Smooth muscle is critically important to the function of the digestive system, reproductive system, respiratory system, vascular system (but not capillaries because their walls are composed of only a single layer of endothelial cells), urinary bladder, as well as many other organs. Test your basic knowledge of smooth muscle physiology by taking this simple quiz.
(1) In smooth muscle contraction, the majority of calcium (Ca2+) needed for contraction enters the cell from the extracellular fluid.
(2) In smooth muscle, when the cytoplasmic calcium (Ca2+) concentration is elevated, Ca2+ binds to this regulatory protein in order to initiate muscle contraction.
(3) Transverse (t) tubules are present in smooth muscle.
(4) Which one of the following is NOT true about smooth muscle?
(5) A single twitch of a smooth muscle cell can last: