Chapter 10

What type of contraction requires the greatest amount of tension? a. isotonic eccentric contraction b. isometric contraction c. isotonic concentric contraction d. miometric contraction

a.

Choose the correct sequence of events that occur in preparation for contraction a.Action potential arrives at triad, calcium is released from the terminal cisternae, calcium binds to troponin, tropomyosin exposes the actin active sites b.Tropomyosin exposes the actin active sites, calcium binds to troponin, action potential arrives at triad, calcium is released from the terminal cisternae c.Calcium is released from the terminal cisternae, calcium binds to troponin, action potential arrives at triad, tropomyosin exposes the actin active sites d.Calcium binds to troponin, action potential arrives at triad, calcium is released from the terminal cisternae, tropomyosin exposes the actin active sites

a. Action potential arrives at triad, calcium is released from the terminal cisternae, calcium binds to troponin, tropomyosin exposes the actin active sites

Which statement best describes the function of myoglobin? a. Myoglobin stores oxygen in muscle cells. b. Myoglobin is a source of ATP for muscles. c. Myoglobin hydrolyzes ATP. d. Myoglobin catabolizes glycogen.

a. Myoglobin stores oxygen in muscle cells.

The binding of ATP to myosin is responsible for a.Release of the myosin heads from the actin active sites b.Recocking of the myosin heads c.The power stroke d.The movement of tropomyosin, exposing the actin active sites

a. Release of the myosin heads from the actin active sites

During muscle fiber relaxation, calcium channels in the SR close because a.The resting membrane potential is restored b.Calcium levels in the SR are depleted c.Calcium is released from the SR Calcium is pumped into the extracellular fluid

a. The resting membrane potential is restored

Which of the following statements is the most accurate description of the sliding filament mechanism? a. Thin filaments slide past thick filaments towards the M line. b. Both thick and thin filaments shorten. c. Thick filaments shorten while thin filaments remain unchanged. d. Z discs slide over the thick and thin filaments.

a. Thin filaments slide past thick filaments towards the M line.

In response to physical inactivity, we expect to see muscles: a. atrophy. b. increase numbers of myofibrils. c. hypertrophy. d. increase the diameter of the muscle fiber.

a. atrophy

Tropomyosin a.Covers actin active sites b.Binds calcium ions c.Is a small, globular protein d.Has three subunits

a. covers actin active sites

The binding of a myosin head to an actin molecule is termed a: a. crossbridge. b. power stroke. c. synaptic cleft. d. triad.

a. crossbridge

Once excitation-contraction coupling has occurred, calcium ion concentration increases dramatically in the: a. cytosol of the muscle fiber. b. terminal cisterna. c. sarcolemma. d. sarcoplasmic reticulum.

a. cytosol of the muscle fiber.

When an action potential arrives in an axon terminal, synaptic vesicles containing acetylcholine are released by: a. exocytosis. b. osmosis. c. facilitated diffusion. d. endocytosis.

a. exocytosis

A pathway of ATP production that results in the formation of lactic acid is: a. glycolytic catabolism. b. anabolism. c. oxidative catabolism. d. catabolism.

a. glycolytic catabolism.

The sodium channels of the motor end plate are a.Ligand-gated channels b.Voltage-gated channels c.Na+/K+ pumps d.Mechanically gated channels

a. ligand-gated channels

Where are receptors for acetylcholine located? a. motor end plate b. axon terminal c. triad d. sarcomere

a. motor end plate

Between the start of the latent period and the start of the contraction period, there is a time interval during which the muscle cannot respond to another stimulus. This brief period is known as the: a. refractory period. b. relaxation period. c. tension period. d. action potential.

a. refractory period.

