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84 Cards in this Set

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What regulates motor circuits in the spinal cord?
Input from descending motor pathways.
What 3 types of structures in the brain control motor circuits in the spinal cord?
1. Cortical structures
2. Subcortical structures
3. Brainstem
3 Cortical structures:
-Primary motor cortex
-Prefrontal cortex
-Somatosensory and parietal association cortex
3 Subcortical structures:
-Basal ganglia
-Cerebellum
-Thalamus
2 Main pathways that motor systems are classified into:
1. Lateral motor pathway
2. Medial motor pathway
What are the 2 Lateral Motor Pathways?
1. Lateral corticospinal tract
2. Rubrospinal tract
How many Medial Motor pathways are there?
5
What are the 5 Medial Motor Pathways?
1. Anterior corticospinal tract
2. Medial Vestibulospinal tract
3. Lateral Vestibulospinal tract
4. Tectospinal tract
5. Reticulospinal tract
What is the function of the Lateral Corticospinal tract?
Movement of contralateral limbs
What is the function of the Rubrospinal tract?
Movement of contralateral limbs
What is the function of the Anterior corticospinal tract?
Control of bilateral axial and girdle muscles
What are the 2 functions of the Medial Vestibulospinal tract?
1. Coordination of eye movements with each other
2. Vestibulo-ocular reflex
What is the function of the Lateral Vestibulospinal Tract?
Balance and posture
What is the function of the Tectospinal tract?
Coordination of head and eye movements
What is the function of the Reticulospinal tracts?
Posture
Where does the Lateral Corticospinal Tract originate from?
-Primary motor cortex
-Frontal areas
-Parietal areas
Where does the Lateral Corticospinal Tract decussate?
Pyramid
Where does the Lateral Corticospinal Tract terminate?
Along the entire spinal cord
Where does the Rubrospinal tract originate from?
Red nucleus
Where does the Rubrospinal tract decussate?
Ventral tegmental decussation
Where does the Rubrospinal tract Terminate?
In the cervical spinal cord
Where does the Anterior corticospinal tract originate?
-Primary motor cortex
-Supplementary motor cortex
Where does the Anterior corticospinal tract decussate?
It doesn't
Where does the Anterior corticospinal tract terminate?
-Cervical spinal cord
-Upper thoracic spinal cord
What is the function of the Anterior corticospinal tract?
Control of bilateral axial and girdle muscles.
Where does the Medial Vestibulospinal Tract originate?
-Medial vestibular nucleus
-Inferior vestibular nucleus
Does the Medial Vestibulospinal Tract decussate?
no
Where does the Medial Vestibulospinal Tract terminate?
Cervical spinal cord
What is the function of the Medial Vestibulospinal Tract?
-Coordination of eye movements with each other
-Vestibulo-ocular reflexes
Where does the Lateral Vestibulospinal tract originate?
In the Lateral Vestibular nucleus.
Where does the Lateral Vestibulospinal tract terminate?
In the entire spinal cord
What is the function of the lateral vestibulospinal tract?
Balance and posture
Where does the tectospinal tract originate?
In the superior colliculus
Where does the tectospinal tract decussate?
In the dorsal tegmental decussation
Where does the tectospinal tract terminate?
In the cervical spinal cord.
What is the function of the Tectospinal tract?
Coordination of head and eye movements
Where does the Reticulospinal tract originate?
In the pontine and medullary reticular formation
Where does the Reticulospinal tract terminate?
Along the entire spinal cord.
What is the function of the Reticulospinal tract?
Posture
Patient is having problems with eye movements - irregularities; where's the lesion likely?
Near CN III -> Midbrain
Patient is having problems with chewing/muscles of mastication or facial expression; where's the lesion likely?
Pons
Patient is having problems with tongue movements; where's the lesion likely?
Medulla (hypoglossal)
Medial motor pathways are located in the ___ funiculus and control ____.
-Located in Anterior funiculus
-Control muscles in the proximal trunk and neck
Lateral motor pathways are located in the ___ funiculus and control ____.
-Located in Lateral funiculus
-Control distal limb
What Medial motor pathway does not extend all the way to the spinal cord? (2 names)
Corticonuclear tract.
