Chapter 9 : Skeletal Muscle Tissue Test

Aerobic metabolism normally provides ________ percent of the ATP demands of a resting muscle cell.

95

The region of the sarcomere containing the thick and thin filaments is the

A band

Which of the following motor units would produce the greatest tension? A.a motor unit in a back muscle B. a motor unit in a hand muscle C. a motor unit in an eye muscle

A. a motor unit in a back muscle

What physiological process occurs in the structure labeled "7"? ** A. conduction of the action potential into the cell interior B. the sliding filament theory C. activity of acetylcholinesterase D. release of protein into the muscle fiber E. release of neurotransmitter

A. conduction of the action potential into the cell anterior

The cytoplasm of the neuromuscular synaptic terminal contains vesicles filled with molecules of the neurotransmitter

Acetylcholene

When comparing slow motor units to fast motor units, slow units take about three times as long to reach peak tension. generate much less tension. are rich in the red protein myoglobin. have much smaller fiber diameters. All of the answers are correct.

All

Which of the following is a recognized function of skeletal muscle? A. produce movement B. guard body entrances and exits C. maintain posture D. maintain body temperature E. All of the answers are correct.

All answers are correct

During anaerobic glycolysis pyruvate is produced. oxygen is not consumed. ATP is produced. All of the answers are correct.

All of the answers are correct

Which of the following statements is/are true regarding human muscles? Which of the following statements is/are true regarding human muscles? Most have both slow and fast fibers. Slow fibers are abundant in the calf muscles. Slow fibers are abundant in the back muscles. Eye muscles are composed entirely of fast fibers. All of the answers are correct.

All of the answers are correct

Which of these would lead to increased oxygen consumption? increased muscle activity increased conversion of lactic acid to glucose increased heat production increased aerobic respiration by muscle cells All of the answers are correct.

All of the answers are correct.

Where are the myosin molecules located? ** A. 4 B. 5 C. 6 D. 7 E. 8

B. 5

Which of the following statements is not true about action potentials? A. They end in repolarization. B. They can travel in two directions. C. They can be generated in less than 2 msec. D.They can travel long distances within cells. E. They occur in neurons.

B. They can travel in two directions

Which of the following is greater? A. the concentration of calcium ion in the sarcoplasm of a resting muscle B. the concentration of calcium ion in the sarcoplasmic reticulum of a resting muscle

B. the concentration of calcium ion in the sarcoplasmic reticulum of a resting muscle

Which statement about excitation-contraction coupling is incorrect? Relaxation requires uptake of calcium ions by the sarcoplasmic reticulum. Calcium ion is released from the transverse tubule. Calcium ion is released from the sarcoplasmic reticulum. Troponin binds calcium ion and signals tropomyosin to move. Tropomyosin moves to expose myosin binding sites on actin

Calcium ion is released from the transverse tubule.

In response to action potentials arriving along the transverse tubules, the sarcoplasmic reticulum releases

Calcium ions

What is released from the structure labeled "9"? **

Calcium ions

Muscle tissue, one of the four basic tissue groups, consists chiefly of cells that are highly specialized for:

Contraction

Calcium ions are binding to troponin during the ________ of a muscle twitch.

Contraction phase

Muscular force can be adjusted to match different loads by A. varying the frequency of action potentials in motor neurons. B. recruiting more motor units. C. recruiting larger motor units. D. All of the answers are correct.

D. All of the answers are correct

Which of the following statements is incorrect? A. Skeletal muscle contractions help maintain body temperature. B. Skeletal muscles store nutrient reserves. C. Skeletal muscles support the weight of some internal organs. D. Skeletal muscles are responsible for the pumping action of the heart. E. The contractions of skeletal muscles pull on tendons and move bones of the skeleton.

D. Skeletal muscles are responsible for the pumping action of the heart.

During the ________ phase of action potential development, voltage-gated sodium channels are open.

Depolarization

Identify the structure where ATP is produced.** A. 7 B. 3 C. 2 D. 6 E. 1

E. 1

Where is ATP is consumed?** A. 1 B. 6 C. 3 D. 2 E. 3 and 6

E. 3 and 6

Where would calcium ions be predominately found? ** A. 1 B. 2 C. 4 D. 8 E. 9

E. 9

The thin filaments of striated muscle are made of which protein(s)? A. Tropomyosin B. Actin C. Troponin D. Nebulin E. All of the answers are correct.

E. All of the answers are correct

When a skeletal muscle fiber contracts: A. the zones of overlap get larger. B. the Z lines get closer together. C. the width of the A band remains constant. D. the H bands and I bands get smaller. E. All of the answers are correct.

