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30 Cards in this Set
- Front
- Back
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Medial tracts
a. Phylogenetic age b. Crossed vs. Uncrossed c. Control d. Examples |
a. Older
b. Uncrossed or bilateral c. extensors, axial/proximal control muscle control of posture and balance d. Vestibulospinal, descending MLF, reticulospinal |
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Lateral pathways
Medial corticospinal tracts a. Phylogenetic age b. Crossed vs. Uncrossed c. Control d. Examples |
a. Newer
b. Crossed c. Flexors, distal muscles for fine motor control d. rubrospinal and lateral corticospinal |
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What is special about the tectospinal and medial corticospinal tracts?
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Lateral physiologically, but placed medially
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Where do axons from the brainstem descend in the spinal cord?
Axons from the motor cortex? |
Medially
Laterally |
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What is the pathway of the vestibulospinal tract?
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Lateral vestibular nucleus (pons) --> descends ipsilaterally to ventromedial spinal cord --> extensor alpha motoneuron pools
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What is the general purpose of the vestibulospinal tract?
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To connect the spinal motor system with the vestibular/cerebellar input --> provide information regarding balance
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What is the pathway of the MLF descending?
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Medial vestibular nucleus --> descends through the thoracic cord bilaterally (but mainly ipsilateral)
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What is the pathway of the lateral reticulospinal tract?
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Medullary reticular formation --> ipsilateral lateral reticulospinal tract --> inhibitory to extensor gamma motoneurons
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What is the pathway of the medial reticulospinal tract?
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Pontine reticular formation --> ipsilateral medial reticulospinal tract --> excitatory to extensor gamma motoneurons
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From where does the medullary reticular formation receive its excitatory input?
Pontine Reticular formation? |
Medullary from cerebral cortex
Pontine from ascending spinoreticular sources in addition to cortical input |
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What is the pathway of the rubrospinal tract?
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Contralateral red nucleus --> cervical spinal cord --> excitatory input to flexor motoneuron pools of the upper extremity
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What is the pathway of the tectospinal tract?
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Deep layers of contralateral superior colliculus --> medial cervical spinal cord --> proximal motoneuron pools
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What is the function of the tectospinal tract?
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As visual input is received by the superior colliculus, tectospinal tract allows for head and trunk positioning
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From where does the corticospinal tract send projections?
To where does it send them? |
From: cerebral cortex involved in motor planning and execution, primary sensory cortex
To: spinal motoneurons innervating flexor and distal muscles involved in fine motor skills |
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What are the direct and indirect routes that fibers from motor planning/execution sites in the cortex reach the spinal cord?
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Coriticospinal tract (direct)
Reticular formation Red nucleus |
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What is the purpose of corticospinal fibers originating in the primary sensory cortex?
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Modulate sensorimotor function within the spinal cord
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How do corticospinal fibers descend?
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Majority cross midline at pyramidal decussation --> lateral corticospinal tract
Few stay ipsilateral --> ventral corticospinal tract --> terminate bilaterally |
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What are the motor areas of the cerebral cortex? Brodman's?
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Primary motor cortex (4)
Premotor cortex (6) Supplementary motor cortex (8) |
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What gets activated...
a. Simple movement of finger? b. Patterned movement of finger? c. Complex movement of a finger? d. Mental rehearsal alone? |
a. Primary motor
b. Primary motor, premotor c. All 3 d. premotor, supplementary |
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How do motor commands proceed?
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Supplementary, premotor, primary motor
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What did researchers find that cortical motoneurons encode?
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Encode movements and their directions, not activation of individual muscles
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What is decerebrate posturing?
What is this due to? |
Cut off cerebrum/midbrain --> elbow extension, arm pronation, wrist/plantar flexion
Vestibular and reticulospinal tracts acting without cortico or rubrospinal balance |
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In decerebrate posturing, why does the excitatory pontine reticular formation dominate over the inhibitory medullary?
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Ascending spinoreticular inputs
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What happens in decerebrate posturing when dorsal afferents (Ia and II) cut?
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Loss of extensor tone because loss of gamma motoneuron activity
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What happens in decerebrate posturing when dorsal root section cut, but anterior lobe also removed?
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Extensor tone returns
Loss of anterior lobe takes away the inhibitory influence from the vestibulocerebellum |
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What happens in decorticate posturing (red nucleus saved)?
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Mixture of flexor and extensor tone (b/c rubrospinal tract does flexion for upper body)
Flexor tone in upper body, extensor tone in lower |
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Upper motor neuron lesion
a. Muscle stretch reflex b. muscle tone c. muscle tissue d. muscle strength e. fine motor control f. pathological reflexes |
a. increase
b. increase c. same d. same e. very diminished f. present |
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Lower motor neuron lesion
a. Muscle stretch reflex b. muscle tone c. muscle tissue d. muscle strength e. fine motor control f. pathological reflexes |
a. decrease
b. decrease c. atrophy d. decrease e. minimally decreased f. absent |
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What is the babinski reflex?
What does it indicate? |
Extensor plantar response to touching bottom of foot
Shows upper motor neuron lesion (decrease in descending inhibitory modulation of sensory afferents from bottom of foot) |
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What is spasticity?
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Positive reflex phenomena in upper motoneuron lesions
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