Neuroscience of Motor Control: Brain Structures and Reflexes

Muscle spindle

A proprioceptor parallel to the muscle that responds to a stretch.

Golgi tendon organs

Proprioreceptor that responds to increases in muscle tension; "brake" against excessively vigorous contraction

Ballistic movement

Movement that once started has to finish out. Can be subject to feedback correction

Central Pattern Generators

Neural mechanisms in the spinal cord that generate rhythmic patterns of motor output.

motor program

a fixed sequence of movements

Allied reflexes

most movements are combinations of involuntary and voluntary components. Involuntary movements are controlled by subcortical areas, while voluntary movement sequences rely on sensory feedback andare dependent on the cerebral cortex

primary motor cortex

The region in the cerebral cortex that elicits movement, particularly complex ones. It is also active when imagining movements. It does not elicit a fixed movement pattern; rather, the outcome, letting the spinal cord and other areas find the right combination of muscles to get there. Controls activity on the opposite side of the body

Posterior parietal cortex

keeps track of the position of the body relative to the world. it is activated by visual and somatosensory input

supplementary motor cortex

planning and organizing a rapid series of movements

Premotor cortex

active immediately before a movement and organizes the direction of movement in space

Prefrontal cortex

Stores sensory information relevant to movement

mirror neurons

In the inferior frontal and parietal lobes and is active in the preparation of movement and observing others do the movement. It's the basis for identification and empathy.

How do the brain and spinal cord connect

two-way pathways called corticospinal tracts

lateral tract

origninates from the primary motor cortex, surrounding areas, and red nucleus. Controls movement in th eopposite tract

medial tract

axons from the primary and supplementary motor cortex, midbrain, tectum, reticular formation, and vestibular nucleus. Axons do not cross the contralateral side and control bilateral movements in the medial part of the body.

cerebellum

"little brain" with more neurons than the rest of the brain. Balance and coordination are classical functions, but they also process information about guiding movement. Damage can lead to deficiencies in ballistic movements and precise judgment of short time intervals. DOES NOT impair continuous motor activity (drawing circles)

basal ganglia

a set of subcortical structures that directs intentional movements. consists of the caudate nucleus, putamen, and globus pallidus. The role is to regulate the vigor of the movement.

Parkinsons symptoms

Muscle tremors, rigidity, stiffness, slowed-down movements, and problems with balance

Also slow in cognitive tasks, difficulty initiating mental and physical activity. Risk factors: begin when the substania nigra neurons decrease. treat with L-DOPA