The muscular system, consisting of muscles that are attached to bones via tendons, produces movement through well-coordinated contractions of muscle groups. Not only do humans depend upon the muscular system to get around, muscles also assist with venous blood return to the heart and the function of the immune system through aiding in lymphatic flow. Diseases of the muscular system produce pain and affect an individual's ability to move.
Features
Most muscular diseases also involve the motor neurons, which are part of the nervous system. While the muscles themselves are composed of contractile cells, all the body's skeletal muscles--that is to say, muscles under voluntary control--depend upon stimulation by the motor neurons in order to contract. Diseases may affect the motor neurons, the connection between motor neurons and muscle cells, or the muscle cells themselves, and still be classified as muscular diseases.
Genetic Diseases
Some muscular diseases are genetic. One of the best-studied of the muscular diseases is muscular dystrophy, a genetic disorder. Muscular dystrophy is the product of an error in an individual's genetic code, or DNA, explains the National Institute of Neurological Disorders and Stroke. That means that though the disorder may not cause symptoms from the time of birth, it's nevertheless present throughout life. Symptoms include degeneration of the muscles and loss of strength, leading to loss of movement. Typically, the disease progresses throughout life, meaning that as an individual ages, her symptoms worsen with time. The institute notes that while there is currently no treatment for muscular dystrophy, patients may benefit from physical therapy, strengthening activities and activities that promote muscle coordination.
Acquired Diseases
Other muscular diseases don't have a clearly delineated genetic cause. Amyotrophic lateral sclerosis, or Lou Gherig's Disease, is a very severe degenerative disorder that appears to occur randomly. The National Institute of Neurological Disorders and Stroke notes that most patients with the disease don't have family histories indicating susceptibility and don't share a common genetic mutation that might cause the disease. Further, there is no evidence of the disease being the result of an infectious agent. Patients typically develop amyotrophic lateral sclerosis later in life--after age 40--and symptoms generally start either at the feet or, more rarely, at the top of the head. Weakness and paralysis progress up or down the body, eventually leading to paralysis of the respiratory muscles. There is no cure for the disease, though some drug therapies may prolong life by a matter of a few months.
Diseases With No Clear Etiology
Still further muscular diseases may have any number of causes. Fibromyalgia, for instance, is still a bit of a medical conundrum, but it appears that it may be the result of several potential triggers. MayoClinic.com notes that some sufferers may have a genetic predisposition to the disorder, while others acquire fibromylagia after an infection or as the result of severe stress. Symptoms include pain and tenderness throughout the muscular system and in the joints, with pain often escalating at certain times of the day or during particular seasons of the year. There is no real cure for fibromyalgia, though some patients find that analgesic drugs, and even certain anti-seizure medications may help relieve symptoms. Since the disease appears to have some contingent of emotional involvement, physicians may also prescribe psychological counseling to patients.
Expert Insight
While the heart is made of muscle, it's only loosely considered a part of the muscular system. Many muscular diseases don't affect the heart--though some can--and many diseases of the heart have no effect upon the other muscles. This is due largely to differences in the way the nervous system communicates with the heart as opposed to the skeletal muscles. Explains Dr. Gary Thibodeau in his book, "Anatomy and Physiology," the heart is one of very few auto-contractile muscles in the body, meaning that it contracts, or beats, without neural input. As such, diseases of the motor neurons don't affect the heart.
References
- National Institute of Neurological Disorders and Stroke: Muscular Dystrophy
- National Institute of Neurological Disorders and Stroke: Amyotrophic Lateral Sclerosis
- MayoClinic.com: Fibromyalgia
- "Anatomy and Physiology;" Gary Thibodeau, Ph.D.; 2007
