Course Lectures of Dr Shahriar GharibzadehBy: Mohammad Ali Ahmadi Pajouh
April 2008
SubjectsThree Types of Movements:
ReflexesRhythmic Motor PatternsVoluntary
Two Basic Modes of Muscular Control:Phasic ControlTonic Control
Three levels of Motor Control Circuits:Spinal CordBrain StemForebrain
Reflexive and Rhythmic MovementsAre Produced by Stereotyped Patterns of
Muscle ContractionReceptors in muscles produce stretch
reflexesCutaneous receptors produce withdrawal
reflexeslocal sign: In reflexes the particular muscles
that contract in response to a stimulus vary with the site of stimulation.
If external conditions remain the same, a given stimulus will elicit the same response time after time.
However, both the intensity of the response and the local sign of reflexes can be modulated by mechanisms that switch the patterns of connections of afferent fibers to spinal interneurons and motor neurons depending on the context of the behavior.
Repetitive rhythmic motor patternschewing, swallowing, and scratching, as well
as the alternating contractions of flexors and extensors on either side of the body during quadrupedal locomotion.
The circuits for these repetitive rhythmic motor patterns lie in the spinal cord and brain stem. Although these patterns may occur spontaneously, they are more commonly triggered by peripheral stimuli that activate the underlying circuits.
Voluntary MovementsVoluntary Movements Are :
Goal-Directed and
Improve With Practice
as a Result of Feedback and
Feed-Forward Mechanisms
Three LawsThe brain represents the outcome of motor
actions independently of the specific effector used or the specific way the action is achieved.
The time taken to respond to a stimulus depends on the amount of information that needs to be processed to accomplish the task.
There is a trade-off between the speed of a movement and its accuracy.
Motor Equivalence
Movement Kinematics and Dynamics
The motor program specifies the spatial features of the movement and the angles through which the joints will move.
The program must also specify the forces required to rotate the joints (torques) to produce the desired movement.
Motor Program
Lifting a slippery object
Movement PrimitivesThe simple spatiotemporal elements of a
movement.
Feedback Control
Feed-forward Control
feed-forward and feedback controls
The Motor Systems Are Organized Hierarchicaly
Spinal CordBrain StemForebrain
+Cerebellum Basal Ganglia
Cerebral Cortex
SummeryThree Types of Movements:
ReflexesRhythmic Motor PatternsVoluntary
Three levels of Motor Control Circuits:Spinal CordBrain StemForebrain
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