Motor Pathways (Quiz 6) Flashcards
LMNs are also known as?
GSEs
Which lamina are found in the ventral horns and have motor functions?
lamina 8 and 9
What are the other names for association cortex?
supplementary motor cortex and premotor cortex
What are the 5 descending pathways?
1) corticospinal tract
2) reticulospinal tract
3) rubrospinal tract
4) vestibulospinal tract
5) tectospinal tract
Which 2 pathways are the mediators of voluntary movement?
corticospinal tract and reticulospinal tract
Where are the UMNs for the corticospinal tract?
primary motor cortex
Where are the UMNs for the reticulospinal tract?
reticular formation
Where are the UMNs for the rubrospinal tract?
red nucleus (midbrain)
Where are the UMNs for the vestibulospinal tract?
vestibular area
Which pathway is responsible for postural adjustments and head movements?
vestibulospinal tract
Where are the UMNs for the tectospinal tract?
tectum (roof of midbrain, from the superior colliculus)
Which pathway starts from the superior colliculus and is responsible for head movements?
tectospinal tract
Descending pathways can be classified based on 2 things. What are they?
1) somatotopic organization (lateral vs medial motor systems)
2) voluntary or involuntary (pyramidal vs extrapyramidal)
note: extrapyramidal means the axons go through the tectum instead of pyramids
Lateral motor systems travel in the ____________ columns of the spinal cord. They synapse on more laterally located motor neurons, in the ventral horn of the spinal cord
lateral
Medial motor systems descend in the ________________ aspect or ___________ columns of the spinal cord
anteromedial, ventral
The lateral motor system includes what tracts?
1) lateral corticospinal tract
2) rubrospinal tract
Which tract is responsible for voluntary movement of the limbs?
lateral corticospinal tract (LCST)
Which tract augments that activity of the flexor muscles and inhibits the action of the extensor (antigravity) muscles?
rubrospinal tract
The medial motor system (axial or medial muscles for balance, posture, and coordination) includes what tracts?
1) anterior corticospinal tract (ACST)
2) vestibulospinal tract
3) reticulospinal tract
4) tectospinal tract
Which tract controls the voluntary movement of the axial and girdle muscles?
anterior corticospinal tract (ACST)
Which tract controls body balance?
vestibulospinal tract
Which tract regulates the function of spinal reflexes and maintains muscle tone when standing and walking?
reticulospinal tract
Which tract is responsible for the blinking reflex and eye pursuit movements when following an object?
tectospinal tract
Even though corticospinal, rubrospinal, reticulospinal, and vestibulospinal fibers are able to influence LMNs and their local connections, this still does not explain how a voluntary movement is made. _____________ areas of cortex “decide” that a movement is called for. _________ areas of the cortex devise a plan for the movement and pass this info on to the motor cortex which will issue commands to motor neurons either directly or indirectly. The basal nuclei and cerebellum are involved in various aspects of planning and monitoring movements but have few or no outputs of their own to the spinal cord- they act primarily by affecting motor and premotor cortex
Association, Premotor
Where is the UMN for the LCST?
primary motor cortex
What is the largest motor tract in the human body?
LCST
What are the other names for the LCST?
lateral corticospinal tract or pyramidal tract
The LCST/pyramidal tract is a large crossed, descending tract that contains approx. 85% of fibers from the _____________ pyramid that cross in the __________________
contralateral, pyramidal decussation
In the spinal cord, the LCST is located in the __________ half of the __________ funiculus, medial to the posterior spinocerebellar tract
posterior, lateral
Where do the fibers of the LCST originate, pass through, and terminate in?
test q
1) cerebral cortex (in the precentral gyrus and nearby areas)
2) descend through the internal capsule
3) through cerebral peduncle (midbrain)
4) basal pons
5) medullary pyramid (anterior medulla)
6) decussate at the spinomedullary junction (pyramidal decussation)
7) travel down spinal cord (C1 down) in tthe lateral funiculus to the appropriate spinal level
8) ends in the ventral horn or intermediate gray matter. They terminate on the motor neurons of the ventral horn (lamina 8 or 9)
Where are the UMNs for the ACST?
primary motor cortex
The 15% of fibers in each pyramid that do not cross in the pyramidal decussation continue into the _________ funiculus as the _________
anterior, ACST
The ACST fibers terminate on motor neurons or interneurons in medial portions of the _________ horn or intermediate gray matter, so they preferentially affect the activity of motor neurons for _______ muscles
anterior, axial
Most ACST fibers end in __________ and __________ segments, so they may have a special role in the control of neck and shoulder muscles (for keeping head upright)
cervical, thoracic
The LCST is ipsilateral in the cerebrum, midbrain, pons, and medulla. It crosses the _____________ and is contralateral in the spinal cord. It exits in the ventral roots of the same side, mainly to _______________
caudal medulla, distal muscles
Is the ACST a voluntary or involuntary pathway?
voluntary
The ACST is ipsilateral in the cerebrum, midbrain, pons, and medulla. It is also ipsilateral in the spinal cord. Where does it cross?
in spinal cord and exits the contralateral ventral root
The ACST exits to what muscles?
axial muscles, mostly cervical and thoracic segments
What 2 tracts are the pyramidal tracts?
ACST and LCST
Where are the UMNs for the corticobulbar tract?
primary motor cortex
What is another name for the corticobulbar tract?
corticonuclear tract
What does bulbar mean?
brainstem
Does the corticobulbar tract go to spinal cord?
no it stops at the brainstem
The corticobulbar tract activates the motor nuclei of?
cranial nerves
The corticobulbar tract innervates skeletal muscles of the…
head/face
The corticobulbar fibers descend to _________ and ____________ levels where most of them terminate in the reticular formation to synapse with interneurons. These interneurons synapse with LMNs in the cranial nerve motor nuclei. A number of fibers terminate directly and bilaterally in the motor nuclei of the ____________ and _____________
pontine, medullary, trigeminal CN V, facial nerve CN VII
What cranial nerves are involved in the corticobulbar tract? Which motor nuclei are involved?
CN 5, 7, 9, 10, 11, and 12
motor nucleus of CN V, facial nucleus, hypoglossal nucleus, and nucleus ambiguous
The corticobulbar tract does not project to the motor nuclei of the oculomotor, trochlear, and abducens nerves. These nuclei review motor signals from the ______________ indirectly
cerebral cortex
What does extrapyramidal mean?
axons do not go through the pyramids
Where do the fibers of the rubrospinal tract originate?
red nucleus (UMNs are here)
The red nucleus contains a lot of what to give it a pale pink color?
Fe + ferritin
The red nucleus is in the _____________ of the rostral midbrain at the level of the superior colliculus
tegmentum
For the rubrospinal tract, after leaving the red nucleus, the axons cross to the opposite side. This crossing of nerves occurs just in front of the ___________. After decussation, these axons descend downward as rubrospinal tract on the ____________ side of the spinal cord
red nuclei, contralateral
Which tract helps animals walk and swing with their 4 legs?
rubrospinal tract
Which tract is just lateral to the LCST?
rubrospinal tract
The rubrospinal tract terminates in the ________ horns and facilitates ________ and inhibits the activity of _________ and antigravity muscles
ventral, flexors, extensors
The red nucleus receives afferents from the _________ and the _____________
motor cortex, cerebellum
**cerebellum is the main input
Which tract influences spinal motor neurons?
rubrospinal tract
The corticorubral tract (similar to CST) arises from the sensorimotor cortex (association cortex) and terminates in the ipsilateral red nucleus in the midbrain. The cell bodies in the caudal part of the red nucleus gives rise to fibers forming the larger __________ tract and the smaller __________ tract
rubrobulbar, rubrospinal
note: rubrospinal tract is insignificant in humans
The red nucleus facilitates the the alpha, beta, and gamma motor neurons that innervate the contralateral upper limb ________ muscles, whereas it simultaneously inhibits those of the extensors, specifically the nerve cells that innervate the distal muscles of the upper limbs. This controls the movement of the _______ and _______
flexor, hand, digits
In the rubrospinal tract- the __________ neurons include the neurons present in the motor area of the cerebral cortex as well as neurons of the red nuclei. Aka are supraspinal
1st order
In the rubrospinal tract- the _________ neurons of the rubrospinal tract are internuclei neurons of the spinal cord
2nd order
In the rubrospinal tract- the __________ neurons are the motor neurons
3rd order
The rubrobulbar tract decussates in the __________
tegmentum
What nuclei are a part of the rubrobulbar tract?
-main sensory nucleus of trigeminal n.
