10: Spinal control of movement, brain control of movement

Motor control can be divided into two parts: the spinal cord’s command and the contraction of the muscles, and the brain’s control of the motor programs in the spinal cord. In the first chapter we discussed about the first type of motor control. 

There are smooth and striated muscles in out body. The striated muscles can be divided into cardiac muscle, which is the heart muscle, and the skeletal muscle, which enables us to move bones around our joints. The nervous system that controls our skeletal muscles is called somatic nervous system. Smooth muscles are found from digestive tract, arteries, and other structures that are innervated by the autonomic nervous system. Cardiac muscle is controlled by ANS as well. 

The motor neurons are divided into two categories; upper and lower motor neurons. The upper motor neurons of the brain supply input to the spinal cord, and the lower motor neurons initiate from the ventral horn and innervate the somatic musculature. These are called either alpha or gamma motor neurons. Alpha motor neurons generate the force in the muscles and make them contract, gamma neurons give input to the muscle spindle and innervate the intrafusal muscle fiber at the two ends of it instead. They play a role in contracting the muscles, keeping the muscle spindle taut.  

The upper motor neurons initiate from the motor cortex of the brain. Primary motor cortex is mostly responsible in initiating the movement, premotor area planning the movement and the posterior parietal motor cortex creates the idea of it. They leave the brain along different tracts. The descending pathways can be divided into the main pathways, which are lateral and ventromedial pathways. The first one includes mostly the tracts to do voluntary movements.

Alexandra & Alisa

 

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