Motor pathways: Cortical motor function, basal ganglia and cerebellum Flashcards
What is the difference in function between the higher and lower cortical areas of the brain?
Higher areas program and coordinate tasks, lower order areas execute tasks
What is the pyramidal tract composed of?
Corticospinal tract
Corticobulbar tract
What makes up the extrapyramidal tract?
Cerebellum
Basal ganglia
Where is the M1?
Pre-central gyrus
What is the function of M1?
Fine, discrete, precise voluntary movement
Describe the layers of M1
6 layers
Layer 5 has Betz cells = very large pyramidal cells
Explain the mapping of M1 and the relevance to stroke
Somatotopic - Penfield’s homunculus
Stroke affecting MCA –> upper limb dysfunction
Stroke affecting ACA –> lower limb dysfunction
Recall the pathway taken by 90% of descending motor neurons
M1 internal capsule cerebral capsules pyramids decussation lateral corticospinal tract ventral horn *synapse with alpha neuron* ventral root spinal nerve musculature
Recall the pathway taken by descending motor neurons that do not decussate in the medulla
M1 internal capsule cerebral capsules pyramids anterior corticospinal tract ventral horn *synapse with alpha neuron* *cross side* ventral root spinal nerve AXIAL musculature
What is the main difference between the corticospinal and corticobulbar tracts?
Corticobulbar = CRANIAL nerves Corticospinal = spinal nerves
What is the function of the premotor cortex and where is it located?
Anterior to M1, regulates externally cued movements
What is the role of the supplementary motor cortex? Recall 3
- Planning of complex movements
- Movement sequences
- Speech mechanics
Recall the 2 association motor cortices
- Posterior parietal
2. Prefrontal
What is the function of each of the association motor cortices?
- PP = ensures movements are targeted accurately to objects in external space
- PF = selects appropriate movements for particular course of action
Recall 2 negative signs of an upper motor neuron lesion
Paresis
Plegia
Recall 5 positive signs of an upper motor neuron lesion
- Babinski’s sign
- Clonus
- Increased muscle tone (spasticity)
- Hyper-reflexia
- Apraxia
What is clonus?
Abonormal oscillatory muscle contraction
What are the most common causes of apraxia?
Stroke or dementia
Dysfunction of which lobes are most likely to result in apraxia
Inferior parietal or frontal
What is apraxia?
Disorder of skilled movement
How does the presentation of a lower motor neuron lesion differ from that of an UMN lesion?
- Decreased tone and reflex speed
- Muscle atrophy
- Fasciculations
- Fibrillations
What is a fasciculation?
Visible twitch due to motor unit damage