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Chapter 11.5 Contraction of Skeletal Muscle

BOOK TITLE: Understanding Medical Physiology: A Textbook for Medical Students

Author
1. Bijlani R.L.
ISBN
9788180612213
DOI
10.5005/jp/books/10999_78
Edition
3/e
Publishing Year
2004
Pages
17
Author Affiliations
1. All India Institute of Medical Sciences, New Delhi
Chapter keywords
electrical phenomenon, mechanical process, excitation-contraction coupling, action potentials, sarcoplasmic reticulum junctions, cisternal membrane, contractile mechanism, functional significance, tropomyosin molecule, threshold stimulus, stretched condition, experimental situation, asynchronous activation, calcium channels

Abstract

This chapter discusses contraction of skeletal muscle, which means mechanical activation of the muscle. Calcium mediates the effect of excitation to the contractile proteins of muscle. The message of activation that a motor nerve fibre brings to a muscle fibre is expressed in the form of an action potential generated at the motor end plate. Relaxation is due to removal of calcium ions into the cisternae by active transport. An active calcium pump resides in the cisternal membrane which concentrates calcium ions in the cisternae. Myosin is the protein that constitutes the thick filaments. Actin is the major protein of the thin filaments. Tropomyosin is wrapped spirally around the actin filament. Tropomyosin extends the inhibition of one molecule of troponin to several active sites. Contractile elements are the filaments which bring about contraction through their rearrangement. Skeletal muscles are supplied by motor nerves. The maximal tetanic tension is higher than the maximal twitch tension.

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