Motor Systems Flashcards
Which type of musculature is regulated by the LCST?
Proximal (arms, hands, legs)
Which type of musculature is regulated by the ACST?
Distal (trunk)
Which two descending tracts are highly localized in the internal capsule?
Corticospinal and corticobulbar tracts
What descending tract takes up the most space in the IC?
Corticopontine
Where does the corticobulbar tract originate?
Cortical areas related to head and face
Where does corticobulbar tract terminate
Brainstem nuclei (bilateral)
What is the VL thalamus involved in?
Motor integration (involved in feedback loops via pons, cerebellum, dentate gyrus, and red nucleus)
What are the two divisions of the corticospinal tract?
1) Lateral CST; 2)Anterior CST
What is the target function of efferents originating in the ACST?
Postural adjustment
What is the target function of efferents originating in the LCST?
Skilled movement of extremities
Which somatotopic portion of the LCST is supplied most by the POSTERIOR spinal arteries?
the Cervical (most medial) > thoracic > lumbar > sacral; all are supplied by both the posterior and anterior spinal arteries
Describe the somatotopic preservation of motor fibres travelling through the posterior IC
(Arms most rostral, legs most caudal)
What proportion of the crus cerebri (anterior midbrain) is devoted to descending motor fibres?
The middle 3/5ths
In what portion of the brainstem does the corticospinal tract travel as pyramids?
Rostral/anterior medulla
What proportion of the the corticospinal tract fibres remain uncrossed at the level of the caudal medulla?
10-15% – form ACST
Where do fibres in the ACST cross the midline?
SC at the level where they terminate on their LMNs
Descending UMNs form the __ before converging in the posterior limb of the IC
Corona radiata
Where are the UMNs for the corticobulbar tract?
Head and face regions of the primary motor cortex (precentral gyrus)
Which cranial nerve motor nuclei do fibres from the cortical bulbar tract terminate on bilaterally
1) Nucleus ambiguus; 2) Hypoglossal nucleus; 3) facial motor nucleus ROSTRAL region (upper facial muscles)
Which 2 cranial nerve motor nuclei do fibres from the cortical bulbar tract terminate on NOT bilaterally (exceptions to bilateral innervation)
1) Spinal accessory nucleus (ipsi projections for sternomastoid, contralateral for trapezius); 2) Facial motor nucleus (contralateral innervation to caudal part of nucleus (lower facial muscles)
Where does the corticobulbar tract descend in the IC?
At the genu
Where do fibres of the corticopontine tract originate?
Frontal, parietal, and temporal lobes
Which limbs of the IC does the corticopontine tract descend in?
Anterior AND posterior limbs
Which proportion of the crus cerebri is devoted to the corticopontine tract?
Lateral and medial 1/5
Where does corticopontine tract terminate?
Pontine nuclei
Where do the post-synpatic neurons of the corticopontine tract cross the midline?
In basal pons as TRANSVERSE PONTINE NUCLEI in the pontocerebellar tract
Where does the pontocerebellar tract terminate?
Contralateral cerebellar hemispheres
Which cerebellar peduncle is associated with the pontocerebellar tract?
Middle CP
Where do fibres of the dentarubrothalamic tract originate?
Dentate nucleus of cerebellum
Where do efferent fibres of the dentarubrothalamic tract exit the cerebellum?
Superior cerebellar peduncle
Where do fibres of the dentarubrothalamic tract cross the midline?
Caudal midbrain
Where do fibres of the dentarubrothalamic tract terminate?
Red nucleus and VL/VA thalamus
Where do fibres of the dentarubrothalamic tract travel after reaching the thalamus (VA/VL)
Motor cortex via posterior limb of IC - provide a copy of descending motor info
Which two modulatory motor tracts originate in the dentate nucleus?
1) Dentatorubrothalamic tract; 2) Dentatothalamic tract
Primary function of the vestibulospinal tract?
Influence postural changes to compensate for body and head movements
Which muscle types are influenced by the LATERAL vestibulospinal tract?
Extensors
Name 2 afferents to the vestibular nuclei
Cerebellum and inner ear (vestibular nerve)
Describe path of lateral vestibulospinal tract
1) Lateral vestibular nuclei –> ipsi brainstem tegmentum –> ipsi ventrolateral white matter columns –> terminates on ipsilateral interneurons in anterior gray horn of spinal cord at all levels
Where do fibres in the lateral vestibulospinal tract terminate?
Ipsilateral interneurons in anterior gray horn of spinal cord at all levels
Which muscles are influenced by the medial vestibulospinal tract?
Neck and axial
Where does the medial vestibulospinal tract descend?
1)Bilaterally through medulla near tectospinal tract and medial lemniscus 2)In anterior white column of spinal cord
Where does medial vestibulospinal tract terminate?
Interneurons in anterior gray horn, primarily in cervical and thoracic levels
Which fibre bundle connect the nuclei of CNs III (occulomotor), IV (trochlear), and VI (abducens)
Medial longitudinal fasciculus (MLF)
Where does the reticulospinal tract orginate?
Scattered RF nuclei in tegementum of the pons and medulla
Where do reticulospinal tract fibres terminate?
interneurons in anterior gray horn
From pons, what is the output of the reticulospinal tract
descending fibers located medially in brainstem - provide inhibitory input to gamma motor neurons
From medulla, what is the output of the reticulospinal tract?
descending fibers located laterally in brainstem - provide excitatory input to gamma motor neurons
What is the function of the rubrospinal tract?
Faciltate flexor and inhibit extensor muscle activity
Where does the rubrospinal tract originate AND decussate
Red nucleus in midbrain; receives afferents from cortex and cerebellum (via SCP)
Where does rubrospinal tract terminate?
Interneurons in anterior gray horn of spinal cord
What type of neurons does reticulospinal tract act on?
reticulospinal tract acts on α motor neurons, supplying trunk and proximal limb muscles to influence locomotion and postural control, and muscle tone (via γ motor neurons)
Where does the tectospinal tract originate?
Superior colliculus of midbrain
Where do tectospinal fibres terminate?
the cervical spinal cord where they innervate contralateral motor neurons responsible for neck movements
What is the role of the tectospinal tract?
Orienting the head and neck during eye movements.
What 5 types of information does the cerebellum receive?
1) proprioceptive information from spinocerebellar and cuneocerebellar tracts; 2) muscle tone and activity of spinal reflex arcs (spinocerebellar and cuneocerebellar tracts), 3) position of the head (vestibular information), 4) cortical activity (sensory, motor, and association areas), and 5) information from the environment (visual and acoustic).
