regular cardiac myocyte regular atrial cardiac myocyte 2010-08-23T11:41:03Z Regular atrial cardiac myocytes, also known as atrial myocytes, are specialized muscle cells found in the atria – the upper chambers of the heart. They contract and relax during the heart's cycle, modulating the pumping of blood through the atria and into the ventricles. Additionally, endowed with inherent rhythmic electrical activity, atrial myocytes contribute significantly to the initiation and propagation of the heart’s electrical impulses. A distinguishing feature that separates atrial myocytes from other cardiac myocytes is their ability to synthesize and secrete atrial natriuretic peptide (ANP) in response to atrial stretch or dilatation. ANP acts as a potent vasodilator and diuretic, helping to maintain blood pressure and volume homeostasis. The phenomena of atrial stretch or distension, which triggers ANP release, is often in response to excess blood volume entering the heart, providing a mechanism at the cellular level which actively regulates systemic cardiovascular balance. Like all cardiac myocytes, atrial myocytes are embedded in a dense network of connective tissue that provides structural support. These cells are characterized by a single, centrally located nucleus, and overall, have a rod-like appearance with branching ends that connect with adjacent cells to form a continuous, synchronized ensemble. Their cytoplasm is abundant with mitochondria, reflecting the high energy demand associated with constant contraction and relaxation. At the ultrastructural level, atrial myocytes display striations due to the regular arrangement of actin and myosin proteins, which facilitate the contraction process essential for the heart's pump function. (This extended description was generated by ChatGPT and reviewed by the CellGuide team, who added references, and by the CL editors, who approved it for inclusion in CL. It may contain information that applies only to some subtypes and species, and so should not be considered definitional.) FMA:83108 atrial myocyte Regular cardiac myocyte of a cardiac atrium. atrial cardiac muscle cell regular cardiac muscle cell of atrium regular atrial cardiac muscle fiber