This lesson explains how skeletal muscles produce tension to move loads or hold them still, and how the nervous system adjusts force by activating motor units.
Muscle tension is the force generated when muscle fibers contract. To move a load, sarcomeres in the muscle fibers shorten and generate enough force to overcome the load. Tension can also be produced when the load does not move.
All flashcards
What is an isotonic contraction?
A contraction in which muscle tension remains relatively constant while muscle length changes and a load moves.
How do concentric and eccentric contractions differ?
A concentric contraction shortens a muscle as it produces force. An eccentric contraction lengthens a muscle while it controls or resists a load.
What defines an isometric contraction?
The muscle produces tension without moving the load or changing the angle of the skeletal joint.
What is a motor unit?
One motor neuron together with all the skeletal muscle fibers that it innervates.
What is motor-unit recruitment?
The progressive activation of additional motor units to increase the force, or tension, produced by a muscle.
Quiz questions
At approximately what sarcomere length range can a skeletal muscle fiber produce near-maximal tension?Answer: About 80–120 percent of its resting length.
When does wave summation occur in a skeletal muscle?Answer: When a new stimulus arrives before the previous twitch has fully relaxed.
What distinguishes complete tetanus from incomplete tetanus?Answer: In complete tetanus, relaxation between contractions disappears.
What is treppe in skeletal muscle?Answer: A stepwise rise in contraction strength after repeated activation of a previously inactive muscle.
Which description best fits hypertonia?Answer: Excessive muscle tone, often associated with upper motor-neuron damage.
Based on Anatomy and Physiology 2e by J. Gordon Betts, Kelly A. Young, James A. Wise, Eddie Johnson, Brandon Poe, Dean H. Kruse, Oksana Korol, Jody E. Johnson, Mark Womble, Peter DeSaix (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.