The plane of any movement originates in the brain. The major part of the brain involved in the initiation and control of voluntary movement is the primary motor cortex. The motor neurons in the brain are called upper motor neurons (UMNs), while the motor neurons in the brainstem and spinal cord are called lower motor neurons (LMNs). UMNs are unable to leave the central nervous system; then they must synapse with LMN whose axons can leave the central nervous system, which allows them to synapse with muscles throughout the body. Therefore, in a normal situation, messages from the UMNs are transferred to the LMNs and from there they are transferred to specific muscles. The UMN and LMN are responsible for movements such as walking, chewing, and the movement of the arms, legs, chest, and face, respectively. This allows healthy individuals the ability to voluntarily move their muscles with ease. Amyotrophic lateral sclerosis is also called motor neuron disorder (MND), as it is characterized by continued degeneration of upper and lower motor neurons. These motor neurons, as stated earlier, are responsible for the voluntary muscles of the body, and when the neurons degenerate or die, the neurons are unable to send messages to the muscles. When muscles can no longer receive signals, they become unable to function and, in turn, become weak and worn out. Eventually, the brain loses the ability to initiate and control voluntary movement, resulting in paralysis. Because ALS only affects voluntary motor neurons, the senses (sight, smell, taste, hearing, and tactile sensations) are spared. Even involuntary motor neurons are not affected (e.g. the heart and digestive system). Furthermore, the individual is often not affected cognitively....... half of the article ...... iclesMitchell, J.D., and G.D. Borasio. 2007. Amyotrophic lateral sclerosis. Seminar. 369: 2031-2041. Roth-Kauffman, M. and J. Niebauer. 2012. Amyotrophic lateral sclerosis: diagnostic and appropriate management. Doctors' reviews. 22(7): 15-21Rowland, L.P. and N.A. Shneider. 2001. Amyotrophic lateral sclerosis. New England Journal of Medicine. 344(22): 1688-1700.Wijesekera, L.C. and P.N. Leigh. 2009. Amyotrophic lateral sclerosis. Orphanet journal of rare diseases. 4(3): doi:10.1186/1750-1172-4-3.WebpagesALS Association. About ALS. http://www.alsa.org/about-als/what-is-als.html. Updated 2010. Accessed March 13, 2014. National Institute of Neurological Disorders and Stroke. NINDS information page on amyotrophic lateral sclerosis (ALS). http://www.ninds.nih.gov/disorders/amyotrophylateralsclerosis/ALS.htm. Updated February 4, 2014. Accessed March 13, 2013.