Goal-Directed Behavior and Reflexive Behavior

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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.
http//www.youtube.com/watch?vp_uhP1vDfoo
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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.
• http//www.youtube.com/watch?vgewP1T7GYcc

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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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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 motor unit helps us understand resolution
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The motor unit If ratio is highlow resolution
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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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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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Disease of the NMJ? MG
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MG
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MG
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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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the final common path