Source: Tetanus; Public Domain: http://en.wikipedia.org/wiki/File:Opisthotonus_in_a_patient_suffering_from_tetanus_-_Painting_by_Sir_Charles_Bell_-_1809.jpg
Welcome to this lesson on disorders of the muscular system. Today, we will be identifying the description and causes of various disorders of the muscular system. So let's start here with muscle strains.
So the description of a muscle strain is when a muscle fiber tears or is stretched too far. So sometimes this tear can be a small tear, which is very minor and will heal quickly on its own. But sometimes, if the tear is complete, that muscle might lose some of its functionality. So there's a little bit of a spectrum there on how serious this type of disorder can be, how serious a strain can be. So it can either be a small tear all the way to a complete tear. And common causes of this are overuse or sports injuries.
Our next disorder are cramps and spasms. So a spasm is a muscle cramp that does not immediately release. And a muscle cramp is an involuntary contraction of a myself. So when a muscle contracts involuntarily, we call that a spasm. And when that spasm doesn't release, we call it a cramp.
So if you've ever had something called a charley horse before, you have experienced a muscle cramp or a spasm that doesn't immediately release. And a common cause for this is actually potassium deficiency. So potassium is needed for nerve impulses to propagate properly. So if somebody has a potassium deficiency in their diet, it can cause muscle spasms or cramps.
Muscular dystrophy is our next disorder that we're going to discuss here. And this is when skeletal muscles break down and become weakened. So DMD, which stands for Duchenne's muscular dystrophy-- so DMD, Duchenne muscular dystrophy, is one of the types of muscular dystrophy where sarcomeres don't properly contract. So this type of muscular dystrophy-- most people who have this type will die in their early 20s, and prior to that will probably be using a wheelchair. So it's a very serious type of muscular dystrophy that's most common, as I said, in children because most people don't live past the age of 20.
And then the other type of muscular dystrophy that we have is myotonic muscular dystrophy. So this type of muscular dystrophy is more common in adults. And it's not deadly, and usually will only affect the hands and feet. So it's not as serious as Duchenne muscular dystrophy, but it still does have some limiting effects on the person who has it. And the cause of this is genetics. It's a genetic disorder.
Tetanus is our next disorder. And this is when muscles experience continual contractions, which can lead to death if the paralysis reaches the person's heart. So this is also sometimes referred to as lockjaw. That's another name for tetanus. There is now a vaccine for tetanus that most people have that prevents the disease. So you're protected by the vaccine.
So basically the way that this type of disorder is transmitted is through microbes. So a bacterial toxin which is found in soil containing cattle or horse manure will enter a wound. And then that will cause you to have exposure to tetanus. If that microbe is in that soil containing that manure. And then what it will do is inhibit your nervous system signals to the muscular system. So your nervous system and your muscular system will not be properly communicating, which causes those continual contractions and can lead to death.
And our last disorder we're going to talk about is atrophy. So this is described as the wasting away of muscle tissue. The one nice thing about this disorder is that it actually can be reversed. So oftentimes, people who experience this disorder are people who are on bed rest due to an illness or injury.
So when you're on bed rest due to illness or injury, you're not using your muscles. So there's a lack of use of muscles. And so those muscles will start to waste away over time. But if that person is off of bed rest or able to get up, start using their muscles again, they can actually reverse this disorder. So this lesson has been an overview on various disorders of the muscular system.
Muscle fiber tears or stretches too far.
An involuntary muscle contraction often caused by potassium deficiencies.
A genetic disorder that causes the gradual breakdown of muscle fibers.
A disease caused by microbes that causes muscles to continually spasm.
The wasting away of muscle tissue leading to very weak muscles.