All rights reserved. That Explains Some Symptoms Of PD Common sense tells us that for survival, feeding, play, work and reproduction precise control of movement is essential. Disruption of any of these functions by, for example, injury, disease and drugs can alter or stop normally precise movements.
Drugs generally have their effect at the synapse.
Some movements, called reflexes, are not complicated, appear to be built into the nervous system at very local site, and generally do not require fine control. Examples of protective reflexes include a simple action like quickly removing a hand from a hot object or closing of the eyelids when an object approaches. In the case of being burned, the electrical impulses from the pain receptors are also passed up the spinal cord to the cerebral cortex and into awareness. Also consider that emotions can influence movement. For example, when we are sad we may walk more slowly but when we are happy we may have a spring in our step.