anatomy

An Introduction to Skeletal Muscles: Properties and Physiology

The muscular system allows us to move and do our daily tasks. It also provides heat, stability, and blood flow for our body. There are three main types of muscular tissue: cardiac muscle, which comprises the heart muscle, smooth muscle, which comprises the linings of organs, and skeletal muscle, which are the muscles that help our body move. This article will focus on the physiology of skeletal muscles.

General Properties of Muscle Tissue

Before we even talk about skeletal muscles, there are some general properties of muscle tissue. All muscle tissue has four factors in common: excitability, elasticity, extensibility, and contractility. 

  1. Muscle cells have the ability to change the electrical state of their membrane, which is called excitability. This is influenced by signals from the nervous system and hormones from other cells. When muscle cells are “excited”, they create an electrical impulse called an action potential, which starts the muscle action.
  2. Extensibility is what allows muscle cells to stretch and gives our muscles the flexibility to move. 
  3. Elasticity is the ability of muscle cells to return back to its original physical shape after being stretched. Think of stretching a rubber band and then letting go. This property is crucial in muscle cells because it allows us to keep using our muscles in repetition.
  4. Contractility is the ability of muscle cells to pull and contract with force. It is important to remember that muscles never push, only pull. 

Now that we understand  these four factors of muscle tissue, we can dive into how skeletal muscles contract. 

Basics of Skeletal Muscle

Skeletal muscles are attached to our skeleton at two points that we call the origin and the insertion. The origin of muscle is fixed, meaning that it does not move. The other end of the muscle, the insertion, does move the bone that it is attached to. Some muscles may have more than one origin, such as the biceps brachii, which have two origins. 

In the human body, there are over 650 named skeletal muscles. Although this number may seem like a lot, skeletal muscles actually rely on each other to perform their function. In every muscular action, there is a prime mover, which is the main muscle. Prime movers are also called agonist muscles. Agonists have helper muscles called synergists. Every action also has an antagonist muscle that works directly in opposition to the agonist muscle. Antagonist muscles are equally as important as agonist muscles because they provide stability and maintain correct posture. Actions can be reversed, in which case the terms for agonist and antagonist are also reversed. For example, the action of bending (flexing) the arm is primarily moved by biceps brachii (the agonist), while the triceps brachii (the antagonist) acts against the biceps brachii. However, for the action of extending the arm, the triceps brachii becomes the agonist while the biceps brachii becomes the antagonist. 

AgonistSynergistAntagonist
RolePrimary muscleHelper muscleOpposition Muscle

Clearly, our muscular system is not as simple as just a collection of tissue that helps us move. There are many mechanisms involved within our muscles that ultimately allow us to do the things we take for granted. So, the next time you are working out, remember to thank your muscular system.

Works Cited

OpenStax College. “Anatomy & Physiology”. OpenStax College. 25 April 2013. <http://cnx.org/content/col11496/latest/

“Describing Skeletal Muscles: A Review of Muscle Attachments And Actions”. Visible Body. <https://www.visiblebody.com/learn/muscular/muscle-movements>

“FUNCTIONS AND PROPERTIES OF MUSCLE TISSUE”. Brigham Young University. <https://content.byui.edu/file/a236934c-3c60-4fe9-90aa-d343b3e3a640/1/module7/readings/function_muscle_tissue.html>

“Muscle Roles and Contraction Types”. PT Direct. <https://www.ptdirect.com/training-design/anatomy-and-physiology/skeletal-muscle-roles-and-contraction-types>

“Muscular Tissue”. Lumen Learning, Boundless Anatomy and Physiology. <https://courses.lumenlearning.com/boundless-ap/chapter/muscular-tissue/

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4 replies »

  1. This article is clearly written and organized in such a logical manner that it makes it easy for the general reader to follow. She handles the naming of specific muscles and their functions in such a way that the terminology is not intimidating. I really liked the rubber band analogy because it made it easy for me to visualize the process. Good job!

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  2. This article is well-written and logically organized, which renders it accessible to a general reader like me. I am impressed with the way the terminology is presented because she does so in such a way that makes it less intimidating. To the same end, the rubber band analogy is perfect because it allows me to visualize the action being described. Good job!

    Like

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