Motor Tracts Flashcards
What areas of the brain are dedicated to motor planning and coordination?
basal ganglia
cerebellum
motor association areas
Descending pathways include:
corticospinal
corticobulbar
bulbospinal
What is an example of a local neuronal network?
central pattern generator
Area 4 is known as
primary motor cortex (MI)
Area 6 is known as
motor association areas
Premotor cortex (PMC) is located:
rostral to primary motor on lateral hemisphere
Supplemental Motor Cortex (SMA or MII) is located:
rostral to primary motor on medial hemisphere
Somatotopic organization of ventral horn means trunk/axial musculature is located:
most medially
Somatotopic organization of ventral horn means hip/shoulder girdle musculature is located:
intermediate
Somatotopic organization of ventral horn means distal limb musculature is located:
most laterally
flexors = dorsal
extensors = ventral
Lateral motor system is more associated with
distal limb
fine motor control
Medial motor system is more associated with
girdle and trunk
gross motor control (i.e.: walking and postural adjustment)
The lateral motor system involves these 2 tracts:
- lateral corticospinal
2. rubrospinal
The medial motor system involves these 4 tracts:
- anterior corticospinal tract
- medial and lateral vestibulospinal tracts
- medial and lateral reticulospinal tracts
- tectospinal tract
A unique feature of lateral corticospinal tract is
fractionation of limb movements
The lateral corticospinal tract is also known as
pyramidal tract
Describe lateral corticospinal tract origin
50% from primary motor (area 4)
50% from supplementary (area 6), premotor, somatosensory (area 1,2,3) and other areas of parietal cortex
How many axons in lateral cortico-spinal tract?
approx 1 mil
The majority of axons in lateral cortico-spinal tract are ____ myelinated.
finely myelinated
Approx ____% of fibers in lateral cortico-spinal tract cross in the ______.
90%
caudal medulla
Most axons of lateral cortico-spinal tract synapse with LMNs @ what location?
contralateral spinal cord
The fibers of the lateral cortico-spinal tract course from the ______ and then to the posterior limb of the _____.
corona radiata
internal capsule
The fibers of the lateral cortico-spinal tract course through the ____ in the midbrain.
crus cerebri
The fibers of the lateral cortico-spinal tract course through smaller fascicles in the ____.
basilar pons
The fibers of the lateral cortico-spinal tract course through the ____ as the pyramids.
medulla
The fibers of the lateral cortico-spinal tract terminate in the ____.
lateral ventral horn
Describe the functions of the lateral cortico-spinal tract (4)
- fine motor control of distal musculature
- facilitates motor neuron pools of all muscles
- deliberate, isolated, fractionated movements
- innervates hands and feet
______ tract is the only tract that innervates the hands and feet.
lateral cortico-spinal tract
The _____ tract is the red nucleus in the midbrain that decussates.
rubrospinal
The rubrospinal tract terminates on?
contralateral lateral anterior horn in HAND regions
The rubrospinal tract innervates ____.
UE flexors
The anterior corticospinal tract is composed of approx ___% of the corticospinal fibers.
8%
The anterior corticospinal tract fibers descend _____.
ipsilaterally
Where do the anterior corticospinal tract fibers cross?
at the level of the cord where they terminate
Where do the anterior corticospinal tract fibers terminate?
contralateral innervation of medial aspect of ventral horn (with some bilateral innervation)
What is the fxn of the anterior corticospinal tract?
axial and girdle muscular control
Which tracts provide major influence over extensors of trunk and girdle?
medial and lateral vestibulospinal tracts
The medial and lateral vestibulospinal tracts innervate:
ipsilateral limb for equilibrium response
The fxn of the medial vestibulospinal tract is:
head/eye coordination, head orientation
bilateral innervation
The fxn of the lateral vestibulospinal tract is:
equilibrium response and extensor activation during stance phase of walking (primarily ipsilateral innervation)
The medial vestibulospinal tract only goes to the ____ cord.
cervical
The medial reticulospinal tract is from the ____.
pons
The lateral reticulospinal tract is from the ____.
medulla
The reticulospinal tracts descend in the:
ventral and lateral funiculi of the SC
The reticulospinal tracts descend _____.
bilaterally
The reticulospinal tracts terminate in the:
medial portion of the anterior horns
The medial reticulospinal tract induces excitation of ___ and inhibition of ___.
+ extensors
- flexors
The lateral reticulospinal tract induces excitation of ___ and inhibition of ___.
+ flexors
- extensors
The reticulospinal tracts are important in
reciprocal movements required for walking, postural control responses
The tectospinal tract runs through the:
superior colliculus in the midbrain
then decussates
The tectospinal tract innervates contralateral _____.
neck extensors and eye muscles
The tectospinal tract is involved in orientation of
head and eyes
turning them to contralateral visual stimuli
What are the 2 functions of the corticobulbar tracts?
- voluntary control over brainstem area
2. adaptation of automatic responses as a result of experience/learning
Where do corticobulbar tracts terminate in the brainstem?
- cranial nerve nuclei
- motor areas of the brainstem (vestibular, reticulospinal, tectospinal tracts)
- sensory relay nuclei
- reticular formation
The ________ tracts are the cortical innervations of the brainstem.
corticobulbar
Corticobulbar fibers descend in the ______ just anterior to corticospinal fibers.
internal capsule
Corticobulbar fibers go through crus cerebra and exit at the:
level of brainstem where they do their innervating
Bulbar signs (AKA cortical stroke) include difficulty with ….
feeding, swallowing, dysphagia
With MCA stroke, recovery of _______ > recovery of _____.
trunk/girdle > hand/foot
bilateral innervation versus unilateral innervation
There is predominantly contralateral innervation by cortex even though the ______ system has significant bilateral innervation.
lateral
What is the role of the primary motor cortex?
(area 4)
- deliberate, fractionated, isolated movement of individual joints in specific directions
- facilitate all motor neuron pools
What is the role of the supplemental motor cortex?
- generates pattern of movement involving multiple segments, trunk
- internally generated mvments
- active in mental rehearsal of moment
- assemble motor programs or routines
- ipsilateral innervation
What is the role of the premotor cortex?
- generates movemnt pattern in response to external stimuli
- includes inputs also to hand and distal limb motor neurons
- involved in reaching and grasping with visual guidance
Premotor cortex receives input from posterior parietal cortex via the dorsal visual stream for what fxn?
reaching and grasping with visual guidance
LMN always refers to:
alpha MN in SC
UMN refers to:
neurons in other parts of CNS that drive the LMN
UMN lesion usually results in ______.
spasticity
LMN lesion always results in ______.
hyporeflexia
Babinski sign (plantar response) indicates:
corticospinal lesion
What is a normal (-) response to babinski test?
toe flexion
What is an abnormal (+) response to babinski test?
any amount of extension
A “bulbar sign” is any clinical sign related to:
brainstem fxn (particularly cranial nerves)
MCA cortical stroke often results in:
contralateral hemiparesis (aka hemiplegia/hemianesthesia)
MCA stroke characteristics:
less contralateral activation
distal muscles most affected, trunk least affected
gross movement patterns (synergies)
loss of fractionated mvmnt
initially present with bulbar signs which usually resolve
UE is usually ____ dominant and LE is usually _____ dominant with MCA synergies.
UE: flexion
LE: extension
Decorticate posturing:
remove cortex (rubrospinal tract intact) extension of LE and flexion of UE
Decerebrate posturing:
midollicular (below red nucleus)
extension of UE and LE
IR and plantar flexion
Explain why UE and LE have similar posturing with decerebrate rigidity:
extension throughout due to dominant influence of vestibular system
