Concept explainers
As Bolt s and Kimetto’s athletic feats attest, muscles can contract with amazing force. But sometimes they contract more than tendons can withstand. Achilles tendon injuries have sidelined a number of basketball stars including Kobe Bryant. Shaquille O'Neal, and Wesley Matthews as well as baseball star David Ortiz. Because tendons have a very limited Wood supply, recovery from a serious tear (tendon rupture) can take a full year, and elite athletes may never regain their former levels of performance. The Achilles tendon—the largest and strongest tendon in the body—attaches the calf muscles to the heel bone and is vulnerable to sudden muscle contractions, such as those that occur during running or jumping. This tendon flexes a hinge joint in the ankle. How do hinge joints work?
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Biology: Life on Earth with Physiology (11th Edition)
- After death, a person no longer makes ATP, so calcium stored in the sarcoplasmic reticulum diffuses down its concentration gradient into the muscle cytoplasm. This result is rigor mortis----an unbreakable state of muscle contraction that stiffens the body for a few days until muscles begin to decay. Explain why this contraction occurs.arrow_forwardFigure 38.37 Which of the following statements about muscle contraction is true? The power stroke occurs when ATP is hydrolyzed to ADP and phosphate. The power stroke occurs when ADP and phosphate dissociate from the myosin head. The power stroke occurs when ADP and phosphate dissociate from the actin active site. The power stroke occurs when Ca2+ binds the calcium head.arrow_forwardSkeletal muscle contraction requires _________. a. calcium ions b. ATP c. arrival of a nerve impulse d. all of the abovearrow_forward
- The _____ is the basic unit of muscle contraction. a. myofibril b. sarcomere c. muscle fiber d. myosin filamentarrow_forwardYou are training athletes for the 100-meter dash. They need muscles specialized for speed and strength, not endurance. What muscle characteristics would your training regimen aim to develop? How would you alter it to train a long-distance swimmer?arrow_forwardWhy do you think a person is able to perform anaerobic exercise (such as lifting and holding a heavy weight) only briefly but can sustain aerobic exercise (such as walking or swimming) for long periods? (Hint: Muscles have limited energy stores.)arrow_forward
- Nerve impulses first stimulate a skeletal muscle fiber at _______. a. T tubules b. sarcomeres c. neuromuscular junctions d. actin binding sitesarrow_forwardWhich arrangement best describes a bipennate muscle? The muscle fibers feed in on an angle to a long tendon from both sides. The muscle fibers feed in on an angle to a long tendon horn all directions. The muscle fibers feed in on an angle to a long tendon horn one side. The muscle fibers on one side of a tendon feed into it at a certain angle and muscle fibers on the other side of the tendon feed into it at the opposite angle.arrow_forwardA bursa ________. surrounds a tendon at the point where the tendon crosses a joint secretes the lubricating fluid for a synovial joint prevents friction between skin and bone, or a muscle tendon and bone is the strong band of connective tissue that holds bones together at a synovial jointarrow_forward
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