Learning Objectives 1. Describe the Functions/Components/Deficits of the motor system (table) 2. Explain the difference between upper and lower motoneurons 3. Describe the roles of the Basal Ganglia and Cerebellum in control of movement https://nba.uth.tmc.edu/neuroscience/s3/chapter01.html Christopher Cohan, Ph.D. Dept. of Pathology/Anat Sci Jacobs School of Medicine
From Sensation To Movement What is Different about Movement Sensory systems require constant attention for perception. Movement is automatic. It is learned and then it occurs without need for conscious control. This allows us to attend to many other tasks while we move. Reflexes are unlearned, automatic responses. In the spinal cord, they depend upon local circuits formed developmentally and do not require the brain (eg withdrawal, postural adjustment, deep tendon reflex). Clinical tools!
What s Involved in Movement Motor system is much more complex than sensory system: Multiple components and pathways involved Each pathway has complex features Each pathway controls a specific aspect of movement These pathways act simultaneously during a movement
What s Involved in Movement Plan - what s moving (eg GPS) Start - get it going from rest (eg car starter) Move - some rhythmic (eg car engine) Adjust/Coordinate uphill, downhill, fast, slow Sensory feedback Speed, direction, amplitude, force Maintain balance/posture don t fall It all happens simultaneously and without much thought
Movement Control FUNCTION COMPONENT DEFICITS Start Basal Ganglia Spontaneous movement Move (Plan) Understanding the type of deficit is KEY to identifying the motor component involved in lesion. Upper/Lower Motoneurons Weak/Paralyzed Plan Cerebellum Ataxia (jerky) Adjust Cerebellum Ataxia/Inaccurate Coordination uncoordinated Balance Cerebellum Falling/Nystagmus. Download the Template for Motor Systems to help organize this information.
How We Move 1. Perform the movement Like the ENGINE of your car cortical motor area One on each side
How We Move Signals for movement travel from: 1. Brain to spinal cord 2. Spinal cord to muscles
How We Move Involves 2 components with a relay (connection) in the spinal cord Brain (corticospinal tract) Spinal cord (spinal nerves) Muscles
How We Move upper motor neurons A 2 tier system: 1. Brain The Boss creates the plan and activates it 2. Spinal cord the employee just does what it s told to do lower motor neurons This distinction is important because it recognizes the different functions explains different symptoms when each component is damaged
How We Move upper motor neurons Serious consequences if damaged Weakness or NO movement lower motor neurons
UMN are not sufficient to control all the complex operations involved in movement. Two additional helpers are needed: basal ganglia cerebellum Their effect is simple - adjust UMN activity
1. Helps get things started: Basal Ganglia increases upper motoneuron activity (think of the starter motor on a car) idea action Consequences of damage (starter on car doesn t work or stuck on) Starting - difficult Stopping - never
How We Move Adjust/Coordinate uphill, downhill, fast, slow Sensory feedback Adjust speed, direction, amplitude, force after the movement starts Maintain balance don t fall cerebellum
How We Move Adjust/Coordinate uphill, downhill, fast, slow Sensory feedback Adjust speed, direction, amplitude, force after the movement starts Maintain balance don t fall Consequences of damage - ATAXIA (loss of coordination) loss of accuracy, smoothness of movement, appropriate force, balance cerebellum
Upper/Lower Motoneurons Thalamus Cerebral Cortex Basal Ganglia Cerebellum corticobulbar head muscles LMN Brainstem UMN corticospinal body muscles Spinal Cord
Motor Components Helper #1 Cerebral Cortex Thalamus Basal Ganglia Cerebellum head muscles Brainstem body muscles Spinal Cord
Motor Components Helper #2 Cerebral Cortex Thalamus Basal Ganglia Cerebellum head muscles Brainstem body muscles Spinal Cord
Take-Home Message UMN/LMN perform the movement. Without that there is no movement. Other parts of the system build on that. The 2 helpers adjust UMN activity: Basal Ganglia start the movement Cerebellum coordinates the movement