power tions) the one alternative that best completes the statement or answers th

Question

power tions) the one alternative that best completes the statement or answers the question 1) of str 1) Each skeletal muscle fiber contains myofibrils ) 50 to 100 B) 100 to 150 C) 150 to 200 D) 200 to 500 E) hundreds to thousands group the fi grou 2) 2) Which of the following statements is (are) true regarding human muscles? A) Slow fibers are abundant in the calf muscles B) Most have both sow and fast fibers C) Eye museles are composed entirely of fast fibers. D) Slow fibers are abundant in the back muscles E) All of the above. the t dipl Fig indi 3) 3) During activities requiring aerobic endurance A) oxygen is not required B) fatigue occurs in a few minutes Q) glycogen and glycolysis are the primary sources of reerve energy D) oxygen debts are common. E) most of the musc le's energy is produced in mitochondria, 4) 4) Which of the following is not characteristic of smooth muscle? A) Neurons that innervate smooth muscles are under involuntary control B) The thin filaments of smooth muscle fibers are attached to dense bodies. C) Smooth muscles do not contain sarcomeres. D) Smooth muscles are uninucleate. E) Smooth muscle connective tissue forms tendons and aponeuroses 5) 5) At peak levels of muscle exertion the mitochondria can supply A) only about one-third of the energy required by the muscle B) all of the energy required by the muscle. C) only about 10 percent of the energy required by the muscle. D) 80 percent of the energy required by the muscle. E) more than half of the energy required by the muscle. 6) When a skeletal muscle fiber contracts, 6) A) the zones of overlap get larger. B) the width of the A band remains constant C) the H bands and I bands get smaller D) the Z lines get closer together. E) all of the above

Explanation / Answer

1. Myofibril is the basic rod like unit of muscle cells.These are composed of proteins like actin and myosin.These are organized in filaments called as myofilaments.The filaments are organized in repeating subunits along the length of myofibrils.These subunits are called sarcomeres.So generally there are 50-100 myofibrils in each skeletal muscle fiber.

2. Slow fibers contain more number of mitrochondria hence can produce more energy during contraction. Slow fibers are less dependent on anerobic metabolism than the fast fibers.

3. During most of the aerobic processes the most of the muscle's energy is produced in mitrochondria via Kreb's cycle that is considered to be aerobic while the glycolysis is independent of oxygen.

4. Smooth muscle connective tissue forms tendons and aponeurosis

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