Your body has about 5.6 liters of blood. All of this blood circulates through the body three times every minute. In one day, the blood travels a total of 12,000 miles (NOVA). Rhythmic contractions of the heart pump blood occur in response to electrical control pulse sequences. Active cells in the sinoatrial node in the heart trigger a sequence of electrical events that control muscle contractions, which pump the blood.
Scientific interest in the heart goes back centuries. Some of the most basic understandings about the operation and specifically the electrical currents of the heart were discussed during the May 17, 1888 Proceedings of the Royal Society of London by Professor J.A. McWilliam of the University of Aberdeen. The following conclusions were based on his studies of mammalian hearts in cats, dogs, rabbits, rats, hedgehogs, and guinea-pigs.
* An all or nothing approach to heart contraction
o If a stimulus was strong enough to excite contraction, it produced a maximal contraction
* The application of interrupted currents induces fibrillar contractions which can be recovered from even after long period under the combined influence of artificial respira...
... middle of paper ...
...n that prevents the heart from immediately contracting again.
1. "Cactus Picture"
2. Campbell, Neil A. (2002) "Biology" 6th edition. Benjamin Cummings. San Francisco, CA.
3. Kay, Ian. (1998) "Introduction to Animal Physiology" Springer-Verlag New York Inc.
4. McWilliam, J.A. (1888) "On the Rhythm of the Mammalian Heart" Froceedings of the Royal Society of London, Vol. 44, pages 206-208.
5. NOVA. " Cut to the Heart” PBS Online
6. Pool, Robert. (1990) “Heart Like a Wheel” Science, Vol. 247, No. 4948, pages 1294-1295.
7. Putnam, Jeremiah L. "Heart Diagram" Professor of Biology. Davidson College.
8. Schmidt-Nielsen, Knut. (1997) "Animal Physiology: Adaptation and environment" Fifth Edition. Cambridge University Press. New York, NY.
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