What does the depolarization of the transverse tubules (T-tubules) promote? a. release of calcium from the sarcoplasmic reticulum b. binding of acetylcholine to ligand-gated sodium ion channels c. release of acetylcholine from vesicles in the motor neuron into the synaptic cleft d. entry of sodium ions into the muscle fiber through voltage-gated sodium ion channels

a. release of calcium from the sarcoplasmic reticulum

The Na+/K+ pump helps a muscle cell maintain a state of: a. resting membrane potential. b. propagation. c. action potential. d. depolarization.

a. resting membrane potential.

The storage and release of calcium ions is the key function of the: a. sarcoplasmic reticulum. b. sarcolemma. c. sarcoplasm. d. mitochondrion.

a. sarcoplasmic reticulum.

Type I fibers lack: a. speed. b. a blood supply. c. myoglobin. d. mitochondria.

a. speed

A triad consists of a.Two terminal cisternae and a T-tubule b.An M line and two zones of overlap c.Two T-tubules and a terminal cisterna d.A zone of overlap and two M lines

a. two terminal cisternae and a T-tubule

Place the following events of excitation in the correct order. 1.ion channels on the sarcolemma open and sodium ions enter the muscle fiber 2.the entry of sodium ions into the muscle fiber depolarizes the sarcolemma locally 3.acetylcholine is released from vesicles in the motor neuron into the synaptic cleft 4.an action potential arrives at the axon terminal of a motor neuron 5.acetylcholine binds to ligand-gated sodium ion channels in the motor end plate a. 3, 4, 5, 1, 2 b. 4, 3, 5, 1, 2 c. 2, 4, 3, 5, 1 d. 4, 5, 3, 2, 1

b. 4,3,5,1,2

During muscle fiber relaxation a.Calcium levels in the sarcoplasm rise b.Calcium is pumped back into the SR c.Calcium is released from the SR d.Calcium is pumped into the extracellular fluid

b. Calcium is pumped back into the SR

Sarcolemma repolarization during relaxation a.Means that the interior of the cell becomes less negative b.Restores the resting membrane potential c.Only occurs at the motor end plate of the fiber d.Is caused by closure of calcium channels

b. Restores the resting membrane potential

What is accomplished by the power stroke? a. The power stroke cocks the myosin head into its high-energy position. b. The power stroke results in myosin heads pulling actin toward the center of the sarcomere. c. The power stroke allows the myosin heads to bind to actin. d. The power stroke causes the myosin and actin filaments to shorten and contract.

b. The power stroke results in myosin heads pulling actin toward the center of the sarcomere.

Which of the following wraps and surrounds an individual skeletal muscle fiber? a. sarcoplasmic reticulum b. endomysium c. epimysium d. perimysium

b. endomysium

A pathway of ATP production that results in the formation of lactic acid is: a. oxidative catabolism. b. glycolytic catabolism. c. anabolism. d. aerobic catabolism.

b. glycolytic catabolism.

A single motor neuron together with all the skeletal muscle fibers it innervates is called a: a. synaptic cleft. b. motor unit. c. neuromuscular junction. d. motor end plate.

b. motor unit.

Troponin has three subunits. Which of the following does NOT bind to one of these subunits? a.Actin b.Myosin c.Calcium d.Tropomyosin

b. myosin

Through which ATP-generating mechanism can long-lasting muscle contractions be sustained? a. glycolysis b. oxidative catabolism c. creatine phosphate reaction d. anaerobic catabolism

b. oxidative catabolism

Hydrolysis of ATP is responsible for a.Release of the myosin heads from the actin active sites b.Recocking of the myosin heads c.The power stroke d.The movement of tropomyosin, exposing the actin active sites

b. recocking of the myosin heads

Jorge tried to pick up his sofa but discover that it is much heavier than he expected. What must occur in the muscle to increase tension so he can pick up this heavy piece of furniture? a. tetanic spasm b. recruitment of additional motor units c. pliometric contraction d. isotonic eccentric contractions

b. recruitment of additional motor units

What is the functional contractile unit of the myofibril where muscle tension is produced? a. I band b. sarcomere c. sarcolemma d. A band

b. sarcomere

The end plate potential is generated by the influx of _______ into the motor end plate. a.calcium b.sodium c.potassium d. chloride

b. sodium

Deep inward extensions of the sarcolemma form a tunnel-like network inside the muscle cell known as: a. the sarcoplasmic reticulum. b. transverse tubules (T-tubules). c. myofilaments. d. myofibrils.

b. transverse tubules (T-tubules).

