Neural Concepts in Movement

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Neural Concepts in Movement
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Generating an Action Potential (AP)

• Plasma Membranes
• Membrane
• Fluids
• Ion Concentrations
• Concentration Gradient
• Electrical Force

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Generating an Action Potential (AP)

• Resting membrane Potential
• Electrical Potential
• --60 mV to -- 70-90 mV
• Membrane Potential
• Na/K pump
• 3 NA out
• 2 K in
• Negatively charged inside

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Generating an Action Potential (AP)

• Depolarization
• Changes within membrane
• Chemically, electrically, mechanically
• Ion Channels Open
• Na
• K
• Change is transient

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Generating an Action Potential (AP)

• Repolarization
• NA channels close
• K channels open
• Hyperpolarization
• Membrane more negative than at rest
• Lasts 50 ms
• Na/K pumps

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Generating an Action Potential (AP)

• Refractory Period
• amount of time it takes for an excitable membrane
  to be stimulated and then be ready for stimulus
  again
• Membrane more polarized than at rest

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Summary Generating an Action Potential (AP)

• Action Potential
• http//www.youtube.com/watch?vSCasruJT-DU

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Propagation of the AP

• Domino effect
• Na influx
• Stimulates next Na channels to open
• http//www.youtube.com/watch?vJaj4Nle1y20feature
  PlayListp57B1812113CB9281playnext1index50

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Neuromuscular Junction

• Electrical to Chemical to Electrical
• Neurotransmitters
• Acetylcholine

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Process of Developing a Muscle Contraction

• Twitch
• Mechanical response of a muscle fiber to a single
  AP

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Process of Developing a Muscle Contraction

• Summation
• A 2nd AP is initiated during the first mechanical
  activity
• Increases mechanical response
• Increasing frequency of APs

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Process of Developing a Muscle Contraction

• Tetanus
• Unfused Tetanus
• Fused Tetanus

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Innervation of Skeletal Muscle

• Extrafusal Muscle Fiber
• Alpha Motorneurons
• Intrafusal Muscle Fiber
• Gamma Motorneurons

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Motor Unit

• An individual motor neuron, together with all its
  axons and all muscle fibers associated with these
  axons
• Innervation ratio
• All-or-none Principle

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Locations of Motor Units

• Specific Region
• Different Parts of Muscle

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Motor Unit Recruitment

• MU Types
• Size Principle
• Number Available
• Number Active
• Rate at which recruited
• Factors Determining Tension

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Sensory Components of Movement

• Sensory Receptors (Mechanorecpetors)
• Cutaneous
• Deep pressure and touch
• Certain locations joint position and movement
  awareness

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Sensory Components of Movement

• Sensory Receptors (Mechanorecpetors)
• Joint Receptors
• Joint capsule and ligaments
• Joint position and rate of movement
• Only at extreme ranges of motion

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Sensory Components of Movement

• Sensory Receptors (Mechanorecpetors)
• Muscle Receptors
• Golgi Tendon Organs
• Muscle Spindles

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Sensory Components of Movement

• Muscle Sensory Receptors
• Golgi Tendon Organs
• Lie within musculotendinous junction
• Stimulated by muscle tension
• Function

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Sensory Components of Movement

• Muscle Sensory Receptors
• Muscle Spindles
• Lie parallel and within the muscle fibers
• Anatomy of a muscle spindle
• What happens when stimulated
• Function

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Sensory Components of Movement

• Vision
• Horizontal and vertical cue
• Orientation to environment
• Vestibular
• Inner ear
• Head movement and position

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Reflexes

• Stretch Reflex
• Physiology
• Function

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Reflexes

• Reciprocal Inhibition
• Physiology
• Function

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Reflexes

• Autogenic Inhibitions
• Physiology
• Function

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Reflexes

• Withdrawal
• Physiology
• Function

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Reflexes

• Crossed Extensor
• Physiology
• Function

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How does the NS control multi-joint segments?

• Central Pattern Generators
• Location
• Automatic movements
• Specific to action controls
• Location
• Initiated by command neurons

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Supraspinal Control of Movement

• Spinal Cord
• Brain Stem
• Functions
• Efferent fibers go to SC to influence motor
  neurons

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Supraspinal Control of Movement

• Cerebral Cortex
• Major integrating center
• Somatropic map
• Movements based on perceived need
• Roles of Motor Areas
• Preparation of movement
• Anticipation of movement
• Signal-related activity
• Visual Guidance
• Conditional Response
• Sequential Movements

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Supraspinal Control of Movement

• Cerebellum
• No direct efferent to SC and brain stem
• Functions
• Timing Device
• Learning Device
• Coordinator

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Supraspinal Control of Movement

• Basal Ganglia
• Functions
• Motor planning of direction. Amplitude velocity
• Movement initiation
• Postural role
• Adapting motor output to changing conditions

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Movement Strategies

• Feedforward
• Efferent response in absence of feedback
• Requirements
• How does it work?

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Movement Strategies

• Feedback
• Sensory information alters feedforward
• Provide CNS with outcome
• Time dependent

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Putting it Together

• Most movement combinations of feedforward and
  feedback
• Feedforward sets the activation pattern
• Feedback informs system if desired outcome
  occurred
• Unanticipated event?