Exam 1 Week 3: Descending Tracts Flashcards
What is the lateral reticulospinal tracts paired with?
Its activity is paired with the corticospinal pathways and the medullary neurons that give rise to this tract are activated by collaterals of corticospinal tracts
Tectospinal tract: function
•Functions in visual-cervical reflexes
Corticospinal Tracts: Lateral Corticospinal tract path
Origin in Cerebral Cortex
- Motor areas
- Sensory areas
- Anterior Cingulate gyrus
- Frontal, parietal, & limbic lobes)
Pass uninterupted htrouhg deep cerebrum & brainstem to spinal cord
Lateral Corticospinal Tract
- 85-90% of fibers
- Decussate in caudal Medulla (pyramidal decussation)
- Descend in contralateral lateral funiculus
- Ens in spinal motor neurons in ventral horn
Corticospinal tract: Function & damage
Function: Fine, controlled, voluntary movement
Damage: typically linkd with spasticity
Lack of myelination (slow develompent or damage) leads to Babinski’s sign
Medial reticulospinal tract: function
- –Monosynaptic & polysynaptic excitation of postural motor neurons
- –Functions to enhance postural set
The Medial Reticulospinal Tract has both Monosynaptic & polysynaptic excitation of postural motor neurons and Functions to enhance postural set
Name the estibulospinal Tracts:
•Two tracts
–Lateral vestibulospinal
–Medial vestibulospinal
Rubrospinal Tract: function
- •Function in fine, controlled, voluntary movement in other primates
- but functions in humans is questionable because of small number of neurons/axons
•Lateral Reticulospinal Tract:: function
- –has Polysynaptic connections that Inhibit motoneurons going to postural muscles
- –Break postural sets in the preparation for motion
It has Polysynaptic connections Inhibit motoneurons going to postural muscles.. It functions to Break postural sets in the preparation for motion. Its activity is paired with the corticospinal pathways and the medullary neurons that give rise to this tract are activated by collaterals of corticospinal tracts
Another name for Lateral Reticulospinal tract
Medullary reticulospinal tract
Rubrospinal tract: Arises from
•Arises from Magnocellular region of Red Nucleus of midbrain
Funiclui of spinal cord (4)
- Dorsal Funiculus
- Dorsolateral Funiculus
- Ventrolateral Funiculus
- Ventral Funiculus
Corticospinal tracts: lack of myelination can cause
Lack of myelination (slow develompent or damage) leads to Babinski’s sign
Medial Reticulospinal tract: path
–Arises from neurons in pontine reticular formation
–Descends bilaterally but mostly ipsilaterally length of the spinal cord in anteromedial funiculus
Rubrospinal tract: Pathway
- •Arises from Magnocellular region of Red Nucleus of midbrain
- •Immediately deccusates to
- Descends in contralateral dorsolateral funiculus with the lateral corticospinal tract
- •Ends on motor neurons and interneurons of ventral horn
tracts that decussate early
- Lateral Corticospinal tract (pyramidal decussation)
- Rubrospinal tract (decussates immediately after arising from red nucleus of midbrain)
- Tectospinal tract (decussates immediately after arising from superior colliculus)
So while the ________ of the medulla actually _________ postural sets, the __________ of the pons ____________ postural sets
So while the lateral reticulospinal tract of the medulla actually breaks postural sets, the medial reticulospinal tract of the pons enhances postural sets
other name for Corticospinal tracts
Pyramidal tracts
what forsms the “final common pathway” to muscle?
Lower motor neurons
Rubrospinal Tract: Everything
- •Arises from Magnocellular region of Red Nucleus of midbrain
- •Immediate deccusates to descend contralaterally
- •Descends thru spinal cord with lateral corticospinal tract in dorsolateral funiculus
- •Ends on motor neurons and interneurons of ventral horn
- •Function in fine, controlled, voluntary movement in other primates
- but functions in humans is questionable because of small number of neurons/axons
Rubrospinal tract arises from Magnocellular region of Red Nucleus of midbrain. Immediate deccusates to descend contralaterally. Descends thru spinal cord with lateral corticospinal tract in dorsolateral funiculus
The rubrospinal tract ends on motor neurons and interneurons of ventral horn. Function in humans is unclear but in other primates functions in fine, controlled, voluntary movement – but questionable in humans because of small number of neurons/axons in this pathway.
