Motor System and Prefrontal Cortex

• The motor system is a complex network involving various brain regions and the spinal cord, orchestrating both voluntary and involuntary movements through intricate pathways.

The Prefrontal Cortex and Executive Function

• The prefrontal cortex plays a role in personality.
• Phineas Gage's case involved damage to the prefrontal cortex and showed it plays a critical role in personality.
• Phineas Gage experienced personality changes after an accident involving a metal spike impaling his prefrontal cortex in 1848.
• After his accident, Gage became more irritable and lazy, illustrating the prefrontal cortex's role.
• Gage's eventual adaptation as a stagecoach driver highlights the brain's recovery potential.

Primary and Secondary Motor Cortices

• The primary motor cortex is in the precentral gyrus of the frontal lobe.
• The primary motor cortex produces skeletal muscle contractions by stimulating spinal cord neurons, containing a "motor homunculus" map that illustrates brain control of different body parts.
• Motor commands descend through the corticobulbar and corticospinal tracts, targeting either the brainstem or spinal cord thus controlling voluntary skeletal muscle movements.
• Secondary motor cortices include the premotor cortex, supplemental motor area, frontal eye fields, and Broca’s area.
• The premotor cortex is located laterally and controls core muscle movements for posture.
• The supplemental motor area is located medially and superiorly and coordinates planned, sequential movements based on past experiences.
• Frontal eye fields manage eye movements in response to visual stimuli.
• Broca’s area handles speech production.

Corticospinal Tract

• Axons from the cortex travel through the internal capsule and cerebral peduncles to reach the brainstem and spinal cord.
• Most axons cross over at the medulla, forming the lateral and anterior corticospinal tracts in a process called pyramidal decussation.
• The lateral corticospinal tract controls arm and leg muscles, with larger ventral horns in the cervical and lumbar spinal cord allowing nuanced motor control.
• The anterior corticospinal tract controls trunk muscles through bilateral coordination, essential for posture and broad body movements.

Extrapyramidal System

• The tectospinal tract originates in the midbrain and manages postural movements via the superior colliculus.
• The reticulospinal tract connects the reticular system to the spinal cord, influencing posture, locomotion, muscle tone, and autonomic functions.
• The vestibulospinal tract involves brainstem vestibular nuclei, modulating balance and movement based on equilibrium information.
• Subcortical influences, including secondary motor cortices and basal nuclei, modulate movements initiated by the CNS, providing feedback and coordination through various pathways.
• The cerebellum compares cerebral motor commands with proprioceptive feedback, ensuring movements are executed smoothly.

Conclusion

• The motor system's complexity involves numerous brain and spinal structures to execute precise, coordinated movements.
• Historical cases and studies reveal intricacies and resilience, enhancing understanding of function and potential therapeutic interventions.
• Motor control research continues to evolve, offering insights into normal function and potential therapeutic interventions for motor impairments.