:Stomach/diaphragm
  39. Neuronal
    Organization: Overview
    • •Sensory Neurons: info. to CNS
    • –~10 million
    • –Skin and viscera
    • –Conscious / unconscious
    • •Interneurons: relays
    • –~20 billion
    • –Coordinate incoming and outgoing
    • signals
    • •Motor Neurons: info. from CNS
    • –~0.5 million
    • –Effectors such as muscle (and glands)
    • •Somatic: skeletal
    • •Autonomic: cardiac & smooth
    • Voluntary
    • and involuntary
  40. Interneurons (a.k.a. Association
    Neurons)
    • •Neuronal Pools
    • –Interneurons organized into pools
    • •Functional groups of interconnected
    • neurons
    • •Excitatory & inhibitory
    • •Local or diffuse CNS locations
    • –Arranged as “neural circuits”
    • •Interneurons interactions
  41. •Types of Neural Circuits
    • 1.Serial Processing (pain)
    • 2.Reverberation (+feedback,
    • breathing, maintaining consciousness)
    • 3.Convergence( breathing,)
    • 4.Divergence
    • 5.Parallel Processing
  42. Serial Processing
    • 1)Stepwise progression to next neuron ie: Pain sensation;
    • pain en route to consciousness
  43. Reverberation
    • Collateral axon branches feed back to starting point
    • -Positive feedback and \ self perpetuating
    • -Continues until
    • inhibitory stimuli or fatigue ie: Breathing &
    • maintaining consciousness
  44. Convergence:
    • Several neurons synapse on one postsynaptic neuron.
    • -Neurons may be from different neuronal pools and have different functions
    • -inhibitory & stimulatory; conscious &
    • subconscious ie: Breathing (diaphragm is subconscious but can be conscious)
  45. Divergence:
    • From one neuron to several or from one neuron pool to several pools.
    • Permits broad distribution ie: Visual stimuli distributed to
    • consciousness and brain regions that control posture and balance
  46. Parallel Processing:
    • Multiple neurons or neuronal pools processing same information simultaneously
    • -Divergence occurs first
    • Complex behavior or reflexes ie: Withdrawal reflex
    • Withdraw limb, shift weight, feel pain,
    • curse
  47. Reflexes
    • Rapid, automatic
    • motor responses to specific stimuli.
    • -involuntary
    • -little variability
    • -can be modified over time & under certain
    • circumstances
    • -may have more than one synapse
    • -simple neural processing that demonstrates relationship between sensory and motor fibers
    • -serves as foundation for more complicated
    • responses
  48. Cranial reflexes:
    • via cranial nerves. Most processing occurs in brain
    • stem & may include transmitting impulse to higher centers in brain.
  49. Spinal reflexes:
    • via spinal nerves. Most processing occurs in the spinal cord but may include transmitting impulse to
    • higher centers in the brain.
  50. Reflex Arc Overview
    • Neuronal circuit that directs a specific motor response.
    • -usually reaction opposes
    • initial stimuli; arc is negative feedback
  51. Monosynaptic Reflex
    Receptors= muscle spindles
    • Only one synapse
    • ie) patellar/stretch reflex
    • -Automatic, fast
    • regulation of muscle length
    • -no input from brain
    • -sensory afferent directly synapses with motor neuron in
    • SC
    • -no interneuron involved
    • -motor neuron does processing
    • -monosynaptic; fast
  52. Polysynaptic Reflex:
    Overview
    • -Sensory neuron
    • synapses on interneuron(s) in SC before motor neuron is stimulated.
    • -sensory ®interneuron(s) ®motor neuron
    • More complicated response:
  53. Polysynaptic
    Reflex: Withdrawal Reflex
    • Quickly move away from stimulus
    • (especially pain)
    • -Pain receptor
    • stimulated
    • - stronger stimuli ® more dramatic reaction
    • - Sensory neuron
    • synapses on interneuron in SC
    • Interneuron:
    • 1) stimulates flexor muscle (biceps) 2) inhibits extensor
    • muscle (triceps) 3) relays message up SC & to brain
    • Reciprocal Inhibition: If biceps AND triceps were both stimulated,
    • no movement would occur (flexors & extensors are opposing). Interneurons coordinate the stimulation of biceps AND relaxation of
    • triceps. (Reciprocal meaning vice versa)

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