Spinal Cord
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Spinal Cord

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

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

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    Spinal Cord Spinal Cord Presentation Transcript

    •  Structure  Function  Tracts
    • 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
    •  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
    •  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
    •  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
    • 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
    •  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
    •  Tract is a bundle of nerve fibers (within CNS) having the same :-  Origin  Course  Destination  Function
    •  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
    •  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.
    • Ascending Spinal Tracts
    •  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
    • 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
    •  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
    •  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
    •  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
    •  Info:Present only above level L3  Ist Neuron in Clark’s column  2nd Neuron: terminate ipsilaterally in the cerebellar cortex
    •  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
    • DESCENDINIG TRACT PYRAMIDAL TRACT (DIRECT) ANTERIOR CORTICOSPINAL TRACT LATERAL CORTICOSPINAL TRACT EXTRAPYRAMIDAL TRACT (INDIRECT) RETICULOSPINAL TRACT VESTIBULOSPINAL TRACT TECTOSPINAL TRACT RUBROSPINAL TRACT
    • 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
    •  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
    •  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
    •  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)
    •  Function : controls flexor muscle tone  Origin : Red nucleus  Course :cross to (lower cervical segment)  Termination: lateral white column
    •  Lateral vestibulospinal tract  Function: control extensor muscle tone : antigravity maintenance of posture  Origin : lateral vestibular (Derter’s) nucleus  Termination :ventral funniculus
    • • Medial vestibulospinal tract Function: control movement of head :maintain equilibrium Origin:medial vestibular nucleus Termination: ventral funniculus + medial funniculus