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Smooth muscle is grouped into two types: single-unit smooth muscle, also known as visceral smooth muscle, and multiunit smooth muscle. Most smooth muscle is of the single-unit type, and is found in the walls of most internal organs (viscera); and lines blood vessels (except large elastic arteries), the urinary tract , and the digestive tract .
Agonism of beta-2 receptors causes vasodilation and low blood pressure (i.e. the effect is opposite of the one resulting from activation of alpha-1 and alpha-2 receptors in the vascular smooth muscle cells). Usage of beta-2 receptor agonists as hypotensive agents is less widespread due to adverse effects such as unnecessary bronchodilation in ...
Named for their lighter appearance under a polarization microscope. H-band is the zone of the thick filaments that has no actin. Within the H-zone is a thin M-line (from the German "mittel" meaning middle ), appears in the middle of the sarcomere formed of cross-connecting elements of the cytoskeleton.
Smooth muscle tissue is mostly made of actin and myosin, [3] two proteins that interact together to produce muscle contraction and relaxation. Myosin II, also known as conventional myosin, has two heavy chains that consist of the head and tail domains and four light chains (two per head) that bind to the heavy chains in the “neck” region.
A study of the developing leg muscle in a 12-day chick embryo using electron microscopy proposes a mechanism for the development of myofibrils. Developing muscle cells contain thick (myosin) filaments that are 160–170 Å in diameter and thin (actin)filaments that are 60–70 Å in diameter. Young myofibres contain a 7:1 ratio of thin to thick ...
This shape change causes the cytosolic side of the pump to open, allowing the two Ca 2+ to enter. The cytosolic side of the pump then closes and the sarcoplasmic reticulum side opens, releasing the Ca 2+ into the SR. [6] A protein found in cardiac muscle, called phospholamban (PLB) has been shown to prevent SERCA from working. It does this by ...
[3] [4] The Bayliss effect in vascular smooth muscles cells is a response to stretch. This is especially relevant in arterioles of the body. When blood pressure is increased in the blood vessels and the blood vessels distend, they react with a constriction; this is the Bayliss effect. Stretch of the muscle membrane opens a stretch-activated ion ...
Mural cells were described for the first time in the late 19th century as contractile cells lining up around the endothelium. In reality, it was a variety of cells that had been observed and bundled up under the common name of Rouget cells. Later studies brought controversy about their contractility, and this remains an elusive point today. [4]