Final answer:
Motor development follows an ordered sequence and is influenced by cultural context. It involves an intricate connection between various parts of the brain and the skeletal muscles, primarily controlled by the corticospinal and corticobulbar tracts.
Step-by-step explanation:
The two main principles that motor development follows are the orderly sequence of motor skill acquisition and the influence of cultural context on motor development. Motor development occurs in an orderly and predictable sequence; infants first learn to control their head movements, then sit with assistance, progress to sitting unassisted, and eventually develop the skills to crawl and walk. However, these stages can be influenced by cultural practices, meaning that the context can either accelerate or inhibit the achievement of these milestones. Moreover, the development of motor skills, like any cortical motor functions, rely heavily on the efficient functioning of the skeletomotor system, particularly the two-cell projection from the precentral gyrus of the frontal lobe to the skeletal muscles, and involves both upper motor neurons and lower motor neurons for voluntary movement.
Motor tests assess muscle tone and strength and involve input from upper and lower motor neurons. The adjacent areas to the primary motor cortex, such as the premotor cortex and the supplemental motor area, assist in planning and coordinating movements. And finally, the descending pathways, mainly the corticobulbar and corticospinal tracts, are responsible for voluntary skeletal muscle movements.