Vocabulary of Muscle Tone Disorders Video

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  • 0:01 Muscle Tone
  • 0:49 Hypertonia, Myotonia,…
  • 2:21 Hypotonia & Atonia
  • 3:15 Lesson Summary
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Lesson Transcript
Instructor: Artem Cheprasov
Are you toned? Do your muscles have normal tone? Are they even the same thing? This lesson defines muscle tone, hypertonia, hypotonia, dystonia, and other terms related to muscle tone.

Muscle Tone

When it comes to athletes, some are skinny and toned, like long distance runners. Others are really big and anything but toned, like many of the world's strongest men competitors. And then, there are the really big and toned guys, or more properly, ripped, like those in Mr. Universe.

But that kind of toned, the look to a muscle, has little to do with the technicalities of muscle tone, a.k.a. tonus, the normal state of balanced muscle tension in the body that makes things such as posture, movement, and coordination possible.

This lesson is going to discuss some terms related to muscle tone, especially words describing improper muscle tone that can arise as a result of everything from damage to the central nervous system, to infections, to the ingestion of toxins.

Hypertonia, Myotonia, and Dystonia

Imagine a really stiff rubber band, one that is hard to move or stretch out. This is like hypertonia, abnormally increased tension of the muscle, where 'hyper-' implies an abnormal increase in something. The 'ton-' means 'tone,' as in muscle tone in our case, and '-ia' is a state or condition of something. So we get the state or condition of abnormally increased muscle tone.

Hypertonia makes it difficult to walk; it feels like everything is stiff. This can actually 'freeze' a joint in place because the muscles around it are so inflexible. All of this can make it so difficult to walk, people will simply fall, especially if something causes them to go off-balance.

You see, normally, a person is able to quickly extend or flex their muscles to catch themselves if they are off-balance and about to fall down. We may move a foot one way or another or swing our arms to avoid falling. But people with hypertonia cannot move those muscles out fast enough to do what a normal person can, and so they are more susceptible to a fall as a result.

Similar in a sense to hypertonia is myotonia, the delayed relaxation of a muscle after contraction. The 'myo-', in myotonia, means 'muscle.' Myotonia is like you squeezing a stress ball down to a small size with your hand and it taking forever to relax back into shape.

Also having to do with contraction is dystonia, the usually sudden and involuntary movement and prolonged contraction of one or more muscles, which results in tremors, abnormal postures, or twisting body motions.

Hypotonia & Atonia

Exactly the opposite of hypertonia, sort of like when a rubber band is too lax and too stretchy, is hypotonia, a condition characterized by abnormally diminished muscle tone. 'Hypo-' implies an abnormally decreased amount of something.

For example, in the case of infants with hypotonia, they will seem very limp and floppy. They will have difficulty holding their head up because their muscles can't contract properly to give the neck and head the strength to remain upright or upright for long.

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