Rigor mortis, or postmortem rigidity, is the fourth stage of death. It is one of the recognizable signs of death, characterized by stiffening of the limbs of the corpse caused by chemical changes in the muscles postmortem. In humans, rigor mortis can occur as soon as four hours after death. Contrary to folklore and common belief, rigor mortis is not permanent and begins to pass within hours of onset. Typically, it lasts no longer than eight hours at "room temperature".
Smooth muscle is an involuntary non-striated muscle, so-called because it has no sarcomeres and therefore no striations. It is divided into two subgroups, single-unit and multiunit smooth muscle. Within single-unit muscle, the whole bundle or sheet of smooth muscle cells contracts as a syncytium.
Skeletal muscles are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscle tissue, and are often known as muscle fibers. The muscle tissue of a skeletal muscle is striated – having a striped appearance due to the arrangement of the sarcomeres.
A sarcomere is the smallest functional unit of striated muscle tissue. It is the repeating unit between two Z-lines. Skeletal muscles are composed of tubular muscle cells which are formed during embryonic myogenesis. Muscle fibers contain numerous tubular myofibrils. Myofibrils are composed of repeating sections of sarcomeres, which appear under the microscope as alternating dark and light bands. Sarcomeres are composed of long, fibrous proteins as filaments that slide past each other when a muscle contracts or relaxes. The costamere is a different component that connects the sarcomere to the sarcolemma.
Cardiac muscle is one of three types of vertebrate muscle tissues, with the other two being skeletal muscle and smooth muscle. It is an involuntary, striated muscle that constitutes the main tissue of the wall of the heart. The cardiac muscle (myocardium) forms a thick middle layer between the outer layer of the heart wall and the inner layer, with blood supplied via the coronary circulation. It is composed of individual cardiac muscle cells joined by intercalated discs, and encased by collagen fibers and other substances that form the extracellular matrix.
Striated muscle tissue is a muscle tissue that features repeating functional units called sarcomeres. The presence of sarcomeres manifests as a series of bands visible along the muscle fibers, which is responsible for the striated appearance observed in microscopic images of this tissue. There are two types of striated muscle:
Muscle contraction is the activation of tension-generating sites within muscle cells. In physiology, muscle contraction does not necessarily mean muscle shortening because muscle tension can be produced without changes in muscle length, such as when holding something heavy in the same position. The termination of muscle contraction is followed by muscle relaxation, which is a return of the muscle fibers to their low tension-generating state.
Myofilaments are the three protein filaments of myofibrils in muscle cells. The main proteins involved are myosin, actin, and titin. Myosin and actin are the contractile proteins and titin is an elastic protein. The myofilaments act together in muscle contraction, and in order of size are a thick one of mostly myosin, a thin one of mostly actin, and a very thin one of mostly titin.
Vancouver General Hospital is a medical facility located in Vancouver, British Columbia. It is the largest facility in the Vancouver Hospital and Health Sciences Centre (VHHSC) group of medical facilities. VGH is Canada's third largest hospital by bed count, after Hamilton General Hospital, and Foothills Medical Centre.
Vancouver Hospital and Health Sciences Centre (VHHSC) is an acute care hospital affiliated with the University of British Columbia and located in Vancouver, British Columbia. The VHHSC is the second largest hospital in Canada, with 1,900 beds and nearly 116,000 patients each year. VHHSC employs 9500 staff and utilizes 1000 volunteers. As of 2005, the hospital's annual budget is $463 million. It is managed by Vancouver Coastal Health.
Troponin T is a part of the troponin complex, which are proteins integral to the contraction of skeletal and heart muscles. They are expressed in skeletal and cardiac myocytes. Troponin T binds to tropomyosin and helps position it on actin, and together with the rest of the troponin complex, modulates contraction of striated muscle. The cardiac subtype of troponin T is especially useful in the laboratory diagnosis of heart attack because it is released into the blood-stream when damage to heart muscle occurs. It was discovered by the German physician Hugo A. Katus at the University of Heidelberg, who also developed the troponin T assay.
Troponin I is a cardiac and skeletal muscle protein family. It is a part of the troponin protein complex, where it binds to actin in thin myofilaments to hold the actin-tropomyosin complex in place. Troponin I prevents myosin from binding to actin in relaxed muscle. When calcium binds to the troponin C, it causes conformational changes which lead to dislocation of troponin I. Afterwards, tropomyosin leaves the binding site for myosin on actin leading to contraction of muscle. The letter I is given due to its inhibitory character. It is a useful marker in the laboratory diagnosis of heart attack. It occurs in different plasma concentration but the same circumstances as troponin T - either test can be performed for confirmation of cardiac muscle damage and laboratories usually offer one test or the other.
Cardiac muscle troponin T (cTnT) is a protein that in humans is encoded by the TNNT2 gene. Cardiac TnT is the tropomyosin-binding subunit of the troponin complex, which is located on the thin filament of striated muscles and regulates muscle contraction in response to alterations in intracellular calcium ion concentration.
Troponin C, also known as TN-C or TnC, is a protein that resides in the troponin complex on actin thin filaments of striated muscle and is responsible for binding calcium to activate muscle contraction. Troponin C is encoded by the TNNC1 gene in humans for both cardiac and slow skeletal muscle.
β-Tropomyosin, also known as tropomyosin beta chain is a protein that in humans is encoded by the TPM2 gene. β-tropomyosin is striated muscle-specific coiled coil dimer that functions to stabilize actin filaments and regulate muscle contraction.
Troponin I, fast skeletal muscle is a protein that in humans is encoded by the TNNI2 gene.
Fast skeletal muscle troponin T (fTnT) is a protein that in humans is encoded by the TNNT3 gene.
Samuel Victor Perry FRS was an English biochemist who was a pioneer in the field of muscle biochemistry. In his earlier years he was a rugby union lock who played club rugby for Southport R.F.C., Cambridge University R.U.F.C. and international rugby for England.
Clara Franzini-Armstrong is an Italian-born American electron microscopist, and Professor Emeritus of Cell and Developmental Biology at University of Pennsylvania.
David A. Hood is a Canadian exercise physiologist and Director of the Muscle Health Research Centre at York University, Toronto, Canada. He is a professor and holder of an NSERC Tier I Canada Research Chair in Cell Physiology. Hood is credited with making significant research advances in understanding of the biology of exercise, mitochondria and muscle health.
