23-NSCI 2101 -Motor Systems 2024

Somatomotor system

Controls striated skeletal muscles, which is how you move.

Autonomic motor system

Consists of sympathetic and parasympathetic control of heart, blood vessels, and digestive tract.

Upper motor neurons (UMNs)

Start in the cerebral cortex and target lower motor neurons.

Lower motor neurons (LMNs)

Start in the brainstem or spinal cord and directly target muscles.

Neuromuscular junction

The connection between motor neurons and skeletal muscles.

Acetylcholine

Neurotransmitter released from motor neurons to signal muscle contractions.

Skeletal muscles

Muscles that are controlled by motor neurons and are responsible for voluntary movements.

Type I fibers

Muscle fibers that have more mitochondria, are thin, slow, low in force, and slowly fatigued.

Motor unit

A motor neuron and the muscle fibers it innervates.

Corticobulbar tract

Controls head and neck muscles by targeting LMNs in cranial nerve nuclei in the brainstem.

Corticospinal tract

Controls body and limb muscles with lateral and ventral/anterior pathways.

Pyramidal tracts

Motor pathways that descend through the pyramids of the medulla, involved in voluntary movements.

Muscle contraction

Shortening of muscle fibers as myosin slides across actin, requiring ATP.

Botox (botulism toxin)

Blocks acetylcholine release at the neuromuscular junction, causing paralysis.

Upper motor neuron damage

Produces paralysis primarily on the contralateral side of the body.

Rubrospinal tract

A nonpyramidal pathway that coordinates fine limb movements from the red nucleus to the spinal cord.

Amyotrophic lateral sclerosis (ALS)

A motor neuron disease characterized by progressive loss of motor control due to degeneration of UMNs or LMNs.

Vestibulospinal tract

A nonpyramidal pathway that helps maintain balance and head position adjustments.

Reticular formation

Involved in postural control and learned limb movements via the reticulospinal tract.

Muscle fibers

Consist of muscle fascicles, which are bundles of muscle fibers.

Myosin and actin

Motor proteins that interact to cause muscle contraction.

Calcium

Released in response to acetylcholine binding, activating muscle contraction.