-spinal trigeminal nucleus
-facial nucleus
In the rubrobulbar tract, the fibers decussate in the tegmentum and descend and synapse in the main sensory nucleus of the trigeminal, spinal trigeminal, facial nucleus, and lateral RF. From the RF, it can stimulate the ___________ tract which contains ANS fibers from T1-L2. The nucleus cuneatus and gracilis modulate ascending sensory info
reticulospinal
Where is the tectum?
roof of midbrain posteriorly
What is the other name for the tectospinal tract?
colliculospinal tract
The fibers of the tectospinal tract arise from the deep layers of the ______________ (UMNs are here), sweep anteromedially around the PAG and _______________, decussate and descend as the tectospinal tract
superior colliculus, oculomotor nuclei
note: MLF is involved here bc of the eye movements
Where does the tectospinal tract terminate?
in the ventral horns of upper cervical segments
Which tract is responsible for reflex movements of the head and neck to visual stimuli?
tectospinal tract
note: its an extra-pyramidal tract for connecting cervical cord for neck and head movements. The majority of the tectospinal tract fibers terminate in the upper cervical segments
The association areas (Brodmann’s areas _________) give rise to the fibers of the ____________ tract that descend to terminate in the oculomotor accessory nuclei and the deep layers of the superior colliculus
18 and 19, corticotectal
Ganglion cells went to the tectum to give visual info to what tract?
tectospinal tract
The tectospinal tract is involved in the coordination of head movements with eye movements elicited by ________, auditory, or vestibular stimuli
visual
(visual is the major input here!)
Where do the vestibulospinal tract fibers originate?
in the vestibular nucleus
Which CN is involved with the vestibulospinal tract?
CN VIII
Afferents of which tract is received from CN VIII inner ear?
vestibulospinal tract
The vestibular nuclei receives input fibers from the vestibular n., that carries info from the inner ear, and from the cerebellum. Fibers are ________ and descend as the vestibulospinal tract
uncrossed
The __________________ tracy activates limb extensor muscles to maintain the body in an upright posture, in response to accelerations that would otherwise lead to falling
lateral vestibulospinal
Which tract is essential for balance and control of the activity of extensor muscles?
lateral vestibulospinal tract
The medial longitudinal fasciculus (MLF) is a tract that reflexly activates eye muscles and neck muscles to counter acceleration. The cervical portion of the MLF is also known as the….
medial vestibulospinal tract
What are the 2 reticulospinal tracts?
medullary and pontine reticulospinal tract
Which tract arises from the RF present in the medulla and forms the lateral reticulospinal tract?
medullary reticulospinal tract (more flexion than other one)
Which tract arises from the RF present in the pons and forms the medial reticulospinal tract?
pontine reticulospinal tract (keeps you upright)
Extending from the medial zone of the pontine and medullary reticular formations, through the spinal cord, and finally terminating on the limb flexors and extensors, the reticulospinal tract controls locomotion and posture. The fibers are ________, descend through the midbrain, pons, and medulla, and terminates in the _______ horns
uncrossed, ventral
Which 2 tracts influence the motor control of axial (trunk) and proximal limb musculatures and are involved in posture maintenance and orientation of the limbs in an intended direction. Influence muscles involved in voluntary movement and reflex activity
medullary and pontine reticulospinal tracts
Which tract consists of descending autonomic fibers in the lateran horns?
test q
reticulospinal tract
(these autonomic fibers are responsible for controlling some autonomic functions such as heart rate, circulation, breathing, and respiratory rate
The corticoreticular fibers arise from the __________ and supplementary motor area. These fibers synapse bilaterally with the neurons of the medial zone of the pontine and medullary RF. Also have input from the basal ganglia, red nucleus, and substantia nigra via the central tegmental tract, these modulate the activity of the reticulobulbar and reticulospinal neurons
premotor cortex
What does Turn to ViP mean?
T= tectospinal for turning the head
V= vestibulospinal
P= pontine/medial reticulospinal
VP helps with with medial axial muscles
What does Rest on a Mat mean?
R= rubrospinal
M= medullary/lateral reticulospinal
both of these would activate flexors/inhibit extensors to lay down (bc medullary is lateral it can also be used for distal muscles)
What pathway is here?
LCST
What pathway is here?
rubrospinal tract
What pathway is here?
lateral/medullary reticulospinal tract
What pathway is here?
ACST
What pathway is here?
medial/pontine reticulospinal tract
What pathway is here?
tectospinal tract
What pathway is here?
vestibulospinal tract
