1Listen to the audio lecture while viewing these slides1Psychology 372Physiological PsychologySteven E. Meier, Ph.D.Spinal Cord2Psyc 372 – Physiological PsychologyOverview• Has a central core of non-myelinated neurons (gray matter) surrounded by myelinated neurons (white matter)• Gray matter is shaped like an H• Is shorter than the vertebral column• Is separated into regions which contain structures.3Psyc 372 – Physiological PsychologyDor s al FuniculusLateral FuniculusVentral FuniculusDor s al Hor nVentral HornVentral Corticospinal TractLateral Corticospinal TractSpinal Cord4Psyc 372 – Physiological PsychologySome Structures•Dorsal Horn• Contains s ensory nuclei• Forms clusters of nuclei• Receives information from outside the CNS•Ventral Horn• Contains motor nuclei• Receives information from major motor pathways• Sends information t o muscles• Does not contain clusters – are arranged in columns that run the length of the spinal cord5Psyc 372 – Physiological PsychologySome Structures• Are different sizes depending on where you are in the spinal column.•E.g.• Ventral horn is larger where motor neurons innervate the arms and legs.• Need neurons for regulation• Dorsal Horn is larger where sensory nerves from the limbs enter the spinal cord.• Need more neurons because you have more receptors.6Psyc 372 – Physiological PsychologyInternuncial Neurons• Also called interneurons• Are also in gray matter• Modulate information flowing from sensory neurons towards the brain, and higher brain centers to motor neurons • Modulates neural activity within motor systems.• Are also involved in reflexes.27Psyc 372 – Physiological PsychologyWhite Matter• Surrounds the Gray Matter• Divided into three columns•Dorsal• Lateral •Ventral • Each column contains bundles of ascending and descending axons8Psyc 372 – Physiological PsychologyDorsal Column• Lie between the two dorsal horns• Sends only sensory information via axons to the brain• Uses the Gracile Fasciculus (lower limbs) and Cuneate Fasciculus (upper body) pathways.9Psyc 372 – Physiological PsychologyDor s al FuniculusLateral FuniculusVentral FuniculusDor s al Hor nVentral HornVentral Corticospinal TractLateral Corticospinal TractGracile FasciculusCuneate FasciculusDorsal Column10Psyc 372 – Physiological PsychologyLateral Columns• Sends information to the brain • Also sends information from the brainstem and cortex to lower motor neurons.• Lateral Corticospinal tract.• Sends motor information to Final Common Pathway• Most motor information is sent in this pathway.11Psyc 372 – Physiological PsychologyVentral Columns• Includes ascending and descending axons• Ascending sends information about pain and thermal sensation.• Descending pathways help control axial muscles and posture.• Uses Ventral Corticospinal tract and others•Sends remaining motor information12Psyc 372 – Physiological PsychologyVentral Columns313Psyc 372 – Physiological PsychologySpinal Cord• Divided into four major regions•Cervical•Thoracic•Lumbar•Sacral• Are related to body development segments• Nerves enter and leave through the intervertebral foramen.14Psyc 372 – Physiological PsychologyCervical Nerves•Has 8 segments•Involved with • sensory perception• Motor function on the back of the head, neck, arms15Psyc 372 – Physiological PsychologyThoracic• Has 12 segments• Innervates upper body16Psyc 372 – Physiological PsychologyLumbar and Sacral• Lumbar - 5 segments• Sacral - 5 segments• Innervates the lower body, the back, and legs• Spinal Cord usually terminates in the lumbar area.17Psyc 372 – Physiological PsychologyPyramidal Decussation • Located in the Medulla • Is where the majority of fibers cross over to the opposite side of the body• E.g., 80-85% of motor fibers cross over to contralateral (opposite) side •Uses the lateral co rtico spinal tract• 15-20% remain ipsilateral (on same side)•Uses the ventral co rtico spinal tract.18Psyc 372 – Physiological PsychologyOther Things• Few sensory axons enter at sacral level• As you ascend up the spinal column, more sensory neurons enter.• Most descending axons terminate at cervical levels• Thus, the sacral level has less white matter than at cervical