Answered: What happens to contraction of a muscle…

Human Anatomy & Physiology (11th Edition)

11th Edition

ISBN:9780134580999

Author:Elaine N. Marieb, Katja N. Hoehn

Publisher:Elaine N. Marieb, Katja N. Hoehn

Chapter1: The Human Body: An Orientation

Section: Chapter Questions

Problem 1RQ: The correct sequence of levels forming the structural hierarchy is A. (a) organ, organ system,...

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Question

What happens to contraction of a muscle cell if some of the Ca2+ that was released during a contraction is still in the cytoplasm (sarcoplasm) when the next stimulus arrives?

- The muscle contracts with the same tension generated as during the first contraction, because the number of cross-bridges formed is always the same during a contraction.

- The muscle contracts with greater tension generated because more troponin molecules bound means greater myosin-binding sites (active sites) are revealed on the actin, leading to a larger number of cross-bridges formed.

- The muscle contracts with greater tension generated because there will be more Ca2+ in the sarcoplasm after the second stimulation, which will bind to more troponin molecules.

- The muscle contracts with the same tension generated as during the first contraction, because muscles contract in an all-or-none fashion.

Expert Solution

Step 1

Muscle contraction occurs by the generation of action potential which will reach the muscle fiber and start the contraction. The contraction starts with the release of calcium ions from the sarcoplasmic reticulum to the sarcoplasm. Calcium ions binds to the troponin on the actin filament and unmask the binding sites on actin filament for myosin. Hydrolysis of ATP will release energy which will make the binding of actin filament with myosin. This causes the sliding of actin filament over myosin filament and contraction happens.