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Cardiac physiology 

Cardiac physiology
Chapter:
Cardiac physiology
Author(s):

Rhys Evans

, Kenneth T. MacLeod

, Steven B. Marston

, Nicholas J. Severs

, and Peter H. Sugden

DOI:
10.1093/med/9780199204854.003.160103_update_002

Update:

This chapter has been extensively revised, and now includes content from retired Chapter 16.1.2.

Updated on 29 October 2015. The previous version of this content can be found here.
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date: 22 August 2018

The function of the heart is to provide the tissues of the body with sufficient oxygenated blood and metabolites to meet the moment-to-moment needs as dictated by physical activity and postural and emotional changes.

Cardiac myocytes are the contractile cells of the heart and constitute the bulk of heart mass. There are differences between the myocytes of the ventricles, the atria, and the conduction system: ventricular myocytes are elongated cells, packed with myofibrils (the contractile apparatus) and mitochondria (for ATP production). Myofibrils are repeating units (sarcomeres) made up of thin actin filaments anchored at the Z-discs at either end of the sarcomere, and thick myosin filaments which interdigitate and interact with the thin filaments. Contraction results from sarcomere shortening produced by the ATP-dependent movement of the thin and thick filaments relative to one another. Transverse (T-) tubules facilitate extracellular Ca...

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