47. Muscle Systems

What type of muscle is striated with intercalated disks?

Which statement about muscle contraction is correct?

What do all muscle tissues have in common?

Why is having a hydrostatic skeleton rather than an internal skeleton advantageous to an earthworm?

Locomotion requires that an animal expend energy to overcome __________.

When comparing the different styles and adaptations of each major type of locomotion, what is the most energy-efficient mode of locomotion?

Complete this concept map on animal movement.

Arm muscles and leg muscles are arranged in antagonistic pairs. How does this affect their functioning? a. It provides a backup if one of the muscles is injured. b. One muscle of the pair pushes while the other pulls. c. A single motor neuron can control both of them. d. It allows the muscles to produce opposing movements.

Gravity would have the least effect on the movement of which of the following? (Explain your answer.) a. a salmon a. a snake a. a sparrow a. a grasshopper

Which of the following bones in the human arm corresponds to the femur in the leg? a. radius b. tibia c. humerus d. metacarpal

Which of the following animals is correctly matched with its type of skeleton? a. fly—endoskeleton b. earthworm—exoskeleton c. lobster—exoskeleton d. bee—hydrostatic skeleton

When a dog is running fast, its body position is stabilized by a. side-to-side undulation. b. energy stored in tendons. c. foot contact with the ground. d. its momentum.

What is the role of calcium in muscle contraction? a. Its binding to a regulatory protein causes the protein to move, exposing actin binding sites to the myosin heads. b. It provides energy for contraction. c. It blocks contraction when the muscle relaxes. d. It forms the heads of the myosin molecules in the thick filaments inside a muscle fiber.

Muscle A and muscle B have the same number of fibers, but muscle A is capable of more precise control than muscle B. Which of the following is likely to be true of muscle A? (Explain your answer.) a. It is controlled by more neurons than muscle B. b. It contains fewer motor units than muscle B. c. It is controlled by fewer neurons than muscle B. d. It has larger sarcomeres than muscle B.

Which of the following statements about skeletons is true? a. Chitin is a major component of vertebrate skeletons. b. Loss of forelimbs in snakes involved little change in the axial skeleton. c. Most cnidarians must shed their skeleton periodically to grow. d. Vertebrate bones contain living cells.

In terms of both numbers of species and numbers of individuals, insects are the most successful land animals. Write a paragraph explaining how their exoskeletons help them live on land. Are there any disadvantages to having an exoskeleton?

Distance runner Paula Radcliffe has won dozens of long-distance races and held the women's world record for the marathon since 2003. Scientists, trainers, and athletes alike have wondered about the extent to which muscle structure and function contribute to success in athletes such as Radcliffe. What makes elite distance runners so good? Are their muscles somehow different from those of less successful athletes and non-athletes? Compare and contrast the structure and function of the three types of skeletal muscle fibers.

An owl swoops down, seizes a mouse in its talons, and flies back to its perch. Explain how its wings enable it to overcome the downward pull of gravity as it flies upward.

Distance runner Paula Radcliffe has won dozens of long-distance races and held the women's world record for the marathon since 2003. Scientists, trainers, and athletes alike have wondered about the extent to which muscle structure and function contribute to success in athletes such as Radcliffe. What makes elite distance runners so good? Are their muscles somehow different from those of less successful athletes and non-athletes? Predict who would likely have a greater proportion of fast glycolytic fibers in their gastrocnemius (calf) muscle—an elite distance runner or an elite sprinter. Explain.

The greatest concentration of thoroughbred horse farms is in the bluegrass region of Kentucky. The grass in the limestone-based soil of this area is especially rich in calcium. How does this grass affect the development of championship horses?

Distance runner Paula Radcliffe has won dozens of long-distance races and held the women's world record for the marathon since 2003. Scientists, trainers, and athletes alike have wondered about the extent to which muscle structure and function contribute to success in athletes such as Radcliffe. What makes elite distance runners so good? Are their muscles somehow different from those of less successful athletes and non-athletes? Predict the effect of training for a marathon on the number of muscle cells in the gastrocnemius. Explain.

Describe how you bend your arm, starting with action potentials and ending with the contraction of a muscle. How does a strong contraction differ from a weak one?

Distance runner Paula Radcliffe has won dozens of long-distance races and held the women's world record for the marathon since 2003. Scientists, trainers, and athletes alike have wondered about the extent to which muscle structure and function contribute to success in athletes such as Radcliffe. What makes elite distance runners so good? Are their muscles somehow different from those of less successful athletes and non-athletes? To discover the relationship between muscle-fiber types and performance, researchers obtained tiny biopsies of the gastrocnemius of 14 elite distance runners, 18 trained but non-elite distance runners, and 19 untrained subjects. They categorized the fiber types as slow or fast. (At the time of the study, intermediate fibers had not been identified as a third type.) Some of their data are shown here (* means). What conclusions can you draw from these data?

Using examples, explain this statement: 'Vertebrate skeletons are variations on a theme.'

Distance runner Paula Radcliffe has won dozens of long-distance races and held the women's world record for the marathon since 2003. Scientists, trainers, and athletes alike have wondered about the extent to which muscle structure and function contribute to success in athletes such as Radcliffe. What makes elite distance runners so good? Are their muscles somehow different from those of less successful athletes and non-athletes? The researchers looked more closely at the data within the group of elite runners. Although the mean proportion of slow fibers was 79 percent in this group, individual values ranged from 27 percent in one runner to 98 percent in another. How does this finding affect your interpretation of the relationship between athletic performance and muscle-fiber types?

Drugs are often used to relax muscles during surgery. Which of the following chemicals do you think would make a better muscle relaxant, and why? Chemical A: Blocks acetylcholine receptors on muscle cells. Chemical B: Floods the cytoplasm of muscle cells with calcium ions.

Distance runner Paula Radcliffe has won dozens of long-distance races and held the women's world record for the marathon since 2003. Scientists, trainers, and athletes alike have wondered about the extent to which muscle structure and function contribute to success in athletes such as Radcliffe. What makes elite distance runners so good? Are their muscles somehow different from those of less successful athletes and non-athletes? Imagine that Paula Radcliffe is racing against a bird and a fish, each with the same mass as Paula. Which organism would have the highest cost of locomotion during the race?

An earthworm's body consists of a number of fluid-filled compartments, each with its own set of longitudinal and circular muscles. But in the roundworm, a single fluid-filled cavity occupies the body, and there are only longitudinal muscles that run its entire length. Predict how the movement of a roundworm would differ from the movement of an earthworm.

When a person dies, muscles become rigid and fixed in position—a condition known as rigor. Rigor mortis occurs because muscle cells are no longer supplied with ATP (when breathing stops, ATP synthesis ceases). Calcium also flows freely into dying cells. The rigor eventually disappears because the biological molecules break down. Explain, in terms of the mechanism of contraction described in Modules 30.9 and 30.10, why the presence of calcium and the lack of ATP would cause muscles to become rigid, rather than limp, soon after death.

SCIENTIFIC THINKING Imagine you have a friend who had her child's ACTN3 genotype tested. After reviewing the study described in Module 30.12, what cautions would you offer about interpreting the test results?