CHAPTER XIV 

 GENERAL MUSCLE PHYSIOLOGY 



THE active movements of the body are produced by the 

 contraction of the muscles whose fibres shorten in their 

 longitudinal direction (contraction). They perform work 

 by the movement of the parts connected with them (bones). 



The physiology of the movement may be divided into: 



(1) General muscle physiology, the study of general properties 

 of muscles. 



(2) Special muscle physiology, which treats of the actions of 

 individual muscles. 



Anatomical considerations. The striated muscle is composed 

 of muscle fibres, varying in length up to 12 cm and having a 

 diameter of 0.01-0.06 mm. These fibres are surrounded and held 

 together by connective tissue (perimysium internum and ex- 

 ternum). In this connective tissue are found nerves and blood 

 vessels. The muscle fibre is composed of a bundle of parallel 

 fibrils, between which there is a protoplasmic substance, the 

 sarcoplasm. The fibre is surrounded by a structureless covering, 

 the sarcolemma. Directly beneath the sarcolemma lie the muscle 

 corpuscles, spindle-shaped and nucleated protoplasmic bodies. 



The smooth muscle is composed of fibre-like cells without any 

 sheath. The cells vary in length and diameter up to 0.5 mm and 

 0.02 mm respectively and contain rod-like nuclei. Sometimes 

 fibrils and sarcoplasma are found in smooth muscles. 



The fibrils which seem to contain the contractile part are, in 

 the smooth muscle, composed throughout their entire length of 

 doubly refracting parts (anisotropic), while the striated muscle 

 fibril is composed of alternate doubly and singly refracting 

 (isotropic) parts. The striated appearance of muscles is caused 

 by the alternate arrangement of parts which vary in transparency. 



In the middle of each isotropic (light) disk there is, in the 

 striated muscle, a narrow dark band called the intermediate disk, 

 or membrane of Krause, on both sides of which there is another 

 dark band called the secondary disk. In the centre of the aniso- 



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