Motor system III Flashcards
Which part of brain causes the execution of movements?
primary motor cortex
(although almost all cortical areas input)
These cells are from which motor tract? [1]
Primary motor cortex –> corticospinal tract
Define hemiplagia [1]
loss of voluntary movements on the contralateral side of the body
What makes a region a watershed region in the brain? [1]
Region supplied by both the MCA and ACA: means that if stroke occurs can compensate
Which artery supplies most of the lateral surface of the frontal, parietal and temporal lobes? [1]
MCA
Which arteries do the arrows point to? [1]
Lenticulostiate arteries
Label 5, 6 & 7
1 - superior temporal gyrus;
2 - inferior frontal gyrus; 3 - insular cortex;
4 - temporal stem;
5 - internal capsule;
6 - thalamus;
7 - lentiform nucleus (the internal and external globus pallidus and the putamen)
8 - frontal horn;
9 - superior circular sulcus;
10 - inferior circular sulcus.
The MCA is divided into different segments. Label A-C that depicts this.
A: M1: horizontal section
B: M3: cortical section
C: Sylvian section
Middle cerebral artery:
Describe the difference between an occlusion in M1 v M3
M1: supplies blood supply to the basal ganglia via the lenticulostriate arteries & motor cortex. Causes a very bad lesion
M3: Only supplies motor cortex alone - Less bad lesion
Which part of the body would an occlusion to the MCA not effect and why? [2]
Lower limbs are not affected: supplied by ACA
How is the the somatosensory cortex involved in motor control?
40% of corticospinal and corticobulbar tract axons arise from somatosensory cortex; can modulate somatosensory input (e.g. supress nocicpetive pain)
FYI summary
Where does the corticospinal tract cross decussate in the body? [1]
On the way to the brainstem, which structure does the cortiospinal tract pass through? [1]
Decussates in upper spinal cord: C1-C5
Goes through the internal capsule on way to brainstem
Describe an overview of the corticospinal tract [3]
- Primary motor cortex on l/r signal: upper motor neuron travels in brain to medulla where the lateral corticospinal tract decussates; the ventral corticospinal tract will decussate in the spinal cord just before they synapse with lower motor neurons.
- The lateral corticospinal tract controls distal fine muscle movement.
- The ventral corticospinal tract controls axial movement
- After synapsing at the ventral horn, becomes lower motor neuron. leaves spinal cord to innervate muscle motor
The corticobulbar tracts provide innervation to the musculature of which region of the body?
Head and neck
Upper limbs
Lower limbs
Neck
The corticobulbar tracts provide innervation to the musculature of which region of the body?
Head and neck
Upper limbs
Lower limbs
Neck
A lesion of the CST above the decussation of the pyramids will result in deficits on the [] side.
A lesion of the CST below the decussation of the pyramids will result in deficits on the [] side.
A lesion of the CST cranial to the decussation of the pyramids will result in deficits on the contralateral side.
A lesion of the CST caudal to the decussation of the pyramids will result in deficits on the ipsilateral side.
Which part of the body does CST have monosynaptic connections with? [2]
Explain why [1]
How does the CST control movement in other muscles? [1]
Monosynaptic connections with thumb and digits
Creates a greater degree of precision of movement
Other muscles are controlled via CST synapsing on interneurons: modulates spinal reflexes
Which tract controls the movement of the face? [1]
Corticobulbar tract
Explain why forehead sparing can occur from lesion in the UMN of the corticobulbar tract but does not in a LMN lesion.
Forehead has bilateral innervation from the corticospinal tract; if lesion occurs in UMN then the contralateral side can still innervate
Lower part of face is only innervated by one (contralateral nerve): LMN lesion causes contralateral upper and lower paralysis
Extrapyramidal tracts:
What is the role of the reticulospinal tract [1]
Responsible for autonomic control of the sympathetic preganglionic neurons (eg heart rate, circulation, breathing, respiratory rate)
Also provides drive to the respiration via the phrenic nerve)
Extrapyramidal tracts:
Desribe the path of the medial and lateral reticulospinal tracts [2]
Medial Reticulospinal Tract (Pontine): Descends ipsilaterally
Lateral Reticulospinal tracts (Medullary): Descends bilaterally
Extrapyramidal tracts:
Desribe the path of the medial and lateral reticulospinal tracts [2]
Medial Reticulospinal Tract (Pontine): Descends ipsilaterally
Lateral Reticulospinal tracts (Medullary): Descends bilaterally
Extrapyramidal tracts:
What is the role of the lateral vestibulospinal tract? [1]
Controls posture and balance
Extrapyramidal tracts:
Describe the course of the lateral vestibulospinal tract
Fibres descend ipsilaterally though the anterior funiculus of the same side of the spinal cord, synapsing on the extensor antigravity motor neurons
Extrapyramidal tracts:
Desribe the function and path of medial vestibulospinal tract
Function: Performs the synchronization of the movement of the eyes with the movement of the head so that eyes do not lag behind when the head moves to one side
Pathway: Descends bilaterally in the medial longitudinal fasciculus. Synapses with the excitatory and inhibitory neurons of the cervical spine
Describe the function and path of the rubrospinal tract [2]
Function: Controls muscle tone in flexor muscle groups; Inhibits extensor tone
Path:
- Arises from the red nucleus in the brainstem
- crosses at medulla
- terminates primarily in the cervical and thoracic portions of the spinal cord
Path and function of tectospinal tract? [2]
Coordinates voluntary head and eye movements
Involved in both auditory and visual cues, it is primarily understood to orient our eyes and head towards both auditory and visual stimuli. For example, if you were sitting in a quiet room and all of a sudden heard a noise to your right, you would subconsciously turn your head in that direction and orient your eyes towards the direction of the sound, attempting to find the source.
Path:
Originates in the superior colliculus
Projects to the contralateral cervical spinal cord to terminate in Rexed laminae VI, VII, and VIII
Spasticity:
Effect on muscle tone and reflexes ? [1]
Lesion usually occurs where in body? [1]
Spasticity:
* Increased muscle tone and reflexes
* UMN damage
Clonus
Describe the characteristic movements associated with clonus [1]
UMN or LMN lesion? [1]
Lots of jerky contractions followed by a suddent stretch of muscle
UMN lesion
https://www.google.com/search?q=clonus&rlz=1C5CHFA_enGB760GB761&hl=en&sxsrf=AJOqlzUkXZhV4TRE-1FXesUfy9LnZqP-NA:1674751896001&source=lnms&tbm=vid&sa=X&ved=2ahUKEwi-jOT-2OX8AhWuRUEAHcBgBmwQ_AUoAXoECAEQAw&cshid=1674751960915393&biw=714&bih=732&dpr=1#fpstate=ive&vld=cid:596e37d4,vid:4SrhgjGIZ30
Describe how rigidity occurs [1]
If have a lesion above the pons occurs, the inhibitory system is lost; extrapyramidal system becomes hyperactive
Describe the how a patient would present with:
Decorticate posturing [4]
Decerebrate posturing [3]
Decorticate posturing:
* plantar flexed
* internally rotated legs
* flexed hands and elbows
* adducted arms
Decerebrate posturing:
* Plantar flexed
* Pronated hands
* Extended arms
Where would damage occur for the following:
Decorticate posturing [1]
Decerebrate posturing [1]
Decorticate posturing:
* Damage to the corticospinal tract above or in midbrain
Decerebrate posturing
* Damage to the corticospinal tract at the level of upper brainstem, including corticospinal and rubrospinal tracts
