Motor Control Concepts & Motor Cortex

Vocabulary flashcards for motor control concepts and motor cortex based on lecture notes.

Primary Motor Cortex

Executes commands to motor neurons; stimulation elicits simple movements of single joints.

Primary Motor Cortex Location

Located in the precentral gyrus (frontal lobe); houses cell bodies of the upper motor neurons.

Premotor Cortex

Receives input from sensory areas; significant role in planning movement; integrates sensory information; spatial guidance of movement.

Supplementary Motor Cortex

Sequences movement; feeds motor instructions in the correct sequence to the primary motor cortex; active during mental rehearsal of coordinated movements.

Reflexes

Involuntary, rapid, and stereotyped movements initiated by an external stimulus.

Rhythmic Motor Patterns

Combines voluntary and reflexive acts; initiation and termination voluntary, but the movement is repetitive and reflexive once initiated.

Voluntary Movements

Complex, purposeful, and goal-oriented actions that are learnt and can be improved with practice; initiated at the cerebral cortex level.

Motor Control

The ability to regulate or direct the mechanisms essential to movement.

Central Pattern Generators

Neuronal circuits that produce rhythmic motor patterns in the absence of sensory or descending inputs that carry specific timing information.

Stepping Pattern Generator

Adaptable network of spinal interneurons that activate the lower motor neurons which innervate muscles.

Proprioception

Awareness of self in space; comes from receptors in the PNS (muscle spindles, Golgi tendon organs, joint & touch/pressure receptors).

Visual System in Motor Control

Provides information about visual cues & guidance during movement.

Vestibular System

CNVIII; Input from inner ear receptors; important role in head positioning relative to gravity during movement.

Hierarchical Model of Motor Control

Organisational control that is from the top down with a high emphasis on cortical areas; higher centres inhibit lower reflex centres.

Dynamical Systems Theory

Views the whole body as a mechanical system with mass that is subjected to external & internal forces.

Ecological Approach to Motor Control

Suggests motor control evolved to cope with the environment; actions require perceptual information specific to a desired goal-directed action within a specific environment.

Upper Motor Neurons Location

Upper motor neuron cell bodies are found either in the primary motor cortex or the brainstem.

Corticospinal Tract

Descending upper motor neuron tract: from the cortex → spinal cord for motor pathways.

Corticobrainstem/Corticobulbar Tract

Pathway innervates cranial nerves that have a motor output.

Reticulospinal Tract

Arises from the reticular formation; helps with awareness, reflexive head movement responding to visual or auditory input, and muscle tone.

Vestibulospinal Tract

Arises from the vestibular nucleus in the brainstem to help control neck & upper back muscles; aids in balance and head positioning.

Rubrospinal Tract

Arises from the red nucleus in the midbrain but has minimal contribution to upper limb extensor muscles.

Lower Motor Neurons

Transmit signals to skeletal muscles, eliciting the contraction of muscle fibres; the only neurons that convey signals to skeletal muscle fibres.

Alpha Lower Motor Neurons

Large cell bodies & myelinated axons that project to extrafusal muscle fibres.

Gamma Lower Motor Neurons

Medium sized myelinated axons that projects to intrafusal muscles in the muscle spindles and regulates stretch.

Motor Unit

One alpha lower motor neuron & all the muscle fibres it innervates.

Lesions

Tissues that show damage from injury or disease to the CNS/PNS.

Hypertonia

Increase in muscle tone; impaired UMN will lead to the LMN continually activating the muscle.

Spasticity

Resistance to passive movement varies depending on the velocity of movement.

Hyperreflexia

Loss of inhibitory corticospinal input & enhanced excitability of LMN & interneurons results in excessive LMN response to afferent input.

Muscle Atrophy

Wastage with disuse.

Decerebate Rigidity

Rigid extension of the limbs & trunk, internal rotation of the upper limb & plantarflexion caused by severe midbrain lesions.

Decorticate Rigidity

Rigid flexed upper limbs, extended neck + lower limbs & plantarflexion caused by severe lesions above the midbrain.

Hypotonia

Decrease in muscle tone.

Hyporeflexia

Below normal amount of reflexes.

Reflex

An involuntary motor response to an external stimulus.

Phasic Stretch Reflex

Muscle contraction in response to a quick stretch.

Cutaneous Reflex

Afferent information from the skin, muscles & joints can elicit a variety of withdraw movements modulated in the spinal cord.

Gag Reflex

Protective mechanism to prevent unwanted entry of a foreign body to the respiratory passage which could lead to choking.

Babinski’s Sign

The extension of the great toe, often accompanied by fanning of the other toes; indicates demyelination of the corticospinal tract in adults.

Areflexia

Absence of reflexes due to damage to the lower motor neuron & sensory pathway.