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Reading Notes Section 10.1 Pages 331-342 ■ ____________ muscle cells are non-striated, have a __________ nucleus, and are usually arranged in _____________ lines, forming sheets. They are under ________________ control and found in the walls of many _______________ organs. ■ Cardiac muscle is _____________ found in the ______________ and forms the wall of this organ. Its cells are ______________, and each has a single ______________. Cardiac muscle cells are _____________ and branched, forming a ______________, net-like structure. Cardiac muscle contraction is ________________. ■ _____________ muscles are tubular and striated. Skeletal muscle contraction is ___________________. These muscle cells are __________, and each has a number of ______________ (multinucleated). They are usually referred to as ______________, rather than ______________. To lengthen, a muscle must ____________ so that an opposing force can ___________ the muscle back to its full length. The arrangement of _______________ pairs of muscles around a joint (in effect, a fulcrum) allows them to act together to _______________ each other out and provides the force to move a ______________ (in effect, a lever) in _________________ directions. ________________ muscle fibre consists of hundreds of thousands of cylindrical sub-units called _________________. Each of these is made of even finer _____________________, which contain _______________ structures responsible for muscle contraction. An _______________ (thin) myofilament consists of two strands of protein molecules that are wrapped around each other, somewhat like two strands of _____________ loosely wound together. A myosin (______________) myofilament is also composed of two strands of ______________ wound around each other; however, a myosin myofilament is about 10 times ______________ than an actin myofilament, and the myosin strands have a different shape. One end of a myosin myofilament consists of a long ____________, while the other end consists of a _________________-headed globular region, often called the “____________________.” When a muscle fibre ______________, the heads of thousands of myosin myofilaments move _____________. This moves them closer to their rod-like “backbone” and a few nanometers in the direction of the __________. Because the heads are _____________ (chemically bound) at this time to actin myofilaments, the ____________ myofilaments are pulled along with the myosin heads as they flex. As a result, the actin myofilaments _____________ past the myosin myofilaments in the direction of the flex. As one myosin ______________ after another flexes, the myosin, in effect, “walks” in place, step by step, along the _______________. Each step requires a molecule of ____________ to provide the energy that repositions the _________________ head before each flex. The ______________________ model of muscle contraction can be described as follows: ■ Within each myofilament, the _______________ is anchored at one end, at a position in striated muscle tissue called the ____________ line. Because it is tethered like this, the movement of actin pulls its “_______________” (the Z line) along with it. ■ As _____________ moves past ______________, it drags the Z line toward the _________________. ■ The mechanism of muscle contraction depends on the structural arrangement of __________________ of myosin myofilaments in relation to thousands of pairs actin myofilaments. With one actin molecule being pulled __________________ in one direction, and the other actin molecule being pulled inward in the _________________ direction, the two __________ of actin drag the ______________ lines towards each other as they slide past the ________________. As the Z lines are pulled _______________ together, the plasma membranes to which they are attached move __________________ one another, and the entire muscle fibre __________________. Muscle cannot contract without ____________ ions. When the ________________ ion concentration in the sarcoplasm is low, ________________ inhibits myosin binding, and the muscle is ________________. When the calcium ion concentration is _____________, Ca++ binds to _______________. This causes the troponintropomyosin complex to be shifted away from the attachment sites for the ____________ heads on the _________________. When this repositioning has occurred, the myosin heads attach to actin and, using ATP energy, move the actin myofilament to shorten the myofibril. __________________ is a high-energy compound that builds up when a muscle is resting. This compound cannot participate directly in muscle contraction; instead, it can regenerate ______________. The chemical reaction occurs in the midst of sliding filaments. Therefore, it is the ________________ way to make ATP available to muscles. Creatine phosphate provides enough _____________ for only about ________________ seconds of intense activity, and then it is spent. ___________________, such as creatine phosphate breakdown, supplies ATP without consuming _________________. This allows the muscle to continue activity in ________________ conditions. Aerobic cellular respiration, completed in ___________________, usually provides most of a muscle’s ___________. ________________ and ___________ are stored in muscle cells. Therefore, a muscle fibre can use ______________ from glycogen and fatty acids from fats as fuel to produce _____________ when oxygen is available. When a muscle uses fermentation to supply its energy needs, it incurs an oxygen _______________. _______________ is obvious when a person continues to breathe heavily after exercising. Replenishing an oxygen deficit requires replenishing _______________________ supplies and disposes of _________________. Lactate can be changed back to ________________ and metabolized completely in mitochondria; it can also be sent to the liver to synthesize glycogen.