Short Notes For Neet Disorders Of Muscular System
Muscle Diseases & Disorders
Muscle diseases or disorders are medical conditions, which affect the muscular system in our body. Primary muscular diseases originate directly from impairment of muscles, while secondary muscular diseases are caused by other diseases. Common features of these diseases include muscle weakness and atrophy (wasting of muscles). In this article, we will learn about some of the common muscle diseases, their causes, symptoms, and pathogenesis.
- Myasthenia Gravis
Myasthenia gravis is a neuromuscular disease that causes weakness in skeletal muscles. It is an autoimmune disease, in which the body’s own immune system attacks healthy cells.
The transmission of nerve impulses to muscles is disrupted at the neuromuscular junction due to the presence of antibodies. These antibodies can either alter, block, or destroy receptors for the neurotransmitter acetylcholine, resulting in impaired muscle contraction. In some cases, antibodies can be produced against other proteins such as muscle-specific-kinase.
It is often caused by the thymus gland, which remains large and active in adults or may develop tumors of the thymus gland.
Facial muscles are predominantly impacted by this condition, potentially causing drooping of the eyelids, double vision, difficulty swallowing, chewing, talking, etc. Onset can be sudden and, in more extreme cases, may lead to shortness of breath and even respiratory failure.
2. Muscular Dystrophy
Muscular dystrophy is a group of muscle disorders characterized by progressive wasting of muscles and weakening. It is a genetic disorder, which is either inherited or caused by mutation.
DMD, or Duchenne muscular dystrophy, is the most common type of muscular dystrophy, accounting for around half of all cases, and is one of nine main types of muscular dystrophy.
Duchenne Muscular Dystrophy (DMD) is an inherited X-linked recessive disorder caused by a defect in the gene coding for dystrophin. Dystrophin is a protein found in muscle fibers that acts as a shock absorber and provides mechanical stabilization. Additionally, it regulates the calcium ion levels, which are necessary for muscle contraction.
The gene for dystrophin is located on the X chromosome. Since males have only one X chromosome, if the gene is defective, it can lead to a lack of protein dystrophin, resulting in muscle degeneration and ultimately death. This makes the disease more common in males.
Females are more likely to be carriers of the disease due to their possession of a pair of X chromosomes. This means that even if one of the chromosomes contains a defective gene, the other is still able to provide the necessary proteins. Generally speaking, it is not possible for females to have both X chromosomes with defective genes, as males with this condition typically do not survive long enough to become reproductively active.
Muscle weakness typically begins with the upper arms and legs, and worsens over time, eventually affecting other parts of the body. This can make even simple tasks difficult to complete. Ultimately, it can lead to heart and respiratory complications, shortening the lifespan.
- Tetanus
Tetanus is caused by a bacterial infection of Clostridium tetani. It is also known as ’lockjaw’ and is characterized by painful muscle contractions or spasms.
The bacterium is present in dust, soil, and manure, and enters the body through a cut or wound in the skin or puncture by a contaminated object. It releases a toxin that interferes with normal muscle contractions and causes spasms.
Tetanus neurotoxin (TeNT) blocks the release of neurotransmitters from inhibitory neurons, leading to an uncontrolled firing of motor neurons and difficulty in muscle relaxation. This causes spasms and spastic paralysis.
Mostly, spasmodic episodes begin in the jaw, making it hard to open the mouth or swallow. These spasms can spread to other parts of the body, sometimes being so strong that they can even cause fractures. Other signs of spasmodic episodes include fever, headache, sweating, high blood pressure and an increased heart rate.
Vaccination can help prevent the disease.
4. Tetany
Tetany is a metabolic disorder characterized by involuntary and sustained muscle contractions. It is primarily caused by calcium deficiency or hypocalcemia.
The parathyroid gland not functioning properly may be a cause of spasms. Additionally, low levels of potassium (hypokalemia) and magnesium (hypomagnesemia) can also lead to spasms.
Symptoms of the condition include:
- Muscle twitching
- Cramping
- Pain
- Spasms of the larynx
- Vomiting
- Convulsion
- Breathing difficulties
