MOTOR SYSTEMS

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MOTOR SYSTEMS

• Muscles and Joints
• Muscles
• Moving
• The Spinal Cord
• Spinal Reflexes
• Reciprocal Control of Opposing Muscles
• Polysynaptic Adaptations and Reflexes
• The Motor Cortex
• The Basal Ganglia
• Limbic System
• The Cerebellum
• Cranial Nerves

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Muscle groups are complex attach bone to bone
via tendons and ligaments
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A muscle group has many fibers
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The Neuromuscular junction (NMJ) The receptive
portion of muscle-the motor end-plate
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The NMJ ( sometimes called the motor end-plate)
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nACHr
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End-plate potential

• Larger
• Longer
• Leads to Ca influx in sarcolema of muscle
• Ca causes muscle contraction

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Disease of the NMJ? MG
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MG
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muscle fibers encase myofibrils. The casing is
called the sarcolema
Muscle group
myofibril
Muscle fiber
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End-plate potential causes ca influx into
sarcolemma
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Myofibrils in turn contain Actin and Myosin
filaments
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When the NMJ is activated Actin-myosin interact
to shorten the length of a muscle fiber
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Sliding filament model of muscular contraction
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Muscle shortenswork
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Cortical vs Spinal control of behavior

• Goal-directed
• Complex
• Higher levels of control
• Plastic
• Numerous reflexive behaviors are involved

• Reflexive
• Simple
• Automatic
• inplastic

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Spinal reflex ARCs

• Monosynaptic
• stretch
• Polysynaptic
• Withdrawal
• Antagonist muscle groups
• Synergistic muscle groups
• Polysegmental relexes
• Cross-spinal reflexes

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A monosynaptic spinal reflex arc- the Stretch
reflex
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The stretch reflex involves neuromuscular
spindles
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Stretch reflex regulates muscle tension in every
muscle group
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The polysynaptic part of stretch reflexes
inhibition of Antagonist muscles
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Spinal inhibition of antagonist muscles require
inhibitory interneurons
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The withdrawal reflex arc a polysynaptic spinal
reflex
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Also involves interneurons
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And may involve more than one spinal cord segment
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And/or Cross spinal reflex arcs
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The Goli tendon organ (GTO) reflex
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Neural activity of spinal neurons related to
whole muscle group activity
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Lower motor neurons the final common pathway
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Goal-Directed Behavior and Reflexive Behavior
Goal-Directed Reflex
Relatively Complex Relatively Simple
Consciousness? Intention Automatic
Plastic Relatively Inplastic
Requires Cortex Cortex not required
Learning /experiences are major influence Genetics are major influence
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Goal-Directed Behaviors Require

• Goal selection and prioritization
• Resistance to distracters
• -Cross-modal Sensory integration
• Perception of target
• Awareness of location of movable body part
• Ability to aim movement of body part
• Ability to detect errors and re-adjust, (use
  feedback)
• Ability to use feedback to control movement of
  body part

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Sensory-Motor Integration in the frontal lobes
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THE DLPFC The conductor
Integrates cross modal input- may initiate
goal-directed behaviors
Lesions of the dorsolateral frontal areas results
in a number of executive motor impairments.
These include perseveration, incoordination,
motor impersistence, apraxias and hypokinesia.
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The premotor and supplementary motor ctx The
sections
Stimulation complex sequences of behavior
(aimless behavior)
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Damage to the secondary Motor Cortex?

• Ideomotor Apraxia
• This apraxia is associated with great difficulty
  in the sequencing and execution of movements. A
  common test of apraxia is to request the patient
  to demonstrate the use of a tool or household
  implement (e.g., "Show me how to cut with
  scissors"). Difficulties are apparent when the
  patient moves the hand randomly in space or uses
  the hand as the object itself, such as using the
  forefinger and middle finger as blades of the
  scissors. They have additional trouble sequencing
  the correct series of movements and make errors
  in orienting their limbs in space consistent with
  the desired action. Imitation of the movements of
  others will usually improve performance but it is
  still usually defective.
• Memories for skilled acts are probably stored in
  the angular gyrus of the parietal lobe in the
  left hemisphere.

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The primary motor cortex the instrument
Stimulation relatively simple fragments of
behavior
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TWO MAJOR DESCENDING PATHWAYS FROM THE PRIMARY
MOTOR CORTEX The Dorsolateral pathway
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And the VM Path.

• The VM pathway does not discretely decussate,
  but does branch and innervate contra lateral
  segments in the spinal cord.