The channels that open in the sarcolemma surrounding the motor endplate and generate an action potential are a.Ligand-gated channels b.Voltage-gated channels c.Na+/K+ pumps d.Mechanically gated channels

b. voltage-gated channels

What characteristic is NOT descriptive of cardiac muscle tissue? a. located in the heart b. voluntary muscle contractions c. intercalated discs d. striations

b. voluntary muscle contractions

What value best represents resting membrane potential of skeletal muscle cells? a. +35 mV b. +15 mV c. −90 mV d. 0 mV

c. -90 mV

Latrotoxin, produced by the poisonous black widow spider, increases the release of acetylcholine. How do muscle cells respond? a. Muscle cells will twitch irregularly when excess acetylcholine exists. b. Muscle cells will experience a longer latent period when excess acetylcholine exists. c. Muscle cells will experience fused or complete tetanus when excess acetylcholine exists. d. Muscle cells will become paralyzed when excess acetylcholine exists.

c. Muscle cells will experience fused or complete tetanus when excess acetylcholine exists.

The end plate potential is a.An action potential b.A local repolarization c.A local depolarization d.A local hyperpolarization

c. a local depolarization

The main immediate source of ATP (lasting about 10 seconds) as muscle contractions begin comes from: a. fat. b. glycogen. c. creatine phosphate. d. glucose.

c. creatine phosphate

Which of the following promotes the depolarization stage? a. hydrolysis of ATP b. opening of voltage-gated potassium ion channels and potassium ions exit the cell c. opening of voltage-gated sodium ion channels and sodium ions enter the cell d. closure of voltage-gated sodium ion channels

c. opening of voltage-gated sodium ion channels and sodium ions enter the cell

A muscle cell experiencing resting membrane potential is: a. experiencing depolarization. b. propagating an action potential. c. polarized. d. more negatively charged on its exterior than in its interior.

c. polarized.

The term "synaptic cleft" refers to a.A fold on the motor end plate b.A vesicle in the synaptic terminus c.The gap between the neuron and the muscle fiber d.The space between adjacent muscle fibers

c. the gap btw the neuron and the muscle fiber

The release of ADP and Pi from myosin occurs during a.Release of the myosin heads from the actin active sites b.Recocking of the myosin heads c.The power stroke d.The movement of tropomyosin, exposing the actin active sites

c. the power stroke

The fastest muscle contraction would be produced by a: a. type IIx fiber. b. type III fiber. c. type IIa fiber. d. type I fiber.

c. type IIa fiber.

In order to trigger a muscle contraction, an action potential must reach the a.Sarcomeres b.Mitochondria c.Triads d.Nuclei

c.triads

Muscle contraction can occur when: a. I bands remain unchanged. b. A bands lengthen. c. myosin filaments shorten. d. sarcomeres shorten.

d. sarcomeres shorten.

What are possible products of glycolytic, or anaerobic, catabolism? a. oxygen only b. glucose only c. creatine phosphate only d. ATP, pyruvate, and lactic acid

d. ATP, pyruvate, and lactic acid

What do skeletal muscle tissue and cardiac muscle tissue share in common? a. Both skeletal and cardiac muscle tissues are voluntary. b. Both skeletal and cardiac muscle tissues perform peristalsis. c. Both skeletal and cardiac muscle tissues possess intercalated discs. d. Both skeletal and cardiac muscle tissues consist of striated muscle cells.

d. Both skeletal and cardiac muscle tissues consist of striated muscle cells.

