Movement the motor system jun 13 2014
This presentation is the property of its rightful owner.
Sponsored Links
1 / 51

Movement & the Motor System Jun 13, 2014 PowerPoint PPT Presentation


  • 119 Views
  • Uploaded on
  • Presentation posted in: General

Movement & the Motor System Jun 13, 2014. SENSORIMOTOR CONTROL. From Sensory to Motor. Sensory info -- guide motor system Somatosensory, vestibular, visual Book works from the TOP to BOTTOM Sensory “ up”, motor “ down” Here -- SIMPLE to COMPLEX . Organization. HIERARCHY

Download Presentation

Movement & the Motor System Jun 13, 2014

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Movement the motor system jun 13 2014

Movement & the Motor SystemJun 13, 2014


Sensorimotor control

SENSORIMOTOR CONTROL


From sensory to motor

From Sensory to Motor

  • Sensory info -- guide motor system

    • Somatosensory, vestibular, visual

  • Book works from the TOP to BOTTOM

    • Sensory “up”, motor “down”

  • Here -- SIMPLE to COMPLEX


Organization

Organization

HIERARCHY

  • Analogy to a corporation

    • Workers = muscles

    • Supervisors = spinal cord & brainstem

    • Quality control = basal ganglia & cerebellum

    • Manager = primary cortex

    • President/CEO = higher order cortex


Movement the motor system jun 13 2014

When do you use your motor system?


Movement the motor system jun 13 2014

What is actually “moving” in the “motor system” … ?


Motor units

MOTOR UNITS


Muscles

Muscles

  • Skeletal muscle - stability to bony skeleton

  • Move around axes

  • 1000s of muscle fibers

    • “Fast” twitch fibers – speed

    • “Slow” twitch fibers – endurance


Muscles1

Muscles

  • Innervated by motor neurons from spinal cord

    • ACh (neuromuscular junction)

  • Motor unit – motor neuron & muscle fibers

  • Receptors for proprioception

    • Ch. in length (stretch), tension


Muscles2

Muscles

  • Only actively contract - more than one direction depends on antagonistic pairs

    • Contraction/relaxation

    • Ex. biceps & triceps

  • Flexorsbend, extensorsstraighten


Spinal circuits

SPINAL CIRCUITS


Spinal cord

Spinal Cord

  • Via motor neurons

  • Sensory feedback from muscle & somatosensory

  • Can be independent of the cortex

    • Basic reflex circuits

    • Copy of information to cortex

    • Quick, unconscious


Basic motor reflexes

Basic Motor Reflexes

Withdrawal reflex

Sensory info  spinal cord  motor response

“Walking” reflex

In response to foot contact, ankle rotation

Infants


Basic motor reflexes1

Basic Motor Reflexes

Stretch reflex

  • After sudden stretching force

  • Muscle stretch receptor  spinal cord muscle

  • Compensatory contraction

  • Controls external force on body position

    Infant reflexes

  • Sucking, rooting, grasping, startle


Basic motor reflexes2

Basic Motor Reflexes

  • Requires info to muscle contracting, antagonist, and contralateral

    • Adjust and coordinate both sides


Reflexes

Reflexes

  • Some directed by brainstem

    • Eye movements (saccades, smooth pursuit)

      Complex movement under control of the cortex and descending motor pathways


Motor cortex

MOTOR CORTEX


Primary motor cortex

Primary Motor Cortex

Most “movement” requires cortical control

Cortex to motor neurons (spinal cord) & brainstem

Directed movement, interaction with the environment


Primary motor cortex1

Primary Motor Cortex

  • Pre-central gyrusof frontal lobe

    • Adjacent to somatosensory area (post-central gyrus)

    • Why is this relevant?

  • Homunculus

    • Fingers, tongue, face – fine motor control


Descending pathways

Descending Pathways

  • Several tracts

  • Different tracts/locations  different motor deficits

  • Control of posture/whole body movements vs. limb movements


Descending pathways1

Descending Pathways

Dorsolateral corticospinal tract

  • Distal muscles (limbs, hands, fingers, etc.)

