motor function

Meaning: Motor function is the nervous system's control of movement. Voluntary movement is planned in the premotor cortex and supplementary motor area, then commanded by the primary motor cortex in the frontal lobe's precentral gyrus. Signals pass down the spinal cord to motor neurons that activate skeletal muscle. The basal ganglia help initiate and smooth movement, and the cerebellum coordinates timing, balance and motor learning. Simple reflexes can be handled at the spinal cord without the brain.

On the MCAT: A passage may show the motor homunculus, a map of the body across the motor cortex. Hands, lips and tongue get large areas because they need fine control. Lesion questions ask for the deficit: damage to the primary motor cortex weakens movement mainly on the opposite side of the body; cerebellar damage gives clumsy, poorly coordinated movement and poor balance; basal ganglia damage disrupts starting and smoothing movement.

Common confusion: The motor cortex (precentral gyrus, output to muscles) is not the somatosensory cortex (postcentral gyrus of the parietal lobe, which receives touch input). Also, the area a body part gets on the homunculus tracks the precision of control it needs, not the physical size of that body part.