Physiology and biochemistry in modern medicine (1918) (14594527468)

Identifier: physiologybioche00macl (find matches)

Title: Physiology and biochemistry in modern medicine

Year: 1918 (1910s)

Authors: Macleod, John James Rickard, 1876-1935 Pearce, R. G. (Roy Gentry), 1884-

Subjects: Physiology Biochemistry

Publisher: St. Louis : Mosby

Contributing Library: Columbia University Libraries

Digitizing Sponsor: Open Knowledge Commons

Text Appearing Before Image:

A.—Skeletal Muscle

Text Appearing After Image:

B.—Cardiac Muscle Fig. 45.— Effects of stimuli of increasing strength on skeletal and cardiac muscle to illustratethe all or nothing principle in the latter. i From Practical Physiology.) mal effect, whereas in skeletal, the effect, as measured by the height ofcontraction, is proportional to the intensity of stimulation. This is some-times known as the all or nothing phenomenon (Fig. 45). 2. If maximal stimuli are applied successively and at short intervalsof time to skeletal muscle, a slightly higher response results from eachsucceeding stimulus, until about ten stimuli have been applied, afterwhich for some considerable time the same height of contraction followseach stimulus. If each contraction is recorded, it will be seen that thefirst few contractions give a staircase effect; that is, if a horizontal line isdrawn from the top of each contraction to the next one, the effect of a 178 THE CIRCULATION OF THE BLOOD staircase with gradually diminishing steps will be produced. If w

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1918

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