Motor Systems Flashcards
What is the basal ganglia and frontal cortexs actions in the hierarchy ?
Deciding and initiating a task
All senses project into these structures
What is the pathway for functional hierarchy of motor systems?
General strategy - plan - build a motor programme - execution of a programme - movement - end point
What is the function of the cerebellum and primary motor area in the hierarchy of motor output ?
Reaching
Proprioceptors, vision and hearing project into cerebellum and colliculus to localise reaching
What is the function of the primary motor cortex in the hierarchy of action ?
It’s involved in grasping and actually carrying out the activity
Skin, joints and muscle project into M1 and reticular formation for manipulation of grasp
What is the direct pathway from the motor cortex to spinal cortex ?
Primary motor cortex and medial and lateral Premotor cortex to lateral part of the ventral horn
- this is to initiate movements of distal limbs
What is the indirect pathway from the primary motor cortex to spinal cortex ?
Primary motor cortex and medial and lateral Premotor cortex to reticular formation to medial parts of ventral horn
- to make postural adjustments which support movement
What is the purpose of the descending upper motor neurons from basal ganglia to motor cortex ?
Planning, initiating and directing voluntary movements
What is the purpose of the descending upper motor neurons projection to the BRAINSTEM centres ?
For basic movement and postural control
What are the main functions of brain in motor control?
Initiation, integration and coordination
What are the main functions of the spinal cord in motor movements ?
Simple reflexes, coordination, pattern generation and integration
How are the motor systems organised ?
In hierarchical and parallel arrangements
This ensures that the motor output doesn’t fail
What areas do the Premotor areas directly control ?
Primary motor cortex
BRAINSTEM
Spinal cord
What are the 3 cortical pathways ?
Lateral corticospinal tracts - skilled limb movements
Ventral corticospinal tracts- axial muscle control
Corticobulbar tracts - controls facial muscles, jaw muscles, muscles for speaking and swallowing
What are the 4 BRAINSTEM motor pathways ?
Rubrospinal tract - originates in red nucleus and is involved in limb control
Tectospinal tract - originates in superior colliculus and is involved in head-eye coordination during gaze
Reticulospinal tracts involved in many autonomic movements and posture
Vestibuli spinal tracts - posture and balance
What pathway only terminates on motor neurons in humans and primates ?
Corticospinal
What is a motor unit ?
Motor neurones associated with their muscle fibres creating a functional entity
How do motor units vary ?
Size
Amount of tension produced
Speed of contraction.
Degree of fatigability
Where motor neurons which innervate axial and distal musculature located ?
Axial- located medially
Distal - located laterally
In motor control why do we have a feedback system and what structure is involved in this ?
Takes into account any errors and the cerebellum is involved
Ensures that a task is carried out meaningfully
What do alpha motor neurons innervate ?
Skeletal muscle
What is a motor neuron pool ?
Collection of alpha motor neurons that innervates a single muscle
What are the 3 inputs to lower motor neurons ?
1- dorsal root ganglion cells with axons to innervate muscle spindle to provide feedback on muscle length
2- upper motor neuron inputs from motor cortex and BRAINSTEM for initiation and control of voluntary movements
3- interneurons in the spinal cord which can be excitatory and inhibitory and these generate spinal motor programmes
Describe fast motor units
Rapidly fatiguing white fibres
Alpha motor neurons are bigger with large diameters for fast conduction
Describe slow motor units
Slowly fatiguing red fibres
Alpha motor neurons are smaller with smaller diameters for slower conduction
What are muscle spindles ?
They are proprioceptors
They have group 1a sensory axons wrapped around their centre to detect stretch of the muscle - this is important feedback because it stops the muscle tearing
Group 1a axons fire more when muscle is stretched