Primary Motor Area
The primary motor cortex is a brain region that in humans is located in the posterior portion of the frontal lobe. It works in association with other motor areas including premotor cortex, the supplementary motor area, posterior parietal cortex, and several subcortical brain regions, to plan and execute movements. Primary motor cortex is defined anatomically as the region of cortex that contains large neurons known as Betz cells. Betz cells, along with other cortical neurons, send long axons down the spinal cord to synapse onto the interneuron circuitry of the spinal cord and also directly onto the alpha motor neurons in the spinal cord which connect to the muscles. The primary motor cortex contains a rough map of the body, with different body parts controlled by partially overlapping regions of cortex arranged from the toe (at the top of the cerebral hemisphere) to mouth (at the bottom) along a fold in the cortex called the central sulcus. Each cerebral hemisphere contains a map that controls mainly the opposite side of the body.
For the discovery of the primary motor cortex and its relationship to other motor cortical areas, see the main article on the motor cortex.
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