Motor Control Practice Flashcards

Flashcards covering the neural structures, pathways, and clinical syndromes associated with motor control as presented in Chapter 16.

What is the definition of motor systems?

Neural structures that control the contraction of somatic muscles.

Where do the descending projection pathways of the motor system originate?

Cerebral cortex and brainstem.

Which two structures modulate the activity of the descending projection pathways?

The basal nuclei and cerebellum.

Where are the cell bodies of 1st-order (upper motor) neurons located?

In the cerebral cortex or brainstem centers.

What structures are formed by the axons of 1st-order motor neurons?

Descending tracts.

What is the classification of 2nd-order motor neurons?

Local circuit neurons or interneurons in the brainstem or ventral horn.

Where are the cell bodies of 3rd-order (lower motor) neurons located?

In the ventral horn of the spinal cord or cranial nerve nuclei of the brainstem.

Where do the axons of 3rd-order motor neurons synapse?

Skeletal muscle fibers.

Which brain region translates goals into action sequences?

Prefrontal cortex.

What is the function of the premotor cortex during movement learning?

It organizes movements during learning using sensory feedback.

How does the supplementary motor area organize previously learned movements?

By using an internal model.

What is the primary role of the basal ganglia in motor control?

Initiating and modifying action sequences.

Which structure implements the feed forward model of motor outcomes?

Neocerebellum.

What are the major systems identified as 1st-order upper motor neurons?

Primary and premotor cortices, brain stem motor nuclei, cerebellum, and basal nuclei.

What defines the neocortex of the primary motor cortex?

A thick layer 5.

What is the specific function of Betz cells in the primary motor cortex?

They activate lower motor neurons (LMN) that control distal limbs.

Where do pyramidal cells of the primary motor cortex terminate?

On interneurons of the brainstem or spinal cord.

Where does the corticobulbar tract terminate?

In the brainstem.

What does the corticobulbar tract innervate for voluntary movement?

Cranial nerve (CN) motor nuclei and cranial muscles.

Which lateral brainstem structures are targets of the corticobulbar tract?

Red nucleus, reticular formation, and pons (corticopontine tract).

Where does the lateral corticospinal tract decussate?

In the caudal medulla.

Which muscles are controlled by the lateral corticospinal tract?

Distal limb muscles for coordinated hand and finger movements.

Where does the ventral corticospinal tract travel and does it decussate?

It travels in the pyramid and does not decussate.

Which muscles are innervated by the ventral corticospinal tract?

Axial and proximal limb muscles.

What is the primary function of the primary motor cortex?

Execution of motor skills and controlling movements rather than individual muscles.

What are the three major regions of the premotor cortical regions?

Lateral premotor areas, supplementary motor areas, and cingulate motor areas.

Which regions provide input to the premotor cortical areas?

Parietal lobules and prefrontal cortex.

What are the primary functions of lateral premotor areas?

Movement intentions (selection based on external events) and mirroring intentional movements of others.

Which specific area for speech articulation is part of the lateral premotor areas?

Broca’s area.

What is the result of damage to the lateral premotor areas?

Loss of ability to choose movement in response to visual cues or verbal commands.

Where is the supplementary motor area located?

Medial surface of the premotor cortex.

From which thalamic nucleus does the supplementary motor area receive input?

Ventral anterior nucleus of the thalamus (from the basal ganglia).

What functions are associated with the supplementary motor area?

Self-initiated or spontaneous movements, direction of gaze (frontal eye field), and bimanual coordination.

Which Brodmann’s areas correspond to the cingulate motor area?

Areas 6, 23, and 24.

What is the specialized function of the cingulate motor area?

Emotional and motivational regulation of movement.

How do long-distance (propriospinal) interneurons coordinate movements?

By connecting many segments, both ipsilaterally and contralaterally, for posture and limb coordination.

What is the function of short-distance (segmental) interneurons?

Fine control of distal muscles of extremities.

What neurotransmitter is used by 3rd-order lower motor neurons?

 Acetylcholine.

What is the role of Alpha ($\alpha$) motor neurons?

Force generation in extrafusal fibers.

What is the role of Gamma ($\gamma$) motor neurons?

Sensory function related to the length of muscle in intrafusal fibers.

What is a motor neuron pool?

All of the motor neurons innervating a single muscle grouped together.

Describe the medial-to-lateral topography of motor neurons in the ventral horn.

Medial corresponds to axial muscles and lateral corresponds to distal limb muscles.

What are Central Pattern Generators (CPGs)?

Interneuron circuits that synchronize complex movements (rhythmic or oscillatory) and control timing/coordination.

Where is the breathing CPG located?

Cervical spinal cord.

What are the classic symptoms of lower motor neuron syndrome?

Paralysis or paresis, areflexia, loss of muscle tone, atrophy, fasciculations, and fibrillations.

How does the transcript define fasciculations?

Spontaneous twitches due to loss of single muscle fiber innervation.

How does the transcript define fibrillations?

Spontaneous twitches due to loss of motor unit.

What occurs during Amyotrophic lateral sclerosis (ALS)?

Slow degeneration of $\alpha$ motor neurons in the spinal cord and brain stem (LMNs) and the motor cortex (UMNs).

According to the transcript, what is the prevalence and prognosis of ALS?

It affects $0.05\%$ of the population and typically results in death within $5\,\text{years}$ of onset.

Contrast the reflex signs of upper versus lower motor neuron syndrome.

Upper motor neuron syndrome causes hyperactive deep reflexes, Babinski’s sign, and clonus, while lower motor neuron syndrome causes hypoactive superficial and deep reflexes (areflexia).