  • Primary motor cortex medulla (crossover)  spinal cord  muscles


Descending pathways2

Descending Pathways

Three other tracts…

  • Indirect to spinal cord

  • Synapse w/ cranial nerve motor info

  • Proximal trunk muscles

    1o cortex receives info from secondary motor cortex


Movement the motor system jun 13 2014

When does the motor system need to be suppressed?


Basal ganglia cerebellum

Basal Ganglia & Cerebellum


Basal ganglia

Basal Ganglia

  • Interconnected nuclei

  • Communicates w/ midbrain, rest of cortex

  • Distribution of tone, coordinating muscle groups

    • Shifting weight, posture

  • Cognitive roles

    • Compulsion, motivation, reward


Cerebellum

Cerebellum

  • Comm. w/ cortex, basal ganglia, brainstem

  • Corrects movements, motor errors

    • Based out output

  • Rapid movement req. fine control, adapting to changing conditions

  • Also has cognitive roles


Higher order motor control

Higher Order Motor Control


Secondary motor cortex

Secondary Motor Cortex

Premotor cortex

  • Frontal lobe

  • To primary motor

  • Decisions, coordination, programming of motor plans (sequence of events)

    • Order of movements, patterns

    • Imagining action


Secondary motor cortex1

Secondary Motor Cortex

  • Complex integration of secondary areas

    • Input about target, body position

  • Mirror neurons – observation of motor action

    • Social learning & cooperation

  • Input from association cortex (in prefrontal cortex)


Association cortex

Association Cortex

  • Dorsolateral prefrontal cortex

  • Project to premotor area

  • Control over motor system

    • Directing attention, eye movements

    • Decision to make movements

    • Sensory feedback


Association cortex1

Association Cortex

  • General programs stored, adapted to situations

  • Can be developed w/out practice

  • Can be modified w/ practice

    • Group behaviors together

    • Shift control to lower hierarchy (less cortex)


Motor system dysfunction

Motor System Dysfunction


Motor dysfunction

Motor Dysfunction

At any point in the hierarchy

  • Muscle weakness, atrophy, paralysis

    • Communication betw. spinal cord & motor unit

  • Descending pathways

    • Motor control, coordination, etc.

    • Cerebellar or basal ganglia disorders


Motor dysfunction1

Motor Dysfunction

  • Apraxia – dysfunction in voluntary movement

    • Not due to muscle, comprehension, motivational deficit

  • Reappearance of infant reflexes w/ cortical damage (withdrawal, grasping)

    • Don’t “outgrow” them, inhibited w/ development


Huntington s chorea

Huntington’s Chorea

  • Basal ganglia & cortex

  • Genetic case - autosomal dominant

    • 30-50 years old

    • Protein damages neurons, over-stimulates target cells

    • Death of neurons

  • Severe cognitive, motor dysfunction

  • Jerks, twitches, writhing (dancing movements)


Parkinson s disease

Parkinson’s Disease

  • Death of neurons proj. to basal ganglia

    • Substantianigra

  • Rigidity, tremor, slowed movement; cognitive

  • Starting, stopping voluntary motion

  • Genetic, environmental causes


Parkinson s disease1

Parkinson’s Disease

Treatment – replace DA

  • DA can’t cross BBB

  • L-Dopa to replace DA

  • Neurons continue to die

  • Serious side effects


The frozen addicts

The Frozen Addicts

Awakening the Frozen Addicts (BBC, 1993)

http://youtu.be/QJIMC9d9l2o

MPPP (synthetic opioid)


Movement the motor system jun 13 2014

MPTP

Ingestion of MPTP causes severe, immediate Parkinson’s symptoms…

…What is the mechanism?


Movement the motor system jun 13 2014

MPTP

  • MPTP metabolized to MPP+ by MAO enzyme

  • MPP+ brought into cells – DA reuptake transporter

  • Selective for neurons in substantianigra

    • Neurotoxic


Movement the motor system jun 13 2014

MPTP

  • Implications for control of movement?

    • SN projects to basal ganglia (putamen/caudate)

  • Animal models

    • Primates

    • Some rodents (rats are immune)

  • MPP+ toxicity as a natural cause of Parkinson’s?


  • Login