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

Thanks