PhysiologyLesson 3 of 9 in the course Muscle Tissue

Skeletal Muscle Contraction, Energy, Relaxation, and Structural Change

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

This lesson follows the signal that starts contraction and explains how calcium makes contraction possible. It also introduces the sarcomere, the repeating unit where muscle filaments move.

A skeletal muscle fiber contracts after a motor neuron releases the neurotransmitter acetylcholine (ACh) at the neuromuscular junction. ACh initiates a change in the muscle fiber membrane, or sarcolemma. Sodium ions (Na+Na^+) enter the fiber, causing local depolarization. If the signal reaches threshold, an action potential spreads along the sarcolemma.

All flashcards

Excitation-contraction coupling
The sequence connecting a muscle fiber action potential to calcium release and the start of contraction.
Power stroke
The pivoting movement of a myosin head that pulls a thin filament toward the M-line.
Oxygen debt
The extra oxygen needed after exercise to restore the body to its pre-exercise condition.
Hypertrophy
An increase in muscle fiber size associated with more contractile material within the fibers.
Dystrophin
A protein that helps connect myofibril thin filaments to the sarcolemma.

Quiz questions

  1. What happens when ATP binds to a myosin head attached to actin?Answer: The myosin head detaches from actin.
  2. What reaction does creatine kinase catalyze during rapid ATP regeneration?Answer: Transfer of a phosphate group from creatine phosphate to ADP.
  3. What does oxygen debt refer to after intense exercise?Answer: The extra oxygen needed to restore the body to its pre-exercise condition.
  4. How does insufficient dystrophin contribute to muscle damage in Duchenne muscular dystrophy?Answer: It weakens the connection between myofibrils and the sarcolemma, making the membrane vulnerable to damage.
  5. Which statement best describes muscle fatigue?Answer: It is the inability of a muscle to keep contracting in response to nervous-system signals.

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.

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