Spinal Cord

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the anatomy and physiology of spinal cord.Including ascending and descending tract

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Spinal Cord

  1. 1.  Structure  Function  Tracts
  2. 2. Long :-  Men=45cm(18inch)  Women=43cm(17inch) Width :-  Cervical and lumbar = 1/2inch thick  Thoracic area = 1/4inch thick  Begins from occipital bone until L1&L2  the end of spinal cord = filum terminal
  3. 3.  Meninges  Epidural = External of dura(fat-fil)  Subdural space = Serous fluid  Subarachnoid = Between pia and arachnoid (CSF filled) Dura mater (dural sheath)=outermost Arachnoid’s mater = thin,movable Pia mater=forms filum terminal,denticulate ligament Connective tissue membranes Subdural space Subarachnoid Epidural
  4. 4.  Spinal segment = spinal nerve  Spinal nerve has two roots  Dorsal root ganglion = swelling like structure Anterior root= ventral root Posterior root=dorsal root SPINAL NERVE
  5. 5.  Spinal cord have 31 segment 8 Cervical 12 Thoracic 5 Lumbar 5 Sacral 1 Coccygeal  The spinal segments that contribute to the nerve of the upper are enlargement to the form cervical and lumbar enlargements
  6. 6. vertebrae spinal segments C1 to C4 (upper cervical) same C4 To C7 (lower cervical) +1 T1 to T7 +2 T7 to T9 +3 T10 L1,L2 T11 L3,L4 T12 L5,S1 L1 sacral and coccygeal nerve
  7. 7.  Spinal Arteries :-  Anterior (1) & Posterior (2) Spinal Artery from Vertebral artery  Radicular Arteries :-  Segmental arteries from Vertebral,Ascending Cervical,Intercostal and Lumbar Artery  Venous Drainage veins :-  Longitudinal & Radicular Veins Intervertebral veins Internal Vertebral Venous Plexus external vertebral venous plexus segmental veins
  8. 8.  Tract is a bundle of nerve fibers (within CNS) having the same :-  Origin  Course  Destination  Function
  9. 9.  The name of the tract = origin = destination  The axons within each tract are grouped according to the body region innervated  Long tracts at white matter  Short tracts at gray matter  There are 2 types of tract :-  Ascending tract =Sensory  Descending tract =Motor
  10. 10.  Decussation is the cross-over of the tract from one side to the other.  Therefore,there are instances where the left side of the body is controlled by the right brain hemisphere.  Decussation occurs at different locations for each tracts.
  11. 11. Ascending Spinal Tracts
  12. 12.  Contain a sequence of 3 neurons from the receptor to the cerebral cortex  1st order neuron: Sensory neuron that delivers information from the receptor to the CNS.  2nd order:  Has cell body in the spinal cord or medulla oblongata  Axon decussate  3rd order neuron:  Has cell body in thalamus  Axon terminates on cerebral cortex ipsilaterally 1 2 3
  13. 13. Modality: Discriminative Touch Sensation Conscious Proprioception Receptor: Most receptors except free nerve endings Ist Neuron: Dorsal Root Ganglion (Spinal Ganglion) Dorsal Column Nuclei (Nucleus Gracilis Thalamus (VPLc) ,Corona Radiata Termination: Primary Somesthetic Area (S I) Posterior White Column-Medial Lemniscal Pathway
  14. 14.  Modality:pain and thermal sensations. Ist Neuron : dorsal horn  2nd Neuron: mostly in the nucleus proprius), decussate within one segment by passing through the ventral white commissure  3rd Neuron: ventral posterior nucleus of the thalamus  Thalamic neurons project to the somatosensory cortex
  15. 15.  Modality:non- discriminative touch and pressure  Ist Neuron : dorsal horn  2nd Neuron: nucleus proprius,crossing to opposite side by passing through the ventral white commissure  3rd Neuron: in ventral posterior nucleus of the thalamus  Thalamic neurons project to the somatosensory cortex
  16. 16.  Ist Neuron neuron lie in base of the dorsal horn of the lumbosacral segments  cross to opposite side, ascend as far as the midbrain  2nd Neuron: terminating in the cerebellar cortex Both spinocerebellar tracts convey sensory information to the same side of the cerebellum
  17. 17.  Info:Present only above level L3  Ist Neuron in Clark’s column  2nd Neuron: terminate ipsilaterally in the cerebellar cortex
  18. 18.  2 Sequence of neuron(from cerebral cortex/brain stem – muscle)  Upper Motor Neuron(UMN) o Spinal cord -> brain o Cell body cross over before terminate on lower motor neuron  Lower Motor Neuron(LMN) o Spinal cord -> muscle o Cell body pass through posterior root of spinal nerve
  19. 19. DESCENDINIG TRACT PYRAMIDAL TRACT (DIRECT) ANTERIOR CORTICOSPINAL TRACT LATERAL CORTICOSPINAL TRACT EXTRAPYRAMIDAL TRACT (INDIRECT) RETICULOSPINAL TRACT VESTIBULOSPINAL TRACT TECTOSPINAL TRACT RUBROSPINAL TRACT
  20. 20. Function:voluntary movement : fine skill movement  Anterior corticospinal tract o Origin:motor cortex (4,6) :somatosensory cortex (1,2,3) o Course:pass through midbrain(cerebral peduncle) pyramid of medulla oblongata o Termination: anterior white column
  21. 21.  Lateral corticospinal tract o Origin: motor cortex (4,6) :somatosensory cortex (1,2,3) o Course: pass through midbrain(cerebral peduncle) (cross over) pyramid of medulla oblongata o Termination: lateral white column o Corticobulbar  innervate cranial nerves  motor nuclei of CNS
  22. 22.  Function: coordination of voluntary and reflex movement : control of muscle tone : control of respiration and diameter of blood vessel  Origin: Reticular formation (pontine & medulla)  Course :pass through medial pontine lateral medulla  Termination: ventral funniculus
  23. 23.  Function: coordination of head and neck to the visual & audio stimuli  Origin : superior colliculus  Course : pass through periaquductal (cross) Dorsal tegmental  Termination: Anterior median fissure (cervical area)
  24. 24.  Function : controls flexor muscle tone  Origin : Red nucleus  Course :cross to (lower cervical segment)  Termination: lateral white column
  25. 25.  Lateral vestibulospinal tract  Function: control extensor muscle tone : antigravity maintenance of posture  Origin : lateral vestibular (Derter’s) nucleus  Termination :ventral funniculus
  26. 26. • Medial vestibulospinal tract Function: control movement of head :maintain equilibrium Origin:medial vestibular nucleus Termination: ventral funniculus + medial funniculus

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