6.4 Descending Motor Pathways Flashcards
What does the pre-frontal cortex do?
Makes the cognitive decision to perform a motor task
What does the posterior parietal cortex do?
provides information about the world and the body
Provides sensory guidance
What does the pre-motor/ supplementary motor areas do?
Sequence actions
What does the primary motor cortex do?
execute actions for a motor program
What do the primary somatosensory area and posterior parietal cortex do?
Provide continual updates during the task
What do the caudal, rostral, lateral ad medial areas of M1 do?
Caudal: brings limbs towards body
Rostral: Reaching
Lateral: face becomes involved
Medial: legs
What happens during training of a new task?
The region involved with that task will become larger so will have a larger cortical representation
Where do sensory inputs converge?
Posterior parietal cortex
What do lesions in the PPC cause?
neglect of body or the outside world, body integrity identity disorder
What is the neural activity in the PPC dependent on?
The goal of the activity - highly active when reaching/searching/manipulating an object but otherwise silent for goaless hand gestures
What is the role of the lateral pre-motor cortex?
Prime M1 for motor actions
Coordination of both sides of the body
Code for intention to execute the appropriate motor behaviours in response to an external event
What regions of the lateral PMC are involved in performing and imagining a task?
BA6 and 4 for performing and BA6 only when imagining
What are the rostral/ventral areas of lateral PMC?
Brocas area - speech production
What elicits the SMA?
Thought to be evoked by internal cues (memory)
Where does SMA have its output?
M1
Where do the corticospinal fibres originate?
M1, SMA, PMA, S1
How do the corticospinal fibres descend?
Through the corona radiata, internal capsule, cerebral peduncles, pass through the pons, enter the pyramids on ventral aspect of the medulla
80% decussate to form lateral C/S
10% descend in ipsilateral lateral C/s
10% form the anterior C/S tract
What does the corticospinal tract control?
input to motor neurones that innervate skeletal muscle - especially flexors
What does the crticobulbar tracts control?
The motor nuclei of the cranial nerves
How do the corticobulbar fibres descend?
Originate from cells in the head and face region, descend through corona radiata then medial part of the internal capsula. Enter the cerebral peduncles medial to corticospinal tract, synpase bilaterally onto motor nuclei
Which corticobulbar tract does not have ipsilateral innervation?
Lower facial nucleus
What is the role of the rubrospinal tract?
Provide innervation to the upper limb flexors
Where do fibres for the rubrospinal tract begin and terminate?
Red nucleus and terminate in the Rexed region V-VIII of the cervical spinal cord
What is the role of the reticulospinal tract?
Pontine/medial: activates spinal reflexes of antigravity muscles
Medullary/lateral: Inhibits antigravity muscles
