Striated MusclesSkeletal and Cardiac Muscles
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal in Principles of Physiology for the Anaesthetist, 2020
Cardiac muscle functions as a syncytium due to the presence of low-resistance connections between adjacent cells, and when an action potential is generated, the atria or the ventricles contract together. The mechanical connections that prevent the cells from pulling apart include the desmosomes and fascia adherens. The T-tubules of the cardiac muscle are located at the Z lines, whereas they are positioned at the ends of the I-bands in skeletal muscle. Consequently, the T-tubule is linked with the terminal cisterna of the sarcoplasmic reticulum of only one sarcomere, forming a diad, rather than a triad, in the skeletal muscle. In striated muscle, the action potential propagates over the cell surface in a similar manner to nerves. Smooth muscles may show spontaneous activity, and the principal inwards current during depolarization is via calcium channels. Cardiac muscle cells have one nucleus and are made up of a network of branching fibres (syncytium) connected by intercalated discs that contain low-resistance gap junctions.
Electrocardiogram
Kayvan Najarian, Robert Splinter in Biomedical Signal and Image Processing, 2005
A cardiac muscle contraction is a direct result of the cellular electrical excitation described by the ECG. The depolarization initiates the shortening of each muscle cell. The electrical activation of each cell is an indication of its functioning. Therefore, the ECG is the result of depolarization of the heart muscle in a controlled repetitive fashion. By tracking the process of electrical depolarization of the cardiac muscle cells, an impression of the heart’s functionality can be formed and used to locate regions in the heart structure that are not functioning to specifications and may require medical attention. Any deviation from the typical ECG observed in the recorded electrical depolarization signal is analyzed and classified as a cardiac disorder.
Functions of the Cardiovascular System
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal in Principles of Physiology for the Anaesthetist, 2020
The cardiovascular system circulates blood through the vessels of pulmonary and systemic capillaries for the purpose of exchange of oxygen, carbon dioxide, metabolic nutrients, waste products and water in the tissues and in the lungs. It has an immune role, transporting antibodies and immune cells around the body. The heart is a muscular pump with four chambers: the right atrium and ventricle and the left atrium and ventricle. The pressures developed within the cardiac chambers determine the thickness of the muscle wall. The cardiac muscle cells are arranged in spiral layers anchored to the fibrous ring at the base of the heart, which encircle the chambers. The main substrate used by the heart is esterified and non-esterified fatty acid, which accounts for 60% of cardiac oxygen consumption. Cardiac muscle functions as a syncytium due to the presence of low-resistance connections between adjacent cells, and when an action potential is generated, the atria or the ventricles contract together.
Isoproterenol directs hair follicle-associated pluripotent (HAP) stem cells to differentiate
Published in Cell Cycle, 2016
Aiko Yamazaki, Masateru Yashiro, Sumiyuki Mii, Ryoichi Aki, Yuko Hamada, Nobuko Arakawa, Katsumasa Kawahara, Robert M. Hoffman, Yasuyuki Amoh
ABSTRACT Nestin-expressing hair-follicle-associated pluripotent (HAP) stem cells are located in the bulge area of the follicle. Previous studies have shown that HAP stem cells can differentiate to neurons, glia, keratinocytes, smooth muscle cells, and melanocytes in vitro. HAP stem cells effected nerve and spinal cord regeneration in mouse models. Recently, we demonstrated that HAP stem cells differentiated to beating cardiac muscle cells. The differentiation potential to cardiac muscle cells was greatest in the upper part of the follicle. The beat rate of the cardiac muscle cells was stimulated by isoproterenol. In the present study, we observed that isoproterenol directs HAP stem cells to differentiate to cardiac muscle cells in large numbers in culture compared to HAP stem cells not supplemented with isoproterenol. The addition of activin A, bone morphogenetic protein 4, and basic fibroblast growth factor, along with isoproternal, induced the cardiac muscle cells to form tissue sheets of beating heart muscle cells. These results demonstrate that HAP stem cells have great potential to form beating cardiac muscle cells in tissue sheets.
Cardiac Muscle in the Wall of an Anomalous Pulmonary Vein
Published in Pathology, 1971
An isolated cardiac muscle segment in an anomalous pulmonary vein is described. Pulmonary veins of twelve of seventeen randomly selected cases showed cardiac muscle continuous with the atria; no isolated segments were discovered. The segment of cardiac muscle is thought to have arisen by heteroplastic differentiation, and thus its presence does not add any weight to theories concerning the development of the pulmonary venous system. In view of this report careful study of the whole length of anomalous pulmonary veins would clearly be valuable.
Effects of exercise training on kinin receptors expression in rats with myocardial infarction
Published in Archives of Physiology and Biochemistry, 2017
Mei Shen, Min Yu, Jingya Li, Li Ma
Objectives: The objective of this study is to determine the role of kinin B1 and B2 receptors in exercise-induced cardiac muscle angiogenesis. Method: Thirty Wistar rats were randomly assigned to the control group, the myocardial infarction group and the exercise training group (myocardial infarction model was made and received 30 min exercise training on a treadmill). After 4 weeks of experiment, cardiac muscle was harvested. Results: B1 and B2 receptor mRNA and protein levels in the exercise-training group were significantly higher than those in the myocardial infarction group, which were higher than those in the control group. Capillary number in the cardiac muscle also showed the same tendency. There was a correlation between capillary number and B1 receptor protein (not B2 receptor protein) in the all groups. Conclusion: Kinin B1 and B2 receptors play roles in exercise-induced cardiac muscle angiogenesis. However, the B1 receptor appears to have a more prominent role.