E. All of the answers are correct

Which statement about the microscopic anatomy of skeletal muscle fibers is true? A. Each fiber has many nuclei. B. Cross striations result from the lateral alignment of thick and thin filaments. C. Muscle fibers are continuous from tendon to tendon. D. Tubular extensions of the sarcolemma penetrate the fiber transversely. E. All of the answers are true.

E. All of the answers are true.

Which of the following is an ion that is more concentrated inside the cell than outside? A. Calcium B. Chloride C. Hydrogen D. Sodium E. Potassium

E. Potassium

Which of the following best describes the sarcoplasmic reticulum? A. largely made of myosin molecules B. protein that accounts for elasticity of resting muscle C. repeating unit of striated myofibrils D. thin filaments are anchored here E. storage and release site for calcium ions

E. storage and release site for calcium ions

Which of the following is/are found in the structure labeled "3"? ** A. titin B. actin C.myosin D. tropomyosin E.All of the answers are correct

E.All answers are correct

Individual muscle cells are surrounded by what connective tissue?

Endomysium

The delicate connective tissue that surrounds the skeletal muscle fibers and ties adjacent muscle fibers together is the:

Endomysium

The dense layer of connective tissue that surrounds an entire skeletal muscle is the:

Epimysium

Synaptic vesicles containing neurotransmitters are released by ________ when the action potential arrives.

Exocytosis

The area in the center of the A band that contains no thin filaments is the

H band

Muscle fibers differ from "typical cells" in that muscle fibers:

Have many nuclei

Each skeletal muscle fiber contains ________ myofibrils.

Hundreds to thousands

The region of the sarcomere that always contains only thin filaments is the

I band

How would a drug that blocks acetylcholine receptors at the motor end plate affect skeletal muscle?

It would cause flaccid paralysis (muscles are relaxed and unable to contract).

How would the loss of acetylcholinesterase from the motor end plate affect skeletal muscle?

It would cause spastic paralysis (muscles are contracted and unable to relax).

Na+ and K+ use ________ to cross the plasma membrane.

Leak Channels

In a sarcomere, thick filaments are linked laterally by proteins of the

M Line

Cellular membrane potential is measured in

Millivolts

Identify the structures labeled "1." **

Mitochondria

A single motor neuron together with all the muscle fibers it innervates is called a(n)

Motor unit

Interactions between actin and myosin filaments of the sarcomere are responsible for

Muscle contraction

Skeletal muscle fibers are formed from embryonic cells called

Myoblasts

________ are stem cells located between the endomysium and sarcolemma that function in the repair of damaged muscle tissue.

Myosatellite Cells

Cross-bridges are portions of

Myosin molecules

Why is there partial relaxation in graph (c)? &&

Nerve stimulation frequency is below maximum.

Each skeletal muscle fiber is controlled by a motor neuron at a single

Neuromuscular junction

Nerves and blood vessels that service the muscle fibers are located in the connective tissues of the:

Perimysium

If potassium channels were blocked, the ________ phase of the action potential would not occur normally.

Repolarization

The plasma membrane of skeletal muscle is called the:

Sarcolemma

The repeating contractile unit of a skeletal muscle fiber is the:

Sarcomere

Since each myofibril is attached at either end of the muscle fiber, when sarcomeres shorten, the muscle fiber:

Shortens

The structural explanation of how a muscle fiber contracts is called the

Sliding filament theory

Which of the following best describes the term titin?

Substance that accounts for elasticity of resting muscle

The narrow space between the synaptic terminal and the muscle fiber is the

Synaptic Cleft

At each end of the muscle, the collagen fibers of the epimysium, and each perimysium and endomysium, come together to form a:

Tendon

The bundle of collagen fibers at the end of a skeletal muscle that attaches the muscle to bone is called a(n)

Tendon

What is thought to happen in a muscle during the response shown in graph (a)?

There is a gradual increase in the concentration of calcium ions in the sarcoplasm.

The complex of a transverse tubule and two adjacent terminal cisternae is known as a(n)

Triad

At rest, active sites on the actin are blocked by

Tropomyosin molecules.

The rapid rise and fall in force produced by a muscle fiber after a single action potential is a(n)

Twitch

Each thin filament consists of

Two protein strands coiled helically around each other.

Which of the following best describes the term "Z line"?

Where thin filaments are anchored

Which of the following muscles would contract more forcefully?

a muscle receiving 20 to 25 action potentials per second

The skeletal muscle complex known as the triad consists of

a transverse tubule and two terminal cisternae.

Triggering of the muscle action potential occurs after

acetylcholine binds to chemically gated channels in the motor end plate membrane.

The most important factor in decreasing the intracellular concentration of calcium ion after contraction is

active transport of calcium into the sarcoplasmic reticulum.

Creatine phosphