Topic 9: Descending control Flashcards
where does the ventromedial pathway travel?
ventral funiculus
What are tracts in ventromedial pathway?
vestibulospinal
tectospinal
reticulospinal
anterior corticospinal
What are tracts in lateral pathway?
lateral corticospinal
rubrospinal
What tract have this function: axial, limb & eye; balance & eye movements?
vestibulospinal
What tract have this function: proximal muscles; movement & posture?
reticulospinal & anterior corticospinal
What tract have this function: distal limb muscles; skilled movements?
lateral corticospinal
What does rubrospinal tract do?
activate proximal arm flexors
What does tectospinal tract innervate?
This tract is responsible for ________?
neck muscles
head orienting movements
Input of rubrospinal tract?
Input of tectospinal tract?
cerebellum & cortex
visual, somatosensory & auditory information
What are the subcortical motor systems?
all tracts except corticospinal
Where does the lateral pathway travel?
lateral funiculus
Where is the origin of rubrospinal tract?
Decribe pathway of rubrospinal tract? (bilateral/unilateral/ipsilateral/ contralateral)
red nucleus
unilateral & contralateral
What tract is rubrospinal tract adjacent to?
lateral corticospinal tract
What is the origin of tectospinal tract?
superior colliculus
Describe the pathway of tectospinal tract
(bilateral/unilateral/ ipsilatera/ contralateral) ?
unilateral & contralateral
Where is the origin of reticulospinal tract?
pontine & medullary reticular formation
what is reticular formation?
networks of neurons that run the length of brainstem
Of all the pathways in descending control, which one doesn’t receive input from cortex?
vestibulospinal
Describe the pathway of pontine reticulospinal tract (bilateral/unilateral/ ipsilatera/ contralateral) ?
Describe the pathway of medullary reticulospinal tract (bilateral/unilateral/ ipsilatera/ contralateral)
unilateral/ ipsilatera
what does pontine reticulospinal tract excite/inhibit? Is it inhibited or excited by higher center?
upper flexors & lower extensors
inhibited
What does medullary reticulospinal tract excite/inhibit? Is it it exhibited or excited by higher center?
excite upper flexors & inhibit all extensors
excited
How does reticulospinal tract support the premotor & motor cortex innitiate movement?
activate the proximal musculature to stabilize & prepare the body for these limb movements
What is the origin of vestibulospinal tract? Where is the input does it receive from?
vestibular nuclei
spiral ganglion via CN 8
Describe the pathway of medial vestibulospinal pathway (bilateral/unilateral/ ipsilateral/ contralateral) ?
bilateral via medial longitudinal fasciculus
What tract does also involve in cardiovascular & respiratory control, sleep & wakefulness functions?
reticulospinal tract
What does medial vestibulospinals pathway activate?
motor neurons & interneurons that innervate neck and back muscles
CN 3,4 & 6 nuclei for eye movement
Describe lateral vestibulospinal pathway (bilateral/ unilateral/ ipsilateral/ contralateral) ?
unilateral & ipsilateral
What does lateral vestibulospinal pathway specifically excite/ inhibit?
excite extensor motor neurons
inhibit flexor motor neurons of the limbs
Name all of the vestibulorspinal reflexes
vestibulo-ocular reflex
vestibulo-cervical reflex
vestibulo- spinal reflex
What does vestibulo-ocular reflex allow you to do?
to gaze fixedly on an object when the head turns
What does vestibulo-cervical reflex allow you to do?
maintain head position by activating neck muscles
What does vestibulo-spinal reflex allow you to do?
maintain balance & posture
Corticobullar pathway is projection of motor cortex neuron to _____?
the brainstem
Brainstem motor neurons project to facial musculature via ______?
cranial nerves
Corticospinal pathway is the projection of motor cortex neuron to _____?
spinal cord
Spinal cord motor neurons project to body musculature via ______?
spinal nerves
Why do we refer lateral corticospinal pathway as “the corticospinal pathway” ?
because it comprises of 90% of corticospinal pathway
ventral corticospinal comprises only 10%
Where is the upper motor neurons in both corticospinal & corticobullar tract?
