Dorsal column tracts_241006_075552.PDF

PRESENTED BY: DR. WALAA ADEL ABD EL MOEZ AHMED A LECTURER OF ANATOMY AND EMBRYOLOGY FACULTY OF MEDICINE- AIN SHAMS UNIVERSITY ‫يال بينا نفتكر سوا!‬ sensory ‫ايلي طاااالع‬ Note that the blue shaded areas are ascending (sensory pathways)....

PRESENTED BY: DR. WALAA ADEL ABD EL MOEZ AHMED A LECTURER OF ANATOMY AND EMBRYOLOGY FACULTY OF MEDICINE- AIN SHAMS UNIVERSITY ‫يال بينا نفتكر سوا!‬ sensory ‫ايلي طاااالع‬ Note that the blue shaded areas are ascending (sensory pathways). ‫اكيد زاكرت وعرفت ان‬ The white matter of the spinal cord is subdivided into three major funiculi (Anterior, ‫ايلي نااااازل‬Motor posterior and lateral) Red shaded areas are Mainly contains ascending and descending (motor descending pathways pathways) First of all! Let us identify A nerve tract is a bundle together what of nerve fibers (axons) is the connecting nuclei of meaning of the central nervous system. tract! Short ascending sensory pathways long ascending sensory pathways 3 2 1 1 2 1-The first-order neuron is a type of pseudounipolar neuron and always has its cell body in the dorsal root ganglion of the spinal nerve with a peripheral axon innervating touch mechanoreceptors and a central axon synapsing on the second-order neuron. 2-The second-order neuron has its cell body either in the spinal cord or in the brainstem. This neuron's ascending axons will cross (decussate) to the opposite side either in the spinal cord or in the brainstem. 3-In the case of touch and certain types of pain, the third- order neuron has its cell body in the ventral posterior nucleus of the thalamus and ends in the postcentral gyrus of the parietal lobe in the primary somatosensory cortex The Ascending sensory pathways could be classified into TWO types Let us start and focus on the long Ascending sensory pathways! e.g: Gracile and cuneate tracts  Let us answer together the following questions? 1-What are they?.............Gracile and cuneate tracts……………….‫هما مين؟‬ 2-What are the major sensations carried by them?............. 1- fine touch 2-vibration ‫الزم تعرف يعني ايه؟‬ 3-Deep pressure 4- Steriognosis 5- conscious proprioception 3- Identify their location on the spinal cord segment?  Fibers of from the lower part of the body below (T6) ascend medially in the dorsal column forming the gracile tract  Fibers of from the upper part of the body below (T6) ascend laterally in the dorsal column forming the gracile tract ‫يال نشوف ال ‪pathway‬‬ ‫كااااااااااامل!‬ Perception of sensations to cerebral cortex occurs through The long ascending ‫يبقي عشان اوصل االحساس من بدايه من‬ somatosensory pathway will ‫المستقبالت واوصله لل‬ typically have three neurons: Sensory cortex we need three order neurons 1- first-order, 2-second-order 3-third-order  Pathways of conscious proprioception and fine touch  First order Neuron: dorsal root ganglion cells which are psudounipolar.  Periphral processes carry sensation from deep receptors (muscles, tendons, joints)  Central processes pass to the spinal cord via the dorsal root. CG  Second order neuron: gracile and cuneate nuclei of the medulla oblongata. Axons of these nuclei cross the median plane forming (internal arcuate fibers)(sensory decussation). Fibers ascend in the brain stem as a medial lemniscus to reach the thalamus.  Third order neuron: ventral posterolateral nucleus of the thalamus (VPLN)…..Axons of theses cells pass through the posterior limb of internal capsule……corona radiate…..sensory cortex.  lamination? ‫طيب‬ Please note the lamination of fibers in dorsal column tracts Lamination: sacral fibers are most medial, cervical fibers are most lateral.  ‫ اتغير‬fibers ‫متنساش ان ترتيب ال‬ after decussation and formation of medial leminiscus! In the medial leminiscus the sacral fibers are most anterior and cervical fibers are most posterior! ‫طيب اركز علي ايه وانا بزاكر؟‬ ‫يال مع بعض نشوف‬ ‫الخالصه‪:‬‬  ‫ كلمات لو سمحت متنسهمش‬4 1- Beginning ‫بينهم‬ 2-Termination 3O 3- position 4-Lamination  Please take a deep breath to continue the second part of our lecture today! ‫‪Short Ascending sensory Tracts‬‬ ‫فكروني يال ليه سميناها‬ ‫?‪Short‬‬ ‫طيب بتتكون من كام‬ ‫?‪order neuron‬‬ ‫طيب هتوصل االحساس‬ ‫ايلي شاياله لمين؟‬  Short Ascending Tracts Four Tracts carry unconscious Proprioception to the cerebellum for coordination of movements. 1- Posterior spinocerebellar tract 2-Anterior spinocerebellar. 3-Spino-olivary. 4-cuneo-cerebellar tract. 1‫مصممه نحفظ االسماء سو‬  1-Name? dorsal spino- cerebellar tract 2-Position? 3-Type of carried sensation? Unconcious proprioception from lower limb and trunk ‫ثم‬ 4-Complete pathway  1- Posterior spino-cerebellar tract 1- carries proprioception from the lower limb& trunk. 2-The central process of DGR cells enter the spinal cord via the dorsal root to end on the ipsilateral clarkʹs nucleus. 3- The tract ascends ipsilaterally in the lateral white column, posterior to anterior spinocerebellar tracts. 4-Enters the ipsilateral cerebellum via the inferior cerebellar peduncle (ICP).  1-Name? VENTRAL spino-cerebellar tract 2-Position? 3-Type of carried sensation? Unconcious proprioception from lower limb ‫ثم‬ 4-Complete pathway  2- Anterior spino-cerebellar tract 1- carries proprioception from the lower limb. 2- the central processes enter the spinal cord via the dorsal root to end on (laminae V,VI,VII)….. clarkes nucleus. 3-Axons forming the tract mostly decussate and few remain ipsilateral. 4- they enter the cerebellum via the superior cerebellar peduncle(SCP) then cross again to reach the ipsilateral cerebellum.  2- cuneo-cerebellar tract 1-Carries proprioception from upper limb to the accessory cuneate nucleus of medulla oblongata. 2-Axons of the accessory cuneate nucleus form the external arcuate fibers (Cuneo- cerebellar tract) which reach cerebellum the ipsilateral cerebellum via the ICP. It is an upper limb equivalent to ………………………………. ????  1-Name? spino- olivary tract 2-Position? 3-Type of carried sensation? Unconcious proprioception from body to cerebellum while learning a new movement ‫ثم‬ 4-Complete pathway  2- Spino-olivary tract 1-Carries proprioception from both upper and lower limbs 2-Fibers cross and ascend at the junction of the lateral and ventral white columns to end on the contralateral olivary nuclei. 3-Olivocerebellar fibers cross and pass via the ICP to reach the ipsilateral cerebellum. IT IS CONCERNED MAINLY IN ………………….. ‫شغل دماغك‪..........‬‬  Other ascending sensory pathways Spino-reticular Spino-tectal tract? tract? Ascending visceral sensory tracts? Spino tectal tract:  first order neuron in the dorsal root ganglion Second order neuron in lamina I and V in all levels of spinal cord. Ascends to end in the superior colliculus of the brain stem. Function: responsible for co-ordination of the eye movement towards the source of stimulation. Spino reticular tract:  first order neuron in the dorsal root ganglion Second order neuron in lamina VII in all levels of spinal cord. Ascends to end in the reticular formation of the brain stem. Function: Transmits sensory impulses to reticular formation to maintain a state of consciousness and awareness