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Control of Movement
- accomplished by the hierarchical organization of the nervous system
- and by constant integration of sensory information with motor control
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Motor Control
- The lowest level of motor control is performed by alpha motor neurons(lower motor neurons)
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located in the spinal cord and the brain stem (midbrain, pons and medulla) - -Alpha motor neurons are partly under the control of sensory input, which can lead to the generation of reflexes
- -The output of alpha motor neurons can be organized by pattern generation mechanisms, which organize rhythmic activities such as winged flight, locomotion, or chewing
- -alpha motor neurons
- are under the control of upper motor neurons, which originate in motor
- areas of the frontal lobe in the neocortex
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a person paralyzed by damage to either lower motor neurons or upper motor neurons, though the symptoms of the paralysis are different in each case
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Motor Related Areas in the Neocortex
- All in the frontal lobe
- primary motor cortex - located near the central sulcus.
- - Many upper motor neurons have their cell bodies in the primary motor cortex
- - this region is somatotopically organized (i.e., organized according to body parts)
- - brain damage that is restricted to primary motor cortex are not necessarily paralyzed, but do show motor weakness and lose ability to exert independent control over fingers. (person could move his fingers together, as if he or she was wearing a mitten, but this person could not play the piano or type with individual finger movements)
- premotor cortex, the supplementary motor cortex, and the prefrontal cortex- there is a motor map of the body in primary motor cortex and multiple representations of the body in these various motor areas of the frontal lobe
- - Upper motor neuron cell bodies are not restricted to the primary motor cortex, but are located in several areas distributed over the motor regions of frontal lobe
- - the axons from these upper motor neurons exit from the neocortex and descend to other motor areas and form bundles of tracts that are very close together
- - person who has a stroke that damages virtually all the fibers that control a body part can show upper motor neuron paralysis in that body part
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Neocortex
- - Exerts a profound influence over motor output in all mammals, particularly in primates such as humans
- - however the neocortex could not perform its motor control functions properly if it were not interconnected with other motor control areas
- - cerebellum is very important for motor control, including aspects of locomotion, coordination, and motor skill learning and sensory/motor integration
- - The basal ganglia are important for facilitating speed and coordination of movement, for responding to sensory input, and also for aspects of motor learning
- - Depletion of the neurotransmitter dopamine from the caudate/putamen results in the motor disorder known as Parkinson’s disease.
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