Brain Control of Movement (Chapters $$17$$, $$18$$, and $$19$$)

This set of vocabulary flashcards covers the hierarchical organization of motor systems including the motor cortex, brainstem pathways, basal ganglia circuits, and cerebellar functions described in Chapters $$17$$, $$18$$, and $$19$$.

Upper Motor Neurons

Direct control neurons located within the brain responsible for organizing most voluntary movement and descending through the spinal cord in two major systems.

Lateral Pathways

Descending pathways originating primarily from the cerebral cortex responsible for skilled voluntary motion and precise movements of the hands and fingers.

Ventromedial Pathways

Descending systems arising primarily from brainstem motor centers that regulate posture, balance, and locomotion using axial and proximal muscles.

Primary Motor Cortex

Located in the precentral gyrus (Broadman Area $4$), this region is somatotopically organized and participates in the execution of complex voluntary actions.

Motor Homunculus

A motor map within the primary motor cortex where the amount of cortical territory devoted to a body region reflects the degree of motor control required.

Premotor Cortex

A region rostral to the primary motor cortex involved in movement planning and preparation, receiving input related to sensory events and behavioral goals.

Vet cells

The largest neurons of the central nervous system, which are pyramidal neurons located in layer $5$ of the cerebral cortex.

Mirror Neurons

Specialized neurons within the lateral premotor cortex that become active when an individual performs an action or observes that same action in another.

Supplementary Motor Area

Also known as the medial premotor cortex, this area is involved in movements guided by internal cues and generating movements from memory.

Posterior Parietal Cortex

A region that integrates sensory information and transforms it into movement-related representations for motor planning.

Pyramidal Decussation

The crossing of the majority of corticospinal fibers at the caudal medulla, resulting in the right motor cortex primarily controlling the left side of the body.

Vestibulospinal Tract

A brainstem motor pathway that uses information from the vestibular apparatus to help maintain upright posture and stability during balance disturbances.

Reticular Formation

A network of interconnected nuclei throughout the brainstem involved in cardiovascular regulation, sleep-wake cycles, and motor control via reticulospinal pathways.

Reticulospinal Pathways

Pathways that help regulate posture and coordinate locomotion; the pontine formation generally facilitates extensor activity while the medullary formation can reduce extensor tone.

Striatum

The primary entry point for motor information to the basal ganglia, consisting of the caudate nucleus and the putamen.

Medium Spiny Neurons

A population of neurons within the striatum that serve as principal integrators of information entering the basal ganglia from the cortex, thalamus, and brainstem.

Disinhibition

A mechanism of the basal ganglia where the activity of striatal neurons inhibits the inhibitory neurons of the globus pallidus, thereby releasing the thalamus from suppression.

Direct Pathway

A basal ganglia circuit that facilitates movement initiation by reducing thalamic suppression through the inhibition of the internal segment of the glottis pallidus ($GPI$).

Indirect Pathway

A complex basal ganglia circuit that suppresses competing motor activity by increasing the inhibitory output of the thalamus via the subthalamic nucleus ($STN$).

Center Surround Model

A model where the direct pathway acts as a center mechanism to reduce inhibition for intended movement while the indirect pathway acts as a surround mechanism to suppress competing actions.

Huntington's Disease

A neurodegenerative disease caused by the degeneration of medium spiny neurons in the striatum, leading to a failure to effectively suppress competing motor programs and producing involuntary movements.

Parkinson's Disease

A disorder resulting from the degeneration of dopaminergic neurons in the substantia nigra, shifting the basal ganglia balance toward excessive inhibition of thalamic motor circuits.

Cerebrocerebellum

The lateral functional region of the cerebellum involved in the planning, timing, and execution of complex, precisely sequenced voluntary motion.

Spinocerebellum

A cerebellar region including the vermis and intermediate zones that receives input from the spinal cord to monitor body position and ongoing motion.

Vestibulocerebellum

Functional division of the cerebellum consisting of the flocculo nodal lobe that contributes to balance, posture, and vestibulo-ocular reflexes.

Deep Cerebellar Nuclei

Nuclei located beneath the cerebral cortex, including the dentate, interposed, and vestigial nuclei, which provide the final outputs of the cerebellum.

Purkinje Cells

The sole output neurons of the cerebellar cortex that provide inhibitory projections to the deep cerebellar nuclei.

Mossy Fibers

Excitatory cerebellar input fibers from the cerebral cortex, brainstem, and spinal cord that synapse onto granule cells within the cerebellar cortex.

Climbing Fibers

Powerful input fibers originating from the inferior olive that convey signals related to movement error and motor learning to Purkinje cells.