Ch. 7

A muscle ________ contains a sarcolemma, sarcoplasm, myofilaments, and myofibrils. A) fiber B) intercalated disc C) T-tubule D) myofibril E) motor end plate

A

Myofibrils are made primarily of A) actin and myosin. B) epimysium. C) ATP and ADP. D) troponin. E) tropomyosin.

A

The ________ contains vesicles filled with acetylcholine. A) axon terminal B) motor end plate C) neuromuscular junction D) synaptic cleft E) transverse tubule

A

The enzyme acetylcholinesterase causes acetylcholine to A) break down. B) synthesize. C) bond to actin. D) be secreted. E) form cross-bridges.

A

Neurotransmitters that cause skeletal muscle contraction are normally stored in A) myofibrils. B) motor neuron axon terminals. C) motor units. D) motor end plates. E) actin.

B

Skeletal muscle fibers differ from "typical cells" in that these muscle fibers A) lack a plasma membrane. B) have many nuclei. C) are very small. D) lack mitochondria. E) contain endoplasmic reticulum.

B

The active sites on actin molecules are usually covered up by other molecules. What is the critical material required to uncover the active sites on the actin molecules that will then bind to myosin heads? A) ATP B) calcium C) oxygen D) vitamin A E) titin

B

The area between Z lines is the A) sarcolemma. B) sarcomere. C) sarcoplasmic reticulum. D) myofibril. E) myofilament.

B

The specialized sarcolemma that contains acetylcholine receptors is the A) synaptic knob. B) motor end plate. C) motor unit. D) synaptic cleft. E) I band.

B

The terminal cisternae are structural features of the A) myofilaments. B) sarcoplasmic reticula. C) myofibrils. D) I bands. E) sarcolemma.

B

What is the function of the transverse tubule? A) the storage of calcium ions B) to transmit electrical impulses to the cell's interior C) to store sodium ions D) to allow cross-bridge attachment E) to produce myofibrils

B

Muscle fascicles are separated by A) endomysium. B) perimysium. C) epimysium. D) sarcolemma. E) periosteum.

B

A sheath of connective tissue surrounding a bundle of striated muscle fibers is called A) endomysium. B) perimysium. C) sarcolemma. D) epimysium. E) sarcoplasmic reticulum.

B

As a skeletal muscle contraction is initiated, acetylcholine binding alters the motor end plate membrane's permeability to A) acetylcholinesterase. B) sodium ions. C) calcium ions. D) chloride ions. E) potassium ions.

B

Each myofibril consists of approximately ________ sarcomeres. A) 10 B) 500 C) 10,000 D) 100,000 E) 2-3 million

C

The area of the sarcomere that is the light region between two successive A-bands is the A) Z line. B) M line. C) I band. D) myofibril. E) H band.

C

Tropomyosin strands are held in position by which of the following? A) actin molecules B) myosin molecules C) troponin molecules D) ATP molecules E) calcium ions

C

In response to action potentials arriving from the transverse tubules, the sarcoplasmic reticulum releases A) acetylcholine. B) sodium ions. C) potassium ions. D) calcium ions. E) acetylcholinesterase.

D

Upon the nerve impulse arriving at the axon terminal, A) active sites on actin are exposed. B) active sites on myosin are exposed. C) actin heads will bind to myosin. D) muscle relaxation occurs. E) acetylcholine is released.

E

Place these steps of muscle contraction in the correct order. 1. Action potential is generated along the sarcolemma 2. Nerve impulse arrives at synapse 3. Calcium is released into muscle cell cytoplasm 4. Acetylcholine is produced 5. Actin and myosin molecules continuously cross-link, with actin molecules being pulled inward A) 2, 3, 4, 1, 5 B) 4, 2, 1, 5, 3 C) 1, 2, 4, 3, 5 D) 2, 4, 1, 3, 5 E) 1, 2, 4, 5, 3

D

Regarding a skeletal muscle fiber, wherever a T-tubule encircles a myofibril, the tubule is tightly bound to A) the nucleus. B) the sarcolemma. C) the endomysium. D) the sarcoplasmic reticulum. E) thick filaments.

D

The region of a sarcomere containing myosin, going from one end of the myosin molecules to the other end of the myosin molecules, is the A) Z line. B) M line. C) H band. D) A band. E) I band.

D

The skeletal muscles store calcium ions in the terminal cisternae of the A) sarcolemma. B) sarcomere. C) sarcosome. D) sarcoplasmic reticulum. E) sarcoplasm.

D

The stiffness that occurs at death, when actin and myosin molecules stay linked to each other in a contracted state, is due to a lack of A) cAMP. B) DNA. C) RNA. D) ATP. E) tRNA.

D

The striated appearance of skeletal muscle results from A) the transverse tubule pattern. B) the sarcoplasmic reticulum. C) cisternae placement. D) actin and myosin arrangement. E) the perimysium arrangement.

D

Which of the following is one of the steps that ends a contraction? A) Sarcoplasmic reticulum absorbs sodium ions. B) Acetylcholine binds to receptors on the sarcolemma. C) Calcium ions bind to troponin. D) Acetylcholine is broken down by acetylcholinesterase. E) An action potential spreads across the entire surface of the muscle fiber.

D

A layer of collagen fibers that surrounds an entire muscle is called A) endomysium. B) perimysium. C) sarcolemma. D) sarcomere. E) epimysium.

E

Acetylcholinesterase is found within the A) nucleus. B) sarcolemma. C) myofibril. D) sarcomere. E) synaptic cleft.

E

After death, rigor mortis lasts until A) ATP is produced. B) T-tubules recapture calcium ions. C) sodium ions are released by the sarcoplasmic reticulum. D) sarcomeres lengthen. E) myofilaments are broken down.

E

Botulism A) is the result of an attack on acetylcholine receptors by the immune system. B) is usually tied to a genetic predisposition. C) is a viral illness. D) results from the loss of acetylcholine receptors at the motor end plate. E) results from a bacterial toxin that prevents the release of acetylcholine at the axon terminals.

E

Which of the following statements describes how muscles help maintain homeostasis? A) The contractions of skeletal muscles pull on tendons and move elements of the skeleton. B) Skeletal muscles are responsible for guarding the openings of the digestive and urinary tracts. C) Skeletal muscles are responsible for the pumping action of the heart. D) Skeletal muscles support the weight of some internal organs. E) Skeletal muscle contractions help maintain body temperature.

E

Which statement regarding skeletal muscle is true? A) Skeletal muscles are directly, but not indirectly, attached to bones. B) Skeletal muscles do not contain connective tissue. C) Skeletal muscles do not maintain body temperature. D) Skeletal muscles do not contain nervous tissue. E) Skeletal muscles contain blood vessels.

E