As a result of the small size of cardiac muscle cells, the communication system described above (and in Chapter 13) is necessary for organized function. The small cell size also makes each cell more critically dependent on the external environment, and cardiac function may be greatly altered by electrolyte and metabolic imbalances arising elsewhere in the body. Hormonal messengers, such as norepineph-rine, also have quick access to cardiac muscle cells.
From a mechanical standpoint, the lack of skeletal attachments means cardiac muscle can function over a wide range of lengths. While the length-tension property is not of major importance in the functioning of many skeletal muscles, in cardiac muscle, it is the basis of the remarkable capacity of the heart to adjust to a wide range of physiological conditions and requirements.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.