Vestibulospinal tracts: Lateral vestibulospinal tract path
- –Arises from neurons in lateral vestibular nucleus
- –Descends ipsilaterally
- –Ends primarily on ventral horn interneurons & some motor neurons
Another name for Medial Reticulospinal tract
Pontine reticulospinal tract
Tracts that decussate distally
Ventral Corticospinal tract (decussates at level that it ends)
Tracts that descend ipsilaterally
- Lateral vestibulospinal
Corticospinal tracts: Everything
Two of them
- Lateral Corticospinal Tract
- Ventral Corticospinal tract
Origin in Cerebral Cortex
- Motor areas
- Sensory areas
- Anterior Cingulate gyrus
- Frontal, parietal, & limbic lobes)
Pass uninterupted htrouhg deep cerebrum & brainstem to spinal cord
Lateral Corticospinal Tract
- 85-90% of fibers
- Decussate in caudal Medulla (pyramidal decussation)
- Descend in contralateral lateral funiculus
- Ens in spinal motor neurons in ventral horn
Ventral Corticospinal Tract
- 10-15% of fibers
- Immediately descend in ipsilateral anterior funiculus
- Decussate at the level the tract ends
- Ends on spinal motor neurons in ventral horn
Function: Fine, controlled, voluntary movement
Damage: typically linkd with spasticity
Lack of myelination (slow develompent or damage) leads to Babinski’s sign
Vestibulospoinal tract: Medial vestibulospinal tract function
–Functions in vestibular-neck reflexes to maintain horizontal gaze
Vestibulospinal tracts: Lateral Vestibulospinal tracts
Function
–Functions in control of posture and balance
Corticospinal tracts: path of Ventral corticospinal tract
Origin in Cerebral Cortex
- Motor areas
- Sensory areas
- Anterior Cingulate gyrus
- Frontal, parietal, & limbic lobes)
Pass uninterupted through deep cerebrum & brainstem to spinal cord
Ventral Corticospinal Tract
- 10-15% of fibers
- Immediately descend in ipsilateral anterior funiculus
- Decussate at the level the tract ends
- Ends on spinal motor neurons in ventral horn
Name the Corticospinal tracts:
Two of them
Lateral Corticospinal Tract
Ventral Corticospinal tract
Vestibulospoinal tract: Medial vestibulospinal tract path
- –Arises from neurons in medial vestibular nucleus
- –Descends bilaterally to in anterior funiculus of the spinal cord
- Where it ends was not listed, but I think it is in the cervical regeion
Tracts that descend at least partially bilaterally
Medial Vestibulospinal Tract (bilateral)
Both Reticulospinal tracts
- Lateral reticulospinal tract (more bilateral)
- Medial reticulospinal tract (more ipsilateral
•Two reticulospinal tracts:
–Lateral (medullary)
–Medial (pontine)
Name the 8 major descending tracts:
Corticospinal tracts (also called pyramidal tract)
- Lateral corticospinal tract (1)
- Ventral Corticospinal tract (2)
Rubrospinal tract (3)
Vestibulospinal Tracts
- Medial vestibulospinal tract (4)
- Lateral vestibulospinal tract (5)
Reticulospinal tracts
- Medial Reticulospinal tract (6)
- Lateral reticulospinal tract (7)
Tectospinal tract (8)
Corticospinal tracts: origin
Origin in Cerebral Cortex
Motor areas
Sensory areas
Anterior Cingulate gyrus
Frontal, parietal, & limbic lobes)
Pass uninterupted through deep cerebrum & brainstem to spinal cord
•Lateral Reticulospinal Tract: Path
- –Arises from nuclei in medullary reticular formation
- –Descends bilaterally but primarily ipsilaterally
- he said we really think of it more as a bilateral tract (???)
- –Descends the length of the spinal cord in anterolateral funiculus
- has Polysynaptic connections that Inhibit motoneurons going to postural muscles
Tectospinal tract: pathway
- •Arises superior colliculus
- •Decussates immediately to descend in anterior funiculus to innervate cervical interneurons & motoneurons
The tectospinal tract Arises superior colliculus and Decussates immediately to descend in anterior funiculus to innervate cervical interneurons & motoneurons.
