Cortical Motor Function Flashcards
What is volition?
Motor systems produce movements that are adaptive and accomplish a certain goal
Describe the hierarchical organisation of motor control.
Association Cortex
Motor Cortex
Brainstem
Spinal Cord
What are postural adjustments and unconscious processing?
Postural Adjustments – the motor system has to compensate for changes in the body’s centre of mass during movements
Unconscious Processing – many of the postural adjustments occur without our awareness
What are the three parts of the motor cortex?
Primary Motor Cortex
Premotor Cortex
Supplementary Motor Area
What makes up the association cortex?
Frontal Cortex and Parietal Cortex
NOTE: this is not exactly part of the motor pathway but it influences the planning and execution of movements
What are the two parts of the pyramidal (descending) system?
Corticobulbar Tract – starts in the cortex then exits and innervates the muscles in the face
Corticospinal Tract – starts in the cortex and exits and innervates the muscles in the arms and legs
Describe the side loops of this descending pathway and their role.
The descending pathway also has two side loops that go to the cerebellum and basal ganglia. The cerebellum and basal ganglia check the motor information before it travels to the muscles and has its effect
Which lobe are the three parts of the motor cortex found in? Describe their arrangement.
Frontal (anterior to the central sulcus) The primary motor cortex is on the precentral gyrus
The premotor cortex and the supplementary motor area are anterior to the primary motor area
What is another name given to the three parts of the motor cortex?
Primary Motor Cortex = Broadmann’s Area 4
Premotor + Supplementary Motor Area = Broadmann’s Area 6
What are the most important cells in the primary motor cortex?
Betz Cells (pyramidal cells)
Where are Betz cells located within the grey matter and which tracts originate from here?
They are found in the 5th layer of grey matter, the corticospinal tracts originate from here
Describe what happens to the upper motor neurones that come from the primary motor cortex.
Travel through brainstem to pyramidal decussation in medulla - 95% of the axons cross midline.
These axons continue down the spinal cord and synapse with a lower motor neurone and exit into a peripheral nerve to the reach the skeletal muscle.
The pathway of the corticobulbar tract similar– Upper motor neurones go down into brainstem and synapse with lower motor neurone and they exit to the facial muscles
What are the two types of descending pathway?
Lateral and Medial
Which tracts are lateral? Which are medial?
Lateral
Lateral corticospinal tract
Rubrospinal tract
Medial Anterior corticospinal tract Reticulospinal tract Vestibulospinal tract Tectospinal tract (Colliculospinal tract)
What is the function of lateral and medial pathways?
Lateral = Control of proximal and distal musculature, voluntary movements or arms and legs Medial = Control of axial muscles, balance and posture
Describe the structure and function of the lateral corticospinal tract.
Lateral corticospinal tract originates in M1 from the Betz cells.
Axons pass through brainstem, decussate at the pyramidal decussation in the medulla.
Then passes down spinal cord and synapses with a lower motor neurone.
It goes onto control mainly the distal musculature.
NOTE: 95% of axons from primary motor cortex decussate at medulla, the 5% that don’t decussate form the anterior corticospinal tract.