Final answer:
The four connexin isoforms expressed in the heart are connexin43 (Cx43), connexin45 (Cx45), connexin40 (Cx40), and connexin37 (Cx37), which are crucial for the formation of gap junctions necessary for synchronized heart contractions.
Step-by-step explanation:
The four connexin isoforms expressed in the heart are connexin43 (Cx43), connexin45 (Cx45), connexin40 (Cx40), and connexin37 (Cx37). These connexins are critical for forming gap junctions in the cardiac muscle. Gap junctions facilitate the efficient transmission of electrical signals necessary for synchronized heart muscle contractions, as they connect heart muscle cells, allowing them to contract in tandem. This electrical signal coordination is essential for maintaining a consistent heart rhythm and is managed within the heart's conduction system, which includes the sinoatrial (SA) node, atrioventricular (AV) node, and internodal pathways.