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DL vs VM descending motor paths

• Dorsolateral
• Decussates at medullary pyramids
• Distal muscle groups
• More direct
• More volitional control
• Higher resolution of control

• Ventromedial
• Does not cross
• Medial muscle groups
• Gives off spinal collaterals
• Yoking
• Lower resolution of control

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Other Motor Pathways

• In addition there are other motor paths that have
  relays in the brainstem
• These other paths innervate nuclei of the RAS,
  cranial nerve nuclei, etc

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Descending paths get additional inputs
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Both pathways terminate in spinal cord segments
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According to part of the body they control
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On lower motor neurons (alpha motor neurons)
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Amyotropic lateral sclerosis (ALS)disease of the
alpha motor neurons
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ALS
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Alpha motor neurons project to form part of
spinal nerve pairs
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Terminate on muscle fibers
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At each spinal segment
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BASAL GANGLIA

• Nigro-striatal Pathway
• Striato-Pallidal pathway

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Basal Ganglia

• Neostriatum
• Caudate (kaw-date) nucleus and putamen
  (pew-TAY-men)
• Globus Pallidus ( GLOB-us PAL-i-dos)
• Substantia nigra (included by functional not
  anatomical relationship)
• Subthalamus
• others

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Basal ganglia- Complex ccts
The basal ganglia are involved in motor
regulation, but are only one component of the
control of behavior. The way in which the basal
ganglia controls movement is complicated and not
completely understood, but at his time may be
fairly described as the gate-keeper of movement.
Disorders of the basal ganglia can either lead to
too much behavior or too little behavior.
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Basal Ganglia-Neostriatum ( composed of the
caudate nucleus and the Putamen)
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The Nigro-striatal pathway- the behavioral
grease system
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The Globus Pallidus ( the striato-pallidal
circuit the behavioral brakes system)
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Basal Ganglia Syndromestoo much or too little
behavior

• Damage to the Nigro-striatal pathway
• Parkinsons (not enough behavior)
• http//video.google.com/videosearch?hlenrlsGGIC
  ,GGIC2007-01,GGICenum1qparkinsonsndsp20ie
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• http//video.google.com/videosearch?hlenrlsGGIC
  ,GGIC2007-01,GGICenum1qparkinsonsndsp20ie
  UTF-8saNtabiv

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Basal Ganglia syndromes

• Strato-Pallidal Pathway- too much behavior
• Huntingtons
• Tourettes
• Balisms
• Others

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• Huntington's Chorea is principally characterized
  by hyperkinesias - abnormal, purposeless,
  involuntary motor movements that can occur
  spontaneously or only when the patient is trying
  to do something. These movements may be
  repetitive or non-repetitive.

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Tourettes Syndrome

• TS usually becomes apparent in children between
  ages 2 to 15, with approximately 50 of patients
  affected by age 7. The age of symptom onset is
  typically before the age of 18. TS is more
  frequent in males than females by a ratio of
  about 3 or 4 to 1. The disorder is thought to
  affect 0.1 to 1.0 of individuals in the general
  population.

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Tourettes

• Motor ticsInitially, patients develop sudden,
  rapid, recurrent, involuntary movements (motor
  tics), particularly of the head and facial area.
  At symptom onset, motor tics usually consist of
  abrupt, brief, isolated movements known as simple
  motor tics, such as repeated eye blinking or
  facial twitching. Simple motor tics may also
  include repeated neck stretching, head jerking,
  or shoulder shrugging. Less commonly, motor tics
  are more "coordinated," with distinct movements
  involving several muscle groups, such as
  repetitive squatting, skipping, or hopping. These
  tics, referred to as complex motor tics, may also
  include repetitive touching of others, deep knee
  bending, jumping, smelling of objects, hand
  gesturing, head shaking, leg kicking, or turning
  in a circle. In addition to affecting the head
  and facial area, motor tics also affect other
  parts of the body, such as the shoulders, torso,
  arms, and legs. The anatomical locations of motor
  tics may change over time. Rarely, motor tics
  evolve to include behaviors that may result in
  self-injury, such as excessive scratching and lip
  biting.

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Vocal tics

• Vocal tics are sudden, involuntary, recurrent,
  often relatively loud vocalizations. Vocal tics
  usually begin as single, simple sounds that may
  eventually progress to involve more complex
  phrases and vocalizations. For example, patients
  may initially develop simple vocal tics,
  including grunting, throat clearing, sighing,
  barking, hissing, sniffing, tongue clicking, or
  snorting. Complex vocal tics may involve
  repeating certain phrases or words out of
  context, one's own words or sounds (palilalia),
  or the last words or phrases spoken by others
  (echolalia). Rarely, there may be involuntary,
  explosive cursing or compulsive utterance of
  obscene words or phrases (coprolalia).

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LIMBIC STRUCTURES

• AMYGDALAHIPPOCAMPUSSEPTUM

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AFFECTIVE IMPUSLES

• The 4-Fs, but different