فصل سوم- فرضيه ها و استراتژيهاي حركات 3-1 Centeralism 3-2 Prepheralism 3-3 Motor Program 3-4 Equilibim Hypothesis 3-5 Impedance Control فصل چهارم- حركتهاي متناوب و راه رفتن 4-1 ويژه گيهاي راه رفتن 4-2 Cenral Pattern Generator فصل پنجم- ياد گيري حركت و مدلهاي ارائه شده براي حركت - PowerPoint PPT Presentation
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Some reflexes short pathways in spinal cord linking dorsal & ventral roots, others longer loops (spinal cord interconnections or to the brain)
Reflexes as basic units of movement (Sherrington, early 20th century)
BUT: Speech as ordered stimulus-response units problematicSo...
MOTOR PLANS/PROGRAMS
complex movements & acts produced and controlled by set of commands to muscles, established before onset. Feedback on execution
THE CONTROL SYSTEMS VIEW
Machine design vocabulary: accuracy and speed criteria
Closed-loop and Open-loop ctrl mechanisms to optimize performance
CLOSED-LOOP CTRL MECHANISMS
continuous feedback from controlled system to controller (e.g. driving) slow, sustained movements (ramp/smooth) accuracy & flexibility at speed expense
OPEN-LOOP CTRL MECHANISMS
activity preprogrammed sensor measured output(no external form of feedback rapid responses -ballistic movements (e.g. throwing a fastball) no feedback/ error reduction: anticipation (prior learning)
1 skeletal system & muscles: movements possible2 spinal cord:
a)ctrl skeletal muscles in response to sensory info (reflexes)
b) implementation of motor commands3 brainstem:
integration & relay of motor and sensory info from brain & spinal cord and in reverse, respectively4 primary motor cortex (M1):
motor commands initiation
THE NEUROBIOLOGICAL VIEW ctnd
5 premotor cortex: programs levels of motor cortical processing
6 basal ganglia & cerebellum: modulate activities of hierarchically
organized motor ctrl systems
Limbic System
Associative Cortex
Cerebellum Motor Cortex Basal Ganglia
Spinal Cord
Musculo-Skeletal System
Movement
Motor Program
Need
Plan
Highest Level
Lowest Level
MiddleLevel
VOLUNTARY MOVEMENTS vs REFLEXES
VOLUNTARY purposeful tasks open to experience/learningInternally generated (potentially) dissociated stimulus aspects : informational content-capacity to trigger movement (in higher motor system’s levels)
REFLEXES stereotyped stimulus-response relationshipenvironmentally triggeredstimulus aspects linkedorganized in spinal & brain stem circuits in response to somatosensory, vestibular stimuli
MUSCULAR CTRL OF ACTION OF SKELETAL SYSTEM muscles generate force by contraction springlike properties influence timing & forces generatedConnected to bones by tendons/ attachment indicative of mediated movement reciprocal arrangements around joints (flexion/extension) (e.g. arm biceps/triceps)- antagonists & synergists (act together) coordinated action around joint might require set of motoneurons excited the antagonistic set inhibitedLimb locked in position by contraction of opposed muscles body posture maintenance, movement around joint, other muscles not act on skeleton (abdomen contraction)
MUSCLE TYPES smooth (stomach): contractions regulated by autonomic system Skeletal: under voluntary control
[Muscle fibers overlapping filaments(made of actin & myosin) give the striped appearanceM.fibers : single large cells with many nuclei (thousands compose a muscle)Contraction increases overlap(myosin binds to actin, filaments slide past one another)-length shortens]
MUSCLE FIBERS TYPES
1) fast : for quick, accurate not maintained movement (e.g. extraocular muscles composed of those)2) slow : resiliency to fatigue (posture maintenance)