-------is released from the SR in response to arrival of an action potential a. Na+ b. K+ c. Pi d. Ca++

d. Ca++

Acetylcholinesterase in the synaptic cleft degrades acetylcholine, allowing a.Depolarization of the motor end plate b.Calcium levels in the sarcoplasm to rise c.Tropomyosin to expose actin active sites d. Ligand-gated sodium channels to close

d. Ligand-gated sodium channels to close

Which aspect of muscle relaxation requires ATP? a.Motor end plate repolarization b.Blockage of actin active sites by tropomyosin c.Sarcomeres returning to their original length d.Pumping calcium ions back into the SR

d. Pumping calcium ions back into the SR

Which of the following is descriptive of skeletal muscle fibers? a. Skeletal muscle fibers are uninucleate. b. Skeletal muscle fibers are smaller than most cells. c. Skeletal muscle fibers lack a sarcolemma and myofibrils. d. Skeletal muscle fibers are striated.

d. Skeletal muscle fibers are striated.

What happens when troponin and tropomyosin block the active sites of actin? a. The muscle contraction increases tension. b. The muscle produces a weak contraction. c. The muscle contraction reaches peak tension. d. The muscle relaxes.

d. The muscle relaxes.

A triad consists of: a. actin filaments, troponin, and tropomyosin. b. a fascicle of skeletal muscle cells and its surrounding perimysium. c. myosin filaments, myosin heads, and myosin tails. d. a transverse tubule (T-tubule) and two terminal cisternae.

d. a transverse tubule (T-tubule) and two terminal cisternae.

During muscle contraction, myosin crossbridges bind to active sites on: a. troponin. b. T-tubules. c. tropomyosin. d. actin.

d. actin

Acetylcholine is released from the synaptic terminus in response to a.A ligand binding to a receptor on the synaptic terminus b.Sodium flowing into the synaptic terminus c.Potassium entering the synaptic terminus d.An action potential arriving at the synaptic terminus

d. an action potential arriving at the synaptic terminus.

What is required for excitation-contraction coupling? a. ATP only b. neither calcium ions nor ATP c. calcium ions only d. calcium ions and ATP

d. calcium ions and ATP

Where should most of the potassium ions be located when a muscle cell is at rest? a. transverse tubules (T-tubules) b. sarcoplasmic reticulum c. extracellular fluid d. cytosol of the muscle cell

d. cytosol of the muscle cell

The degree to which a muscle cell can stretch depends on its: a. excitability. b. contractility. c. conductivity. d. distensibility.

d. distensibility.

When muscle fibers are stimulated so frequently they do not have an opportunity to relax, they are experiencing: a. wave summation. b. unfused or incomplete tetanus. c. a twitch. d. fused or complete tetanus.

d. fused or complete tetanus.

What is the basic function of all muscle tissue? a. produce voluntary contractions b. stabilize joints c. regulate body temperature d. generate muscle tension

d. generate muscle tension

What is a necessary reactant for glycolytic, or anaerobic, catabolism to proceed? a. creatine phosphate b. oxygen c. myoglobin d. glucose

d. glucose

The type of contraction in which length of the muscle fibers do not change is called: a. tetany. b. isotonic eccentric. c. isotonic concentric. d. isometric.

d. isometric.

Resting muscles still have some degree of muscle tension produced by involuntary activation of motor units in the brain and spinal cord. This small amount of muscle tension is known as: a. recruitment. b. fused (complete) tetanus. c. isotonic contraction. d. muscle tone.

d. muscle tone

The synapse of a motor neuron with a muscle fiber is known as the: a. motor end plate. b. synaptic bulb. c. synaptic cleft. d. neuromuscular junction.

d. neuromuscular junction.

The power stroke a.Pulls the thick filaments toward the Z lines b.Positions the myosin heads in their high-energy position c.Shortens the length of the thin filaments d.Pulls the thin filaments toward the M lines

d. pulls the thin filaments towards the M lines.

The term "propagate" when referring to an action potential means a.Stimulate b.Inhibit c.Magnify d.Spread

d. spread