Chapter 12 Muscles

________ is composed of multiple globular molecules polymerized to form long chains or filaments A) Actin B) Tropomyosin C) Troponin D) Myosin E) Titin

A) Actin

As ATP binds to the myosin head at the beginning of a muscle contraction cycle, the myosin head immediately A) detaches from actin B) initiates binding with actin. C) tightens its bond to actin. D) swivels

A) detaches from actin

The origin is the end of the skeletal muscle that attaches to the A) more stationary bone. B) more mobile bone. C) tendon. D) ligament

A) more stationary bone

The function of the titin protein is to A) stabilize the position of the contractile filaments. B) pull Z lines together during contraction. C) interact with actin during contraction. D) release calcium during contraction. E) cover the myosin binding site on the actin molecule

A) stabilize the position of the contractile filaments.

The H zone contains A) thick filaments. B) thin filaments only. C) actin only. D) thick and thin filaments

A) thick filaments

Most of the time, the parallel thick and thin filaments of the myofibrils are connected by ________ that span the space between myosin and actin molecules. A) tropomyosin molecules B) crossbridges C) nebulin molecules D) sarcomeres E) calcium ions

B) crossbridges

The function of transverse tubules is to A) store Ca2+ ions inside the muscle fiber. B) rapidly conduct action potentials to the interior of the muscle fiber. C) ensure a supply of glycogen throughout the muscle sarcoplasm. D) conduct ATP molecules out of the mitochondria throughout the sarcoplasm

B) rapidly conduct action potentials to the interior of the muscle fiber.

For antagonistic muscle groups to move a limb, flexor contraction occurs coincident with A) contraction of the extensor. B) relaxation of the extensor. C) no changes in the extensor. D) contraction of the tendon

B) relaxation of the extensor

The I band contains A) thick filaments only. B) thin filaments only. C) myosin only. D) thick and thin filaments

B) thin filaments only

A flexor is a skeletal muscle whose shortening moves attached bones A) away from one another. B) towards one another. C) medially. D) laterally.

B) towards one another

When a skeletal muscle cell contracts and the muscle shortens, A) myosin heads generate a single power stroke. B) the position of an actin molecule relative to a myosin molecule does not change. C) some myosin heads are forming crossbridges as others are releasing them. D) the actin ATPase allows the actin molecule to swivel. E) the actin molecule swivels during the power stroke

C) some myosin heads are forming crossbridges as others are releasing them

Skeletal muscle cells are usually attached to bone by A) fascicles. B) ligaments. C) tendons. D) flexors

C) tendons

8) Striated muscles are so-called because of a repeating pattern of light and dark bands. One repeating unit of the banding pattern is called a A) myofilament. B) myomere. C) sarcofibril. D) sarcomere. E) crossbridge

D) sarcomere.

When a skeletal muscle generates enough force during contraction to shorten, A) only the sarcomere will shorten. B) only the A band will shorten. C) only the I band will shorten. D) the sarcomere and the I band will shorten. E) the sarcomere, the A band, and the I band will shorten

D) the sarcomere and the I band will shorten

The molecular event that occurs immediately after the power stroke is the A) release of actin from the myosin head. B) hydrolysis of ATP by the myosin head. C) release of ADP from the myosin. D) binding of tropomyosin to the myosin. E) binding of actin to the myosin.

The hydrolysis of ATP causes myosin to immediately A) swivel, moving the actin molecule. B) release ADP. C) release from the actin. D) rotate into a position (cocked) to bind to actin. E) bind more tightly to the actin (rigor) C) release of ADP from the myosin.

The tension generated in a skeletal muscle fiber is directly proportional to the number of A) thick and thin filaments present. B) nebulin and titin molecules present. C) high-energy crossbridges formed. D) low-energy crossbridges formed. E) active sarcomeres

C) high-energy crossbridges formed

Each myosin head has a binding site for A) calcium only. B) actin only. C) ATP only. D) calcium and ATP. E) actin and ATP

E) actin and ATP

In order for high force crossbridges to form in contracting skeletal muscle, calcium must A) bind to calmodulin to phosphorylate the myosin. B) phosphorylate the tropomyosin which moves it. C) phosphorylate the troponin to move the tropomyosin. D) bind to tropomyosin which moves the troponin. E) bind to troponin which moves the tropomyosin

E) bind to troponin which moves the tropomyosin