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Lecture

Descending Spinal Tracts + Why We Eat.docx

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Department
Human Biology
Course
HMB200H1
Professor
All Professors
Semester
Winter

Description
Descending Spinal Tracts - The lateral pathways are involved in voluntary movement of the distal musculature and are under direct cortical control. The consist of: o Corticospinal Tracts o Rubrospinal Tracts - The ventromedial pathways are involved in the control of posture and locomotion and are under brain stem control. They consist of: o Reticulospinal tract (medullary and pontine) o Vestibulospinal tract o Tectospinal tract The Lateral Pathways - Corticospinal tract is the most important component, originating in the neocortex (motor and somatosensory cortex) - Its axons pass through the internal capsule briding the telecephalon and thalamus -> base of cerebral peduncle -> pons -> collect at the medullary pyramid. o Also called the pyramidal tract. - At the junction of medulla and spinal cord, the pyramidal tract decussates, and collect in the lateral column of the spinal cord and form the lateral corticospinal tract that terminate in the dorsolateral region of the ventral horns. - Rubrospinal Tract is a smaller component of the lateral pathways originating in the red nucleus of the midbrain. Its axons decussate in the pons and join those in the corticospinal tract in the lateral column of the spinal cord. - A major source of input to the red nucleus is the same region in the frontal cortex that also contributes to the corticospinal tract. - Lesions in the corticospinal tract alone caused a movement deficit as severe as that observed after lesions in the lateral columns, but many functions gradually reappear as the rubrospinal tract takes over. Another lesion here would reverse the recovery showing that the corticospinal pathway was able to partially compensate for the loss of the corticospinal tract input. The ventromedial pathways - Contains four descending tracts that originate in the brain stem that use sensory information about balance, body position, and the visual environment to reflexively maintain balance and body posture. o vestibulospinal tract o tectospinal tract o pontine reticulospinal tract o medullary reticulospinal tract - The vestibulospinal and the tectospinal tracts function to keep the head balanced o
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