When exploring cardiac muscle, it's essential to consider various aspects and implications. 17.3: Cardiac Muscle - Medicine LibreTexts. Cardiac muscle cells undergo twitch-type contractions with long refractory periods followed by brief relaxation periods. The relaxation is essential so the heart can fill with blood for the next cycle.
The refractory period is very long to prevent the possibility of tetany, a condition in which muscle remains involuntarily contracted. It's important to note that, 17.3: Cardiac Muscle and Electrical Activity - Medicine LibreTexts. Recall that cardiac muscle shares a few characteristics with both skeletal muscle and smooth muscle, but it has some unique properties of its own.
This perspective suggests that, not the least of these exceptional properties is its ability to initiate an electrical potential at a fixed rate that spreads rapidly from cell to cell to trigger the contractile mechanism. Cardiac muscle tissue is only found in the heart. Highly coordinated contractions of cardiac muscle pump blood into the vessels of the circulatory system. Similar to skeletal muscle, cardiac muscle is striated and organized into sarcomeres, possessing the same banding organization as skeletal muscle (Figure 10 8 1 ).
17.3A: Mechanism and Contraction Events of Cardiac Muscle Fibers. Key Points Cardiac muscle fibers contract via excitation-contraction coupling, using a mechanism unique to cardiac muscle called calcium -induced calcium release. Excitation-contraction coupling describes the process of converting an electrical stimulus ( action potential ) into a mechanical response (muscle contraction). 17.3C: Energy Requirements - Medicine LibreTexts.
Cardiac muscle tissue has among the highest energy requirements in the human body (along with the brain) and has a high level of mitochondria and a constant, rich, blood supply to support its metabolic activity. Figure 17 3 1: Cardiac Muscle. (a) Cardiac muscle cells have myofibrils composed of myofilaments arranged in sarcomeres, T tubules to transmit the impulse from the sarcolemma to the interior of the cell, numerous mitochondria for energy, and intercalated discs that are found at the junction of different cardiac muscle cells. An intercalated disc allows the cardiac muscle cells to contract in a wave-like pattern so that the heart can work as a pump. Intercalated discs are part of the cardiac muscle sarcolemma and they contain gap junctions and desmosomes.
3.5: Muscle Tissue - Medicine LibreTexts. Muscle tissue is characterized by properties that allow movement. Muscle tissue is classified into three types according to structure and function: skeletal, cardiac, and smooth.
17.1F: Myocardial Thickness and Function - Medicine LibreTexts. The myocardium, or cardiac muscle, is the thickest section of the heart wall and contains cardiomyocytes, the contractile cells of the heart. Another key aspect involves, as a type of muscle tissue, the myocardium is unique among all other muscle tissues in the human body. The thickness of the myocardium determines the strength of the heart’s ability to pump blood.
In extreme cases, hypercalcemia can cause sustained muscle contraction or even cardiac arrest due to the inability of the muscle to relax. It's important to note that, on the other hand, hypocalcemia, a condition where blood calcium levels are too low, reduces the amount of calcium available for cardiac muscle contraction.
📝 Summary
Learning about cardiac muscle is important for individuals aiming to this area. The knowledge provided here works as a strong starting point for deeper understanding.