Final answer:
The primary motor cortex is located in the precentral gyrus of the frontal lobe and is pivotal for controlling voluntary movements by sending commands to the spinal cord to contract skeletal muscles. It has a detailed body map for motor functions and works in conjunction with secondary motor cortices that plan these movements.
Step-by-step explanation:
Function of the Primary Motor Cortex
The primary motor cortex is a key region in the precentral gyrus of the frontal lobe responsible for controlling voluntary muscle movements.
A neurosurgeon named Walter Penfield contributed significantly to our understanding of this cortex by electrically stimulating it during surgery, which allowed for the mapping of its functions.
The motor cortex harbors a motor homunculus, which is a topographical representation of the body; this map shows that areas requiring precise and agile control, like fingers and facial muscles, occupy more cortical space than those for coarser movements, such as the muscles in the buttocks and back.
Furthermore, it receives input for planning movements and its principal output sends commands to the spinal cord which trigger the contraction of skeletal muscles, hence executing voluntary movements.
Supporting the primary motor cortex are the secondary motor cortices, which include the premotor cortex and the supplemental motor area.
These areas prepare and plan the movements before the primary motor cortex sends the final signal to elicit movement.
Also adjacent are areas like the frontal eye fields for eye movements and Broca's area for speech production. In all, the primary motor cortex plays a central role in carrying out movement after it is planned by the secondary motor regions.