Unit 3 Flashcards
(62 cards)
What are the three elements of voluntary movement?
1) Target Identification/ Intent
2) Programming and planning
- praxic=how, handled in cerebral cortex
- intentional-when, function of basal ganglia and cerebellum
3) Execution, midcourse corrections done through cerebellum
Describe the differences between upper and lower motor neurons.
1) Upper motor neurons exist entirely in the CNS and control the activity of LMNs
2) Lower motor neurons have cell body in CNS, axons go into PNS to form motor end plates on skeletal muscles
What are the five areas of the cortex that deal with motor information?
- primary motor cortex (M-I)
- premotor cortex
- supplementary motor area
- frontal eye fields
- posterior parietal motor area
Primary Motor Cortex general info and functions.
- contains Brodmanns area 4
- neurons in layer 5 give rise to corticospinal tract
- primarily controls fine distal movements
- individual, simple movements, well defined
- direction controlled by a population of neurons, not a single UMN
- kept informed of limb position and speed through communication with S-1 and area 5 of PMA
What happens if there is damage to the Primary Motor Cortex?
-upper motor neuron signs, lack of fine distal movements (piano/guitar playing)
Premotor Cortex general info and functions.
- includes lateral Brodmanns area 6
- primary input from parietal lobe (PMA)
- small output to CST and reticular formation
- for more complex movements, slower than M-I ex: movement of entire limb
- plays role in planning movements, setting the stage
- integrates external stimuli such, visual, auditory to help movement
- dorsal PMC=reaching, ventral PMC=grasping
- mirror neurons
Supplementary Motor Area general info and functions.
- includes medial Brodmanns area 6
- complex movements
- coordination of movements on both sides of the body (proximal and distal muscles with CST), can do so without visual cues
- functions in mental imaging of movements
- stores learned motor programs
What happens if there is damage to the PMC?
- no paresis
- apraxia of complex tasks
- perseveration
What happens if there is damage to the SMA?
- no paresis
- difficulty coordinating movements on both sides
- difficulty learning new motor movements
Posterior Parietal Motor Area general info and functions.
- includes Brodmanns areas 5 and 7
- major role in correlating external world with body position and motivation
- modulated by state of attention, driven by goal oriented activities
- functions in sensorimotor transformations
What happens if there is damage to the PMA?
- no paresis
- apraxia
- difficulty with hand orientation
- astereognosia and agraphesthesia
Voluntary Motor Control Pathways general facts
1) monosynaptic (bineuronal): directly from cortex to LMN
2) fast, uninterrupted pathways
3) ends contralateral
- corticospinal and corticonuclear: for realization of movements (fine movements)
Corticospinal tract
Start: in one of the motor cortical areas
- fibers course somatotopically, heads down to spinomedullary junction
- here 85-90% of fibers decussate into lateral funiculus to become lateral corticospinal tract (LCST) while the other fibers DONT decussate and enter ventral funiculus to become ventral (anterior) corticospinal tract (ACST)
- eventually get to anterior commissure and end in LMN
- NOTE: all fibers end contralateral
Lateral Corticospinal Tract
activates motor neurons controlling distal musculature particularly hands/feet, fingers/toes
Ventral (anterior) corticosinal tract
-activates neurons that innervate axial musculature
Corticonuclear Tract
Start-in motor cortex areas
- synapse in cranial nerves
- some terminate in midbrain (CN 3, 4)
- some terminate in pons (5,6, 7)
- some terminate in medulla (9,10,11,12)
- bilateral with the exception of facial expression (7) and tongue muscles (12)
Extrapyramidal System
- indirect pathway, multineuronal
- for involuntary movement and synchronization of movement
- includes rubrospinal tract, vestibulospinal tract, and reticulospinal tract
Rubrospinal Tract
- starts in red nucleus of midbrain, decussate, go to lateral funiculus in spinal cord and end in LMN in ventral horns
- primarily influences flexor muscles and acts as a supplement to corticospinal
- so if lesion in corticospinal, animal still has some movements, but not the fine distal movements
Vestibulospinal Tract
- both a medial and lateral
- start in vestibular nuclei, head to ventral funiculus and end in ventral horns
- mediators of postural adjustment and head movements
Reticulospinal Tract
1) Lateral: from reticular formation to ventral horns and it bilateral. INHIBITS motor neurons that innervate extensor muscles
2) Medial: from reticular formation to ventral horns and is ipsilateral. EXCITES motor neurons that innervate extensor muscles
Tectospinal Tract
- Starts in superior colliculus, end in ventral horn of cervical spinal cord only
- primarily functions in reflex control, also coordinates head/neck/eye movement in response to environmental stimuli
Functions of Basal Ganglia
- coordination and planning of voluntary movements
- thought to play a role in scaling the amplitude and velocity of movements
Basic Basal Ganglia general facts
1) corpus striatium=caudate, putamen, and globus pallidus
2) Striatum=caudate and putamen
3) lentiform nucleus= putamen and globus pallidus
- most inputs are to the striatum
- most outputs are from the globus pallidus
The Basal Ganglia connections are all ____.
ipsilateral