Lecture 11 9/6/23 Flashcards
What is spinal cord gait generation?
-L3-S4 segment produces an alternate walking pattern
-this pattern is normally suppressed by the brain
-following a spinal cord injury that prevents brain from controlling hind limbs, L3-S4 will take over to resume “walking”
What are the upper motor neuron systems?
-corticospinal
-rubrospinal
-vestibulospinal
-reticulospinal
What are the characteristics of the reticulospinal system?
-diffuse groups of neuronal cell bodies in brainstem
-synapse on LMN in spinal cord
-maintain posture and muscle tone
What are the two portions of the reticulospinal system?
-pons (middle portion of brainstem)
-medulla (back portion of brainstem)
What does the pons faciliate?
flexion
What does the medulla faciliate?
extension
How do the pons and medulla work together?
the two regions counter-balance each other to ensure there is appropriate flexion and extension to maintain posture
What happens when a lesion separates the pons and medulla?
-loss of flexion; only have extension
-get a decerebrate posture which is very stiff- limbs, head, and neck all extended
What are the characteristics of the vestibulospinal system?
-vestibular nuclei in brainstem
-comes from inner ear
-LMN in spinal cord responsible for antigravity muscles
What is the role of the vestibulospinal system?
-senses gravity and movement
-adjusts muscle tone to maintain posture
What is vestibular ataxia?
swaying/staggering gait due to malfunctioning vestibulospinal system
What are the characteristics of the rubrospinal system?
-red nucleus in midbrain
-input on more distal limb muscles for fine movement control
-important in nonprimates
What are the characteristics of the corticospinal tract?
-motor cortex in cerebrum
-spinal LMNs involved in voluntary movement/fine movement
-most important in primates
How does the number of neurons relate to the amount of control in the corticospinal tract?
the more neurons there are in the corresponding section of the brain, the more control you exert over that region of the body (i.e. lots of neurons in part of brain that controls hand = lots of control over hand movement)
