Moving your limbs allows you to fully interact with your environment. You are able to pick up objects, wave to a friend and kick a ball if you want. But how does the brain communicate with the muscles? Movement is created and controlled by the precise interaction between motor regions of the brain, movement cells and chemical communication.
Planning and Executing Movement
The posterior parietal cortex and premotor brain regions initially plan movement. The posterior parietal cortex gathers sensory information to form a model that calculates where the body is relative to where you wish to move, or relative to the object you wish to pick up. This information is then sent to the premotor regions that plan movement timing, muscle force and movement sequence. The movement plan is then transferred to the primary motor cortex, an area of the brain that transmits the motor command down the spinal cord toward the muscles, according to Neuro 101.
Once the motor command reaches the desired spinal level, a nerve cell called an alpha motor neuron is stimulated in the spinal cord. The alpha motor neuron ultimately stimulates the muscle to contract, according to Neuro 101.
The alpha motor neuron extends toward the muscle, but does not actually touch it. Muscle is stimulated when special chemicals, called neurotransmitters, are secreted from the alpha motor neuron, according to Eastern Kentucky University.
Once the neurotransmitter is secreted from the alpha motor neuron, specialized channels open on the surface of the muscle that allow certain substances to flow into and out of the muscle. The flow of these substances, including sodium, potassium and calcium, cause the muscle fibers to contract, according to Neuro 101.
You rely upon sensory areas of your brain to execute movements correctly, especially when you are learning new types of movements such as, a dance, playing an instrument, or typing. Embedded within your joints are receptors that detect where your body is in space and embedded within your muscles are receptors that gage force and stretch. These types of information are sent to the primary sensory cortex. Information regarding how the movement was executed is also sent to the cerebellum, the large structure at the back of the brain. The cerebellum compares how the movement was performed versus how the movement should have been performed. If errors are detected, movement correction commands are sent to the primary motor cortex, to ensure that adjustments are made in the motor command, according to Principles of Neural Science.
- "Neuro 101: Neurophysiology Without Tears"; William MacKay; 1999.
- Eastern Kentucky University: Muscle
- "Principles of Neural Science"; Eric Kandel, James Schwartaz and Thomas Jessell; 2000