NEUR 0010 - Chapter 14 Flashcards
What are the high, middle, and low levels of motor control?
Strategy, tactics, and execution
What are the structures associated with each level of the motor control hierarchy?
High = strategy (association areas of neocortex, basal ganglia), middle = tactics (motor cortex, cerebellum), low = execution (brain stem, spinal cord)
What are the lateral pathways for?
Voluntary control of distal musculature; under direct cortical control
What are the ventromedial pathways for?
Control of posture and locomotion, under brain stem control
What brain areas control the lateral vs ventromedial pathways?
Cortex vs brainstem
What is the most important component of the lateral tract?
Corticospinal tract
Where do the axons of the CS tract originate?
Mostly in the motor cortex, some in the SS areas of the parietal lobe
Where do the axons of the CS tract go?
Start in the motor cortex or SS area of parietal lobe; pass through internal capsule between telencephalon and thalamus; through cerebral peduncles in the midbrain; through the pons; tract at the base of the medulla in the medullary pyramid
What happens to the CS tract after it becomes the medullary pyramids?
Decussates and continues down to the spinal cord’s lateral column
When does the CS tract decussate?
After becoming the medullary pyramids, right before it continues onto the lateral column of the spinal cord
Where do the CS tract axons terminate?
In the dorsolateral region of the ventral horns and intermediate gray matter (same location as motor neurons/interneurons that control distal muscles, esp. flexors)
What is the rubrospinal tract?
a smaller component of the lateral pathways
Where does the rubrospinal tract originate?
The red nucleus in the midbrain’s tegmentum
Where do the axons in the rubrospinal tract go?
Start in the red nucleus of the midbrain; decussate in the pons; join corticospinal tract in the lateral column of the spinal cord
What is the main source of input to the rubrospinal tract?
Frontal cortex that contributes to the corticospinal tract
What happens after lesions in the lateral pathways?
No fractionated movements of arms/hands; slower movement, less accuracy; functions can gradually recover if only damage to CS tract, but no recovery if damage to both CS and RS tracts; contralateral paralysis if damage to the motor cortex or CS tract
What are the four descending tracts of the VM pathways?
Vestibulospinal, tectospinal, pontine reticulospinal, medullary reticulospinal
What does the VM pathway do?
Uses sensory info about balance/body position/visual environment to maintain balance and posture
What do the vestibulospinal and tectospinal tracts do?
Keep head balanced, turn head to stimuli
Where do the vestibulospinal tracts originate and go?
Start in vestibular nuclei of the inner ear (input from vestibular labyrinth of the inner ear); go bilaterally down spinal cord and activate cervical spinal circuits to guide head movement
Where does the tectospinal tract originate and go?
Starts in superior colliculus of midbrain (input from retina, V1, SS, audition, etc.); maps the world around us and causes the head to focus on a new stimulus
What do the pontine and medullary reticulospinal tracts arise from?
The reticular formation of the brain stem: just under the cerebral aqueduct and fourth ventricle
What does the pontine reticulospinal tract do?
Enhances antigravity reflexes of the spinal cord; facilitates lower limb extensors; maintain standing posture
What does the medullary reticulospinal tract do?
Liberates antigravity reflexes of the spinal cord from reflex control; allows a fine balance of posture vs not
