The document summarizes ascending and descending tracts in the spinal cord that transmit sensory and motor information between the spinal cord and brain. It describes the three neuron chain of ascending tracts that transmit exteroceptive, interoceptive, and proprioceptive sensory information from the peripheral receptors to the brain. It outlines the major ascending tracts - lateral and anterior spinothalamic tracts for pain/temperature and touch/pressure, and the posterior white column and cuneate and gracilis fasciculi for proprioception. It also summarizes the descending motor tracts including the corticospinal, rubrospinal, vestibulospinal, reticulospinal and tectospinal tracts that

1. Ascending& Descending tracts Dr. Israa M. Sulaiman Department of Anatomy IMS/MSU

6. CENTRAL NERVOUS SYSTEM integration / processing / modulating stimulus receptor neurone motor / descending tracts effector organ / response PNS transmission lower motor neurone sensory / ascending tracts

15. ascending sensory pathway are organized in three neuronal chain - First order neurone - Second order neurone - Third order neurone

17. dorsal root dorsal root ganglion spinal nerve dorsal horn FIRST ORDER NEURON

21. ascending sensory pathway ( in general form ) from sensory endings to cerebral cortex ( note the three neurons chain )

22. ascending tracts in spinal cord

25. Main somatosensory pathways sensation receptors pathways destination Pain and temperature Free nerve endings Lateral STT Spinal lemniscus Postcentral gyrus Light touch and pressure Free nerve endings Anterior STT Spinal lemniscus Postcentral gyrus Discriminative touch, vibratory sense, conscious muscle joint sense Meissner’s corpuscle, pacinian corpuscles, muscle spindles, tendon organs Fasciculus gracilis and cuneatus Medial lemniscus Postcentral gyrus

30. pain and temperature pathways

33. touch and pressure pathways

37. lower 6 thoracic segments lumbar segments sacral segments cervical segments upper 6 thoracic segments fasciculus gracilis fasciculus cuneatus [ nucleus G & C ] in medulla G C

39. pathways for conscious proprioception discriminative touch vibratory sense

43. muscle joint sense pathways to cerebellum

45. spinotectal tract spinoreticular tract spino-oloivary tract

48. spinal cord hemisection

55. dorsal 1/3 rd resulting from occlusion of the posterior spinal artery ventral 2/3 rd resulting from occlusion of the anterior spinal artery

56. Descending tracts By the end of this lecture, students should be able to: define the tract enumerate the tracts according to their functional components illustrate and trace the neuronal chain of each tract apply their knowledge of anatomy to correlate with the clinical condition in relation to the injury to these tracts

58. cerebellum premotor cortex motor cortex motor unit muscle spindle pyramidal tract sp cd internreurons & central pattern generator extrapyramidal tracts premotor cortex SMA PMC basal ganglia cortical sensory area MOTOR SYSTEM I II III IV V

65. motor homunculus cerebral cortex

70. cerebral cortex – midbrain - pons - medulla oblongata descending tracts LMN sensory inputs

74. motor decussation medulla oblongata

75. corticospinal tract for fine skilled movements

83. reticulospinal tract

89. dorsal column lateral STT anterior STT pyramidal tracts extrapyramidal tracts nerve roots

90. spinal cord hemisection

91. thank you