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13 Cards in this Set
- Front
- Back
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lateral descending pathways |
-in lateral column -project primarily to spinal neurons that control distal muscles of the limbs -signals primarily for limb movements |
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medial descending pathways |
-in ventral column -project primarily in spinal neurons that control axial and proximal limb muscles -motor signals for movements that control posture and locomotion |
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corticospinal tract |
-origin: M1 (half) PMC, SMC, and S1 -course: post. limb of int. capsule --> cerebral peduncle -->pyramids -laterality: 75-95% of pyramids decussate (lateral CST); rest make up ipsilateral ventral CST (most ultimately cross) -destination: ventral horn (primarily distal and flexors) and S1 to base of DH -function: excite (glutamate) alpha-motor neurons and interneurons; provides rapid responsive fractional movements and the fine control of distal limb and hand muscles -dysfunction: contralateral weakness, abnormal reflexes, Babinski's sign, spastic paresis |
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corticobulbar tract |
-origin: head region of M1, PMC, SMC, and S1, and frontal eye fields of frontal cortex -course: genu of IC, mid of cerebral peduncle -laterality: bilateral except lower VII, IX, X, and XII are mainly crossed before synapse and XI is only uncrossed -destination: interneurons and motor neurons of CN nuclei and interneurons of adjacent reticular formation -function: upper motor neuron activation of CN motor nuclei -dysfunction: analogous to CST (spasticity) |
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corticorubro-spinal pathway overview |
-comprised of cortico-rubral +rubral-spinal tract -minor pathway in men -carries motor commands to brain stem and spinal interneurons -assists the CST in coordination -facilitates activity in the flexor motor nuclei and inhibits extensor -aids in muscle tone and reflexes -lesions produce contralateral tremor, ataxia, chorea, which solves with time |
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cortico-rubral tract |
-origin: M1, PMC, SMC, and S1 -course: post limb of IC to midbrain -laterality: uncrossed -destination: red nucleus in midbrain -topographical organization: yes -function: excite red nucleus from cortex (which receives info from cerebellum too, allowing it to integrate coordination and motor commands) |
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rubro-spinal tract |
-origin: red nucleus -course: decussates in ventral midbrain when emerging, descends laterally in the tegmentum ventral to STT, then descends in lateral column ventral to the lateral CST -laterality: crosses in midbrain -destination: pre-motor interneurons in ventral horn (mostly upper SC --> upper limb) -function: excite pre-motor interneurons |
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cortico-reticulo-spinal pathway overview |
-consists of cortico-reticular and two reticulo-spinal tracts -functions in locomotion and the control of posture, spinal reflexes, and tone -allows for bilateral coordinated control of axial and proximal limb muscles by simultaneously activating pontine (excitatory) and medullary (inhibitory) reticulo-spinal tracts |
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cortico-reticular tract |
-origin: widespread but mainly sensory-motor -course: post limb of IC --> cerebral peduncles -laterality: bilateral, but predominant laterality is organized such that the pathway is primarily crossed (dependent on destination) -destination: pontine or medullary reticular formation -function: both excite and inhibit reticulo-spinal activity |
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medial (pontine) reticulo-spinal tract |
-origin: pontine reticular formation -course: ventral reticular formation of medulla, ventral column of spinal cord -laterality: predominantly uncrossed -destination: alpha and gamma motor neurons and interneurons in medial region of ventral horn and intermediate gray -function: facilitates contractions of primarily axial muscle and proximal limb extensors |
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lateral (medullary) reticulo-spinal tracts |
-origin: medullary reticular formation -course: through bulbar commissures, lateral column of spinal cord -laterality: bilateral -destination: INs of the intermediate grey -function: suppresses muscle contraction of primarily axial and proximal limb muscles |
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lateral vestibulospinal tract |
-origin: lateral vestibular nucleus -course: lateral in brainstem tegmentum through ventral column of SC -laterality: uncrossed -destination: alpha and gamma motor neurons in the medial ventral horn and INs in intermediate grey -function: help mediate posture of body and limbs in response to changes in head position |
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medial vestibulospinal tract |
-origin: medial vestibular nucleus -course: some cross in commissure of medulla; descend in medial longitudinal fasciculus in medulla and ventral column of SC -laterality: bilateral -destination: cervical and upper thoracic SC; motor ad interneurons in medial region of VH -function: moves neck in response to head postion |
