Amyotrophic Lateral Sclerosis

AMYOTROPHIC LATERAL SCLEROSIS (ALS), commonly known as Lou Gehrig's disease, is a neurological disease that affects the motor neurons. There is no definitive test for the diagnosis of ALS, so it is one of exclusion, relying on signs and symptoms that pertain to dysfunction in both upper motor neurons (UMNs) and lower motor neurons (LMNs). There is only one treatment regularly used for the treatment of ALS, but it is not a cure. In general, ALS is diagnosed later than other disease processes in part because of the vague symptoms it can generate and also the time it takes for the physician to rule out other causes. The ultimate cause of death in ALS patients is the loss of muscle strength to properly breathe. The potential for stem cell research in playing a role in ALS treatment lies in the possibility of regenerating dead or dying motor neurons in the hopes of regaining muscle function and control.

Most neurons in the human nervous system are made up of dendrites, a cell body, and axons. The dendrites are responsible for receiving information, the cell body for processing that information and for creating products to be exported—such as neurotransmitters, and the axon for transmitting that information to other cells through the synapse previously mentioned. Because the axons are covered in a layer of fat called myelin, they have a white color. For that reason, areas of the central nervous system that are made up predominantly by axons are termed white matter. The cell bodies lack this fatty layer, and so they are gray. This is where the term gray matter comes from.

[Page 12]The human nervous system can be conceptually separated into two different functional halves. The first is the sensory system, responsible for receiving information from the environment and sending this information to higher centers for processing, such as the cerebral cortex. The other half of the human nervous system is the motor system.

The motor pathways in the nervous system are responsible for sending information from the central nervous system, comprising primarily the brain and spinal cord, out to the target organs and muscles to cause a response. The information in this outflow tract is carried by two neurons arranged in series connected by a synapse in the anterior aspect of the spinal cord. The first of these neurons starts in the motor strip, the autonomie nervous system centers, or other higher—processing centers, and they send fibers to the anterior aspect, or ventral horn, of the spinal cord. This first neuron is conventionally termed the UMN. It is in the ventral (anterior) horn that the UMN synapses, or connects, with the lower motor neuron LMN, which carries information from the spinal cord outward to its target. ALS is a disease that primarily affects the motor half of the nervous system.