Aka, Corticobulbar tract.
What does the corticonuclear tract control?
Cranial nerves that have motor function - muscles of the head, face, and neck.
Where do corticonuclear fibers originate?
In the Precentral gyrus (motor cortex)
How do corticonuclear fibers project to brainstem cranial nerve nuclei?
They pass with Corticospinal tract fibers thru Corona radiata, internal capsule, and cerebral peduncles.
What is the nature of Corticonuclear projections?
Bilateral
Easy way to remember that Corticonuclear projections are bilateral:
You speak and swallow with BOTH sides of the pharynx/larynx.
Exceptions to the bilateral rule for the Corticonuclear tract:
CNs 7 and 12 - project to the contralateral side.
Where does the Corticonuclear tract terminate?
In Brainstem motor nuclei of cranial nerves
What cranial nerve nuclei recieve input from the corticonuclear tract?
V, VII and XII(contralateral), IX, X, and XI.

5, 7, 9, 10, 11, 12
CN V trigeminal controls:
muscles of mastication
VII controls:
muscles of facial expression
XII controls:
tongue
sternocleidomastoid/trapezius:
Spinal accessory - XI
Pharynx/larynx
IX and X
What is the combined nucleus for IX and X?
Nucleus ambiguus
What types of fibers are contained within the corticobulbar tract?
Both DIRECT corticobulbar fibers, and indirect corticoreticular fibers, both coming from the Precentral gyrus.
What are the fibers of the corticobulbar and corticoreticular tracts?
Upper motor neurons - they influence the CN motor nuclei.
What nuclei recieve DIRECT corticobulbar fibers?
-Trigeminal
-Facial
-Hypoglossal
(5, 7, 12)
What are the fibers of the cranial nerves?
LOWER MOTOR NEURONS going to the muscles that they'll innervate.
Are isolated Corticobulbar lesions common?
No; it's generally pretty rare to have an isolated corticobulbar lesion.
When does a unilateral lesion of the corticobulbar tract become clinically significant?
When looking at the Facial and Hypoglossal nerves
What innervates the upper portion of each facial nucleus?
Both corticonuclear tracts - bilaterally.
What innervates the lower portion of each facial nucleus?
The contralateral corticonuclear tract.
What does the upper facial nucleus control?
The upper facial movements
What does the lower facial nucleus control?
The lower facial movements
Does the corticonuclear tract run by itself?
No; it runs with the corticospinal tract that innervates lower motor neurons.
So what deficit would result from a lesion of the RIGHT corticonuclear tract?
A LEFT lower quadrant of the face, and LEFT side of body motor deficit.
What types of central lesions would affect both the corticonuclear and corticospinal tracts?
Cortical lesions
OR
Internal Capsule lesions
What deficit would result from a lesion of the RIGHT facial nucleus or peripheral nerve?
The entire RIGHT side of the face would be paralyzed.
Common cause of a corticospinal / corticonuclear tract lesion:
Stroke in internal capsule
What is a peripheral nerve injury called?
Bell's palsy
How are the hypoglossal nuclei (right and left) innervated?
By the contralateral corticonuclear tract.
So what would happen if you lesioned the left corticonuclear tract?
The tongue would deviate to the right, because the right hypoglossal nucleus would be damaged.
So to what side does the tongue deviate if one of the hypoglossal nuclei is lesioned?
To the same side of the nucleus; bc the opposite muscle is unopposed and pushes the tongue to the that side.
What happens if you lesion the hypoglossal NUCLEUS or peripheral nerve?
It will deviate to the SAME side as the lesion.
What is pseudobulbar palsy?
A BILATERAL lesion of the corticobulbar tract that causes UPPER MOTOR NEURON deficits.
What is Bulbar palsy a problem with?
LOWER motor neurons.
4 symptoms of pseudobulbar palsy:
-Dysphagia
-Dysarthria
-Paresis of the tongue
-loss of emotional control
3 causes of pseudobulbar palsy:
-Brainstem infarcts
-ALS
-MS
What disease is a disease of both UMNS and LMNS and so you'd see pseudobulbar palsy in it?
Lou Gherig's - ALS