cortex
T/F: Upper motor neurons in the cortex descend through grey matter to make synaptic connections in spinal cord
False
its cortical white matter
Symptoms of lower motor neuron lesions
muscle weakness
reflexes are reduced or gone
decreased muscle tone, fasiculation & fibrilation
muscle atrophy/ paralyzed
Where is the lower motor neurons for corticospinal tract?
ventromedial funiculus & dorsalateral funiculus of spinal cord
Where is the lower motor neurons for corticobullar tract?
cranial nerve nuclei & other structures of brainstem regions
Describe the pathway of corticalspinal tract
1) axons of motor cortex neurons descend as corona radiata
2) form internal capsule when travel deeper to cortex in diencephalon & telencephalon
3) travel through ventral surface cerebral peduncles & as a bundle at pons
4) continue on ventral surface of medulla as pyramids
5) cross to the contralateral side at medullary/spinal junction as pyramidal decussation (not all cross)
6) in spinal cord, pyramid decussation = lateral corticospinal tract while uncrossed fibers are ventral corticospinal tract
In spinal cord, lateral corticospinal tract make synapse contacts in _______?
dorsolateral funiculus
In spinal cord, ventral corticospinal tract makes synaptic contact in _______?
ventromedial funiculus
decerebrate rigidity
the postures of upper limbs & lower limbs are both extended
where is the lesion to cause decerebrate rigidity?
btw mesencephalon & pons
Why does decerebrate rigidity occur?
lateral vestibulospinal continue to excite extensors
decorticate regidity
the posture disease in which upper limbs flexes & lower limbs extends
Where is the lesion to cause decorticate rigidity?
above nuclei
Why does decorticate rigidity occur?
rubrospinal tract continue to excite
What does proximal muscles involved in?
balance, posture & preparation of movement
What does distal muscles involved in?
voluntary movements (Ex: movements of digits)
What is the other name for pontine reticulospinal tract?
What is the other name for medullary reticulospinal tract?
medial reticulospinal tract
lateral reticulospinal tract
What tract is responsible for following situation: When you hear a bang & see something flying through air from the same direction, this pathway is responsible for orienting you head & eyes toward stimuli
Tectospinal tract
motor equivalence
the brain represent the outcome of action independently on specific effectors used or the specific way the action is achieved
What tract innervate CNs 3,4 & 6 for eye movements?
medial vestibulospinal tract
What tract is responsible for following situation: gastrocnemius is activated first when person is instructed to “pull on the bar as soon as you hear the bell” in anticipation of the arm movement
reticulospinal tract
How is voluntary movements different from reflex movements?
VM requires input from cortex vs RM requires input from spinal cord/ brainstem
generated internally vs generated only in response to stimuli
organized around performance of task vs stereotyped
practice & learning improve the effectiveness of voluntary movements vs same every time
Where is the primary motor cortex?
T/F: Motor map of primary motor cortex (M1) is different from the map of somatosensory cortex
precentral gyrus
False.
What tract that excites upper flexors but inhibit all extensors ?
medullary (lateral) reticulospinal tract
What are the symptoms of upper motor neurons lesions?
muscle weakness
spasticity (clonus, hyperactive reflexes, increased tone)
Babinski’s sign
loss of fine voluntary movements
When there is a stroke or tumor in brain, what will happen to cause UMN symptoms?
What tract that excites upper flexors & lower extensors and inhibited by higher center?
pontine (medial) reticulospinal tract
What is the concept explaining the following example: I can write my name with my toes, left hand, right hand or teeth.
motor equivalence
What tract that excite all extensors & inhibit all flexors of the limbs indirectly through interneurons?
lateral vestibulospinal tract
spasticity
What is the cause?
the strong resistance to passive movements of the limb
due to the hyperactive stretch reflex
What are two pathways that involve in spasticity?
medial reticulospinal tract
vestibulospinal tract
What does premotor cortex involve in?
movement planning
How does lateral premotor cortex (LPC) differ from supplementary premotor cortex (MPC)?
LPC=observing an action movement that we are about to do vs MPC = imagining a complex movements
triggered by external sensory stimuli vs generated internally
spasticity is the result of ______ (increase/decrease) _______ (excitation/ inhibition) inputs
from medial reticulospinal & vestibulospinal tracts
increase
excitation
Where does the premotor cortex receive inputs from?
multisensory inputs from inferior & superior parietal lobe
inputs relating to motivation & intention from prefrontal cortex
