CHAPTER 40 



Circulation in skeletal muscle 



HENRY BAR CROFT 



Sherrington School of Physiology, St. Thomas Hospital 

 Medical School, London, England 



CHAPTER CONTENTS 



Basal Tone 

 Automaticity 



Automaticity in Human Muscle Vessels 

 Pressure-Flow Relations in Muscle Vessels Deprived of 



Automaticity 

 Critical Closing Pressure 

 Local Temperature 

 The Problem of Structure and Function 

 Nervous Control 



Sympathetic Vasoconstrictor Nerves 



Effect of sympathetic vasoconstrictors upon resistance, 

 blood volume, and capillary filtration in skeletal muscle 

 vessels 

 Chemical transmission at sympathetic vasoconstrictor 



nerve endings in skeletal muscle 

 Effect of stimulation of the arterial baroreceptors on 



skeletal muscle vessels in the dog 

 Effect of stimulation of the arterial baroreceptors on the 



circulation in human skeletal muscle 

 Effect of receptors in a low pressure area in the cardio- 

 pulmonary system on the sympathetic vasoconstrictor 

 tone in human skeletal muscle 

 Impulse frequency in sympathetic vasoconstrictor fibers 

 Sympathetic Vasodilator Nerves 



Chemical transmission at sympathetic vasodilator nerve 



endings in skeletal muscle 

 Activation of sympathetic vasodilator fibers to skeletal 



muscle by hypothalamic stimulation 

 Sympathetic vasodilator fibers to human skeletal muscles 

 Do Posterior Root Fibers Affect Muscle Blood Flow? 

 Effect of the Temperature-Regulating Center on the Circula- 

 tion in Muscle 

 Role of Sympathetic Fibers to Muscle in Exercise 

 Action of Sympathomimetic Substances 

 Noradrenaline 

 Adrenaline 



Effect of Adrenaline on the Circulation in Skeletal Muscle 

 During Exercise 

 Reactive Hyperemia 

 Exercise Hyperemia 



few will deny that analytical study of the physiology 

 of the circulation in skeletal muscle began in the 

 Institute of Physiology at Leipzig. The paper bears 

 the name of Gaskell (108), but it was Carl Ludwig 

 who suggested the problem and who probably did 

 many of the experiments. In Gaskell's Obituary 

 Notice written by Langley (137) we read — "At this 

 time Ludwig's laboratory was much the most im- 

 portant school of physiological research in Germany 

 or elsewhere. It attracted students from all parts of 

 the world. All the work was planned by Ludwig, 

 who had an almost unerring sense of the lines of 

 work which would yield profitable results. To this 

 the success of the school was mainly due. Its popu- 

 larity was increased by the method of procedure 

 adopted by Ludwig. This has been described by T. 

 Lauder Brunton who was with Ludwig in 1869-70. 

 The experiments were carried out by Ludwig with 

 the pupil as an assistant, Ludwig wrote the paper 

 and then published it, occasionally as a conjoint 

 work, but usually in the name of his pupil. As I have 

 heard from Gaskell the method was the same in his 

 time." 



Be that as it may, let us turn to the experiments 

 themselves — "On the changes of the blood stream in 

 muscles through stimulation of their nerves." By a 

 simple graphical method venous outflow was recorded 

 from the extensor group of muscles of an unanesthe- 

 tized dog. The changes in outflow were determined 

 during and after tetanic stimulation of the crural 

 nerve. From a typical record, such as that seen in 

 figure 2 (top), six phases could be discerned during 

 sustained contraction : a) an initial spurt due to 

 squeezing of the veins by the muscles; b) decrease in 

 flow caused to some extent by mechanical compres- 

 sion of the vessels by the contracted muscle; c) in- 



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