LECTUEE VII 

 MUSCULAR SYSTEM 



The peculiar property of muscle tissue is the power of self- 

 contraction and self -movement. The muscles of the animal body 

 are of three kinds, voluntary, involuntary, and heart muscle. 



Involuntary muscles act independently of the will, and are 

 under the control of the sympathetic and cerebrospinal nervous 

 systems. 



Voluntary muscles are under the control of the will through 

 the cerebrospinal nervous system. 



Heart muscle is not under control of the will but is similar 

 to voluntary muscle in structure. 



Voluntary muscles. — What is popularly termed "lean meat" 

 is composed of voluntary muscles. These are classified into 

 simple, digastric, biceps, triceps, penniform, bipenniform. The 

 belly is the active working part (lean meat). The tendon is a 

 strong cord or band of white connective tissue. This merely 

 serves to give connection with a distant object, usually a bone. 

 Tendons are strong, but have no power of contraction. The 

 strength of a muscle depends upon the thickness of the belly. 

 The extent of its movement depends upon the length of the 

 belly. 



The two ends of a muscle are denned as origin and insertion. 

 The origin is the less movable end; insertion the more movable 

 end. It may happen at one time that one end is the insertion, 

 at another time the origin. 



A simple muscle is characterized by a single belly with not 

 more than one tendon at either end ; a digastric muscle has two 

 bellies connected by a tendon; a biceps muscle has two tendons 

 at one end ; a triceps muscle has three tendons at one end. 



They are also classified according to function into flexors, 

 extensors, abductors, adductors, and rotatftrs. 



Muscles are paired in a double sense. The rule is that for 

 any given muscle there is a corresponding muscle on the other 



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