Chapter 30

A human's internal organs are protected mainly by the a. hydrostatic skeleton. b. axial skeleton. c. exoskeleton. d. appendicular skeleton

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. asalmon b. asnake c. a sparrow d. 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

What is the role of calcium in muscle contraction? a. Its binding to a regulatory protein causes the protein to move, exposing act in 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?

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.

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?

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

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.