NS: Central Motor System Flashcards
Where do the UMN arise in?
- Cerebral cortex
- Brainstem
What do the UMN synapse with?
- LMN
- Interneurons
What is activity adjusted by?
- Basal Ganglia (9)
- Cerebellum (10)
Name the 3 types of tracts that control mov’t
- postural/gross mov’t
- selective motor control
- nonspecific
What are the muscles controlled in the Postural/gross mov’t tract?
- antigravity muscles
- groups of limb muscles
What are the muscles controlled in the selective motor control tract?
isolated contractions of individual muscles in limbs
What are the muscles controlled in the nonspecific tract?
facilitates all LMN
What does the UMN synapse with in the Postural/gross mov’t tract?
Where does the UMN synapse in the ventral horn?
- LMN to multiple muscles
- Medially
What does the UMN synapse with in the selective motor control tract?
Where does the UMN synapse in thee ventral horn?
- LMN that innervate specific muscles
- interneurons that inhibit LMN of unwanted muscles
- Laterally
What does the UMN synapse with in the nonspecific tract?
Where does the UMN synapse in thee ventral horn?
- background levels of excitation in cord
- facilitate local reflex arcs
- throughout
What column of the spinal cord does the medial UMN tract descend in?
Anterior column of the spinal cord
- Resticulospinal
- Medial & lateral vestibulospinal
- Medial corticospinal
Name the function of the Reticulospinal tract
Medial UMN tract (postural/gross mov’t)
- Anticipatory mov’ts - bilateral activation
- Muscle synergies
many locations - trunk, neck, proximal muscles of the limb
what are Muscle Synergies?
- Activation of a group of muscles to achieve a specific task
- Flexor or extensor synergies of the limb (modified by lateral corticospinal tract)
- Coordinating trunk with proximal limb muscles during walking
Where does the medial & lateral vestibulospinal tracts synapse?
Medial UMN tract (postural/gross mov’t)
Medial: bilateral cervical & thoracic spinal cord
Lateral: Ipsilateral flexors & extensors
what are the movements elicited in the medial & lateral vestibulospinal tracts?
Medial UMN tract (postural/gross mov’t)
medial: neck and upper back muscles
laterea: facilitate extensors, inhibit flexors
what are the functions of the medial & lateral vestibulospinal tracts?
Medial UMN tract (postural/gross mov’t)
medial: coordinate head & eye mov’t
lateral: maintain posture & balance
Where does the medial corticospinal tract originate?
Medial UMN tract (postural/gross mov’t)
Cerebral cortex
which muscles are impacted in the medial corticospinal tract?
Medial UMN tract (postural/gross mov’t)
neck, shoulder, trunk muscles
wha is the function of the medial corticospinal tract?
Medial UMN tract (postural/gross mov’t)
Voluntary muscle control
- the only medial tract that starts in the cortex and is responsible for voluntary control**
why is the nonspecific tract known as the emotional motor system?
it tends to be active when theres intense emotions
e.g., mov’t is more conservative when standing at a high platform vs low platform (fear of falling)
Where does the lateral corticospinal tract synapse?
Lateral UMN tract (selective motor control)
- LMN that innervate single muscle
- interneurons that inhibit muscles
what mov’ts are elicited in the lateral corticospinal tract?
Lateral UMN tract (selective motor control)
- Wrist & hand extension
- Ankle & toe dorsiflexion
- Selective motor control throughout limbs
What is unique about the Lateral corticospinal tract?
Lateral UMN tract (selective motor control)
- It is the most important pathway for voluntary mov’t
- after a stroke this tract cana predict how much mov’t will recover
- The only tract that can control the most distal parts of our body**
- e.g., provides precisee selective control of the hand & fingers
True or False: All of the lateral corticospinal tract axons cross contralaterally
False - MOST do (80-90%) cross contrallaterally, 10% still descend ipsilaterally
What are broadmann areas 4 and 6?
4 - primary motor cortex
6 - premotor cortex
What is broadmann area 46? function?
Prefrontal - working memory, location of objects in space to guide mov’t
describe the function of broadmann areas 5 & 7
posterior parietal - integration of multiple sensory modalities
Describe the function of M1
the motor command to the muscles - signal/coding to move
Describe the function of the lateral premotor cortex
creates motor plan for mov’ts in response to an external cue (monkey example -> lights were used)
Describe the function of SMA
Creates a motor plan for mov’ts that are generated from memory (internal cue)
What is the function of the lateral dorsal premotor area?
Division of lateral premotor area
- planning/influence motoro control for learned association mov’ts
- learned aassociations between arbitrary cues & motor response
What is the funciton of the lateral ventral premotor area?
Division of Lateral Premotor area
- Planning/influence motor control of hand movements for manipulation of objects
- Planning movements guided by visual information about object properties
in a study done on monkeys, what did they discover in the lateral ventral premotor area?
Mirror neurons - firing both when performing an action and observing another indivdiual performing that action
what is the function of the Cingulate Motor area?
Suggested role in motor selection based on reward evaluation
What are impairments associated with a lesion to M1 (UMN signs)
Paresis/weaknesses
Poor coordination
Moving in synergies
Substitution/compensation
Hypertonia/hyperflexion
Low fast twitch (type II) MU
Increased size of remaining MU
what are the impairments associated with a lesion to premotor areas?
- inability to respond to external stimuli
- Apraxia
What is apraxia?
Inability to produce a familiar goal directed mov’t, but capacity to move is intact
- e.g., using the flipping motion of a spatula but in the wrong plane (video showed lady flipping it to her face)
VS ataxia –> they can carry out the mov’t but with little coordination
- e.g., flipping an egg with spatula with very shaky mov’ts
