11.1: Introduction

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Rosanna Hartline
West Hills College Lemoore

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Introduction

The best-known feature of skeletal muscle is its ability to contract and cause movement. Skeletal muscles act not only to produce movement but also to stop movement, such as resisting gravity to maintain posture. Small, constant adjustments of the skeletal muscles are needed to hold a body upright or balanced in any position. Muscles also prevent excess movement of the bones and joints, maintaining skeletal stability and preventing skeletal structure damage or deformation. Joints can become misaligned or dislocated entirely by pulling on the associated bones; muscles work to keep joints stable. Skeletal muscles are located throughout the body at the openings of internal tracts to control the movement of various substances. These muscles allow functions, such as swallowing, urination, and defecation, to be under voluntary control. Skeletal muscles also protect internal organs (particularly abdominal and pelvic organs) by acting as an external barrier or shield to external trauma and by supporting the weight of the organs.

Below are some important terminologies to be familiar with when learning about the skeletal muscles:

innervation: nerves present in the tissue (in this case, stimulating a muscle to contract)
contraction: the process of a muscle becoming shorter and tighter; caused by activated nerves
relaxation: the process of a muscle becoming longer and looser; caused by lack of activated nerves
action: a movement caused by muscle contraction
origin: the end of the muscle attached to a fixed (stabilized) bone
insertion: the end of the muscle that attaches to the bone being pulled/moved
tendon: strong fibrous tissue that attaches muscle to bone
prime mover / agonist: the principle muscle involved in a movement

Attributions

"Anatomy 204L: Laboratory Manual (Second Edition)" by Ethan Snow, University of North Dakota is licensed under CC BY-NC 4.0
"Anatomy and Physiology" by J. Gordon Betts et al., OpenStax is licensed under CC BY 4.0