Primary Motor Cortex

Keta Bhakta, Sharon Linde
  • Author
    Keta Bhakta

    Keta Bhakta graduated from University of Minnesota with a B.S. in Neuroscience and then with a D.D.S. as a dentist. She has tutored many students in various math and science subjects. She began working as a professor at the University of Minnesota School of Dentistry in 2013.

  • Instructor
    Sharon Linde

    Sharon has an Masters of Science in Mathematics and a Masters in Education

What is the motor cortex? Learn the definition, function, and location of the primary motor cortex area of the brain. Learn about the supplementary motor area. Updated: 09/07/2021

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What is the Motor Cortex?

The brain contains many different important areas that perform unique functions. One of them is known as the motor cortex. This part of the brain is involved in planning and controlling voluntary motor movements. The motor cortex sends signals to the muscles in the body in order to generate and control movements. Meanwhile, the prefrontal cortex is involved in making executive decisions for the human brain.

Motor Cortex Location

The motor cortex is part of the frontal lobe of the brain. It is located on top of the brain in both left and right hemispheres where the frontal lobe meets the parietal lobe. It is located anterior, or in front of, the central sulcus and posterior to, or behind, the precentral gyrus.

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  • 0:00 Motor Regions of the Brain
  • 1:09 What Is the Primary…
  • 1:47 Primary Motor Cortex in Action
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Location of motor cortex

Location of motor cortex

Motor Cortex Components

There are three components or parts to the motor cortex in each hemisphere. They are known as the primary motor cortex, premotor cortex, and the supplementary motor area or SMA.

Primary Motor Cortex

Primary Motor Cortex

Premotor Cortex

Premotor Cortex

Supplementary Motor Area

Supplementary Motor Area

Motor Cortex Function

The function of the motor cortex is to plan, regulate, and execute voluntary motor movements. Motor function is described as any movement of the entire body or part of the body. Different types of motor movements and aspects of movements include:

  • preparation of movement
  • execution of movement
  • spatial navigation
  • sequences in movement
  • coordination between two sides of the body
  • transformation of multisensory inputs into motor outputs

The premotor cortex is specifically involved in controlling precision of movements in the human body.

Primary Motor Area

One of the main areas of the motor cortex is known as the primary motor area or cortex. This area of the brain is the powerhouse for any voluntary and skilled movements. The brain functions and processes all signals with the use of electrical signals or action potentials. Action potentials generated in the primary motor cortex result in movement of muscles on the opposite side of the body. It does this by receiving signals from the rest of the body and then coordinating muscular movements, such as walking and standing.

This area is located directly in front of, or anterior to, the central sulcus. It butts up against the parietal lobe of the brain dorsally, or on top. Another name for this area is the Brodmann area 4. The neurons in this area, known as Betz cells, send long axons down to the spinal cord. In the spinal cord, these axons make synapses with either interneurons or directly into alpha motor neurons. The interneurons then make synapse with cell body of motor neurons that send axons to the muscles in the periphery. Alpha motor neurons on the other hand send axons directly to those muscles without intermediate neurons.

Another very crucial component of this area is the way in which the control of body is mapped out on its surface. The motor control to body parts is mapped out in a very organized fashion along the central sulcus with the toe at the top and the mouth at the bottom. The amount of brain surface devoted to each body part is not proportional to the size of that body part. It is directly proportional instead to the density of receptors that body part contains, and inherently an increased number of receptors indicate the need for increased precision and acuity when generating movements of that body part. Thus, an increased amount of surface of the brain is devoted to those body parts i.e. hands and face. This map, or homunculus, in the primary motor cortex in each hemisphere controls the opposite side of the body.

Supplementary Motor Area

The supplementary motor area is another crucial part of the motor cortex. It is also located in the frontal lobe, just anterior to the primary motor cortex. This area of the motor cortex is involved in control of motor movements such as:

  • Control of posture during movement
  • Controlling coordination between body parts on both sides of the body
  • Controlling sequences of motor movements.

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Frequently Asked Questions

Where is the motor cortex?

The motor cortex is located in the frontal lobe anterior to the frontal sulcus where it meets the parietal lobe of the brain.

What contains the primary motor cortex?

The primary motor cortex is part of the frontal lobe of the brain. It is located at the top of the brain where the frontal lobe meets the parietal lobe.

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