voluntary muscle


noun Anatomy.

muscle whose action is normally controlled by an individual's will; mainly skeletal muscle, composed of parallel bundles of striated, multinucleate fibers.

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Origin of voluntary muscle

First recorded in 1780–90
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2020

HOMEWORK HELP

What are voluntary muscles?

A voluntary muscle is a muscle that you choose to move, like those in the arms and legs, as opposed to the ones that move automatically, like the heart.

Muscle is the tissue in animals that produces movement or motion. Voluntary means done out of free will or by choice. Voluntary muscles are also often called skeletal muscles (because all of the muscles attached to the skeleton are voluntary muscles) or striated muscles (because the muscle fibers make them look striated, or stripy).

Example: Around 40 percent of a human’s body mass is made up of voluntary muscles.

Voluntary muscle vs. involuntary muscles

Here’s a challenge: scratch your nose. Easy, right? Sure, but you still had to think about it—even if only for a split second. You had to decide to do it. That decision resulted in the movement of your arm and hand and finger (or your leg and foot and toe, if you’re very talented and weird) toward your nose thanks to voluntary muscles. 

Some muscles, like the muscles in your heart and in your guts, do their job all of the time without you having to even think about it. These are called involuntary muscles. But the voluntary muscles won’t do anything until your brain tells them to. Without voluntary muscles, animals wouldn’t be able to walk, run, fly, or swim. Voluntary muscles are typically longer and thicker than involuntary muscles and are made of cells that have more than one nucleus (which is basically a cell’s control center).

A voluntary muscle produces movement by contracting (drawing itself together) and relaxing (stretching itself out). Voluntary muscles require a lot more energy than involuntary muscles and remain relaxed when you’re not moving, such as when you’re asleep.

You may have noticed that people who use their muscles more have bigger, stronger muscles. This is because when the muscle gets used, it repairs the “damage” from that use by fusing the muscle fibers together. This type of muscle building is exclusive to voluntary muscles, since they can be moved at will.

Did you know ... ?

Sometimes, voluntary muscles move involuntarily—they expand or contract without “being told to,” which can cause pain or discomfort. These movements are called muscle spasms or cramps and can happen for a variety of reasons, such as poor stretching, muscle overuse, dehydration, or illness.

What are some real-life examples of voluntary muscle?

Usually, most voluntary muscles, such as the biceps in your arms or the quadriceps in your legs, are mentioned specifically by name in discussion of health or exercise. The general phrase voluntary muscle is more likely to be used in the study of anatomy.

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What other words are related to voluntary muscle?

Quiz yourself!

The large triceps muscle in the back of your arm doesn’t move by itself and won’t do anything until the brain tells it to. According to this description, is the triceps an example of a voluntary muscle?

Medical definitions for voluntary muscle

voluntary muscle

n.

A muscle, such as any of the striated muscles except the heart, whose action is normally controlled by individual volition.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.