3rd Lecture PDF

Posterior White Column-Medial Lemniscal Pathway Modality: Discriminative Touch Sensation (include Vibration) and Conscious Proprioception Receptor: Most receptors except free nerve endings Ist Neuron: Dorsal Root Ganglion 2nd Neuron: Dorsal Column Nuclei (Nucleus Gracilis and Cuneatus) ---Internal A...

Posterior White Column-Medial Lemniscal Pathway Modality: Discriminative Touch Sensation (include Vibration) and Conscious Proprioception Receptor: Most receptors except free nerve endings Ist Neuron: Dorsal Root Ganglion 2nd Neuron: Dorsal Column Nuclei (Nucleus Gracilis and Cuneatus) ---Internal Arcuate Fiber Lemniscal Decussation ---Medial Lemniscus 3rd Neuron: Thalamus (VPL) Internal Capsule ----- Corona Radiata Termination: Primary Somesthetic Area (S I) Posterior White Column-Medial Lemniscal Pathway Discriminative touch, vibratory sense, and conscious muscle-joint sense Posterior Column tract consists of: Fasciculus gracilis Transmits information coming from areas inferior to T6 Fasciculus cuneatus Transmits information coming from areas superior to T6 Posterior Columns Midbrain Nucleus gracilis nucleus cuneatus Medial lemniscus Medulla oblongata Fasciculus cuneatus fasciculus gracilis Fine-touch, vibration, pressure, and proprioception sensations from right side of body 42 Primary Somatosensory (SI) Cortex  Axons from third-order thalamic neurons terminate in the primary somatosensory (SI)cortex  subdivided into four distinct areas; from anterior to posterior, these are Brodmann areas 3a, 3b, 1, and 2  Area 3a: muscle spindle afferents (mainly)  Area 2: Golgi tendon organs, and joint afferents (mainly).  Areas 3b and 1: They receive cutaneous afferents from receptors such as Meissner corpuscles and Merkel cells). also receive input from cutaneous receptors that transmit pain and temperature lateral spinothalamic tract Modality: pain and temperature Receptors: free nerve endings 1st Neuron: Dorsal root ganglia Ventral 2nd Neuron: the posterior gray nuclei in column (substantia gelatinosa) thalamus The axons of 2nd order neurons cross obliquely to the opposite side in the anterior gray and white commissures , ascending in the contralateral white column as the lateral spinothalamic tract 3rd Neuron: Thalamus (VPL) Lateral spinothalamic Internal Capsule ----- Corona tract Radiata Termination: Primary Somesthetic Area (S I) and Widespread Cortical Region Pain and temperature Midbrain sensations from right side of body Rexed laminae Lamina 1 relay information related to pain and temperature Lamina 2: relay information related to pain and temperature (pain modulation) Lamina 3 and 4: nucleus proprius; these laminae have many interneurons Lamina 5: relay information related to pain and temperature Lamina 6: presents only at the cervical and lumbar enlargements and receives proprioception Lamina 7: Intermedio-lateral nucleus, contains preganglionic fibers of sympathetic (T1 -L2). Intermedio-medial nucleus ,all over the spinal cord, receive visceral pain. Dorsal nucleus of Clark’s presents at (C8 – L2 or T1L4) , relay center for unconscious proprioception lateral spinothalamic tract Lamina 1+ 5: the spinothalamic tract ascend which transmit pain, temperature and touch. (A delta fibers) Lamina 1+ 2: the spinothalamic tract ascend (C fibers). Posterolateral tract of Lissauer located between the posterior white column and the lateral white column Other Terminations of the Lateral Spinothalamic Tract Reticular formation: (majority of the slow pain fibers) individual becomes aware of the pain Cingulate gyrus: interpretation of the emotional aspect of pain Insular gyrus: concerned with the interpretation of pain stimuli from the internal organs of the body and brings about an autonomic response thalamus reticular formation Anterior spinothalamic tract Modality: crude touch and pressure Receptors: free nerve endings 1 Neuron: Dorsal root ganglia 2 Neuron: the posterior gray st nd column (nucleus proprius) The axons of 2nd order neurons cross obliquely to the opposite side in the anterior gray and white commissures , ascending in the contralateral white column as the Anterior spinothalamic tract 3rd Neuron: Thalamus (VPL) Internal Capsule ----- Corona Radiata Termination: Primary Somesthetic Area (S I) Spinotectal Tract ascend in the anterolateral white column lying close to the lateral spinothalamic tract Terminate: superior colliculus Provides afferent information for spinovisual reflexes In Medulla: ant spinothalamic tract + spinotectal + lateral spinothalamic = spinal leminiscus Posterior spinocerebellar muscle and joint sensation 1st order neuron axons terminate at the base of post gray column (nucleus dorsalis or Clarks nucleus) the axons of 2nd order neurons enter posterolateral part of the lateral white matter on the same side ascend as the posterior spinocerebellar tract to medulla oblongata Terminates in cerebellar cortex (through inferior cerebellar peduncle)  note: axons of lower lumbar and sacral spinal nerves ascend in the posterior white column until they reach L3 or L4 segments where they synapse with nucleus dorsalis Anterior spinocerebellar tract muscle and joint sensation 1st order neuron axons terminate at the base of post gray column (nucleus dorsalis) the majority of axons of 2nd order neurons cross to opposite side and ascend as anterior spinocerebellar tract in the contralateral white column  the minority of axons ascend as anterior spinocerebellar tract in the lateral white column Of the same side ascend as anterior spinocerebellar tract to medulla oblongata and pons Terminates in cerebellar cortex (through superior cerebellar peduncle)  the fibers that crossed over in spinal cord cross back within cerebellum Spinocerebellar Tracts PONS Cerebellum Medulla oblongata Anterior spinocerebellar tract Spinal cord Proprioceptive input from Golgi tendon organs, muscle spindles, and joint capsules Posterior spinocerebellar tract