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Theme 5. HIERARCHY AND ORGANIZATION OF CONTROL SYSTEMS OF MOVEMENT (iv.…
Theme 5. HIERARCHY AND ORGANIZATION OF CONTROL SYSTEMS OF MOVEMENT
i. Upper neuron control of the brainstem and the spinal cord,
Lateral and medial descending motor neural pathways.
UMNs bodies are found in the cerebral
cortex and in the brainstem
They exert supranuclear control of the
LMNs of the cranial and spinal nerves.
UMNs are responsable for conveying
impulses for voluntary motor activity.
UMNs synapse indirectly by interneurons
rather tan directly on LMNs of the spinal cord
Upper motor neurons Actions
2.- Inhibition
3.- Gating of reflexes
Excitation
Direct Pathways
Corticobulbar tract
Head/face/neck.
Anterior corticospinal tract
Axial and limb proximal muscles
Anterior LMNs spinal cord.
Lateral corticospinal tract
Fine movements of extremities/fingers
Anterior LMNs spinal cord
ii. Motor control hierarchy.
Somatic Motor System
3 Classes of movement
Rhythmic, repetititve motions
Reflex response
Voluntary movement
Motor Control System
Cerebral cortex motor areas
Brainsteam
Spinal cord
PRECOMAND
LEVEL
Basal ganglia
Cerebellum
SEGMENTAL LEVEL
Spinal cord
PROJECTION LEVEL
Motor cortex
Brainstem
iii. The primary motor and premotor cortex. Planning,
programming and execution of motor functions.
SMC is responsable for planning of complex
movements of the contralateral extremities.
The primary motor cortex directly control spinal motor neurons through the pyramidal tracts for precise movement
MPC projects directly to the spinal cord to control trunk and proximal limbs necessary for posture and coordination
iv. Descending cortical tracts in red in the image.
Rubrospinal tract
Medullary (lateral) reticulospinal tract
Lateral costicospinal (pyramidal) tract
Pontoresticulospinal (medial reticulospinal) tract
Interfascicular (semilunar) fasciculus
Vestibulospinal tract
Anterior (ventral) costicospinal tract
Tecstospinal tract
Lateral corticospinal (pyramidal) tract
v. The upper motor neuron syndrome.
Damage to the descending motor pathways anywhere
Chronic hypertonia
Rigidity/spasticity.
Other symptoms:
Hyperactive clonus
Hyporeflexia
Loss of the ability to performfine movements
Acute hypotonia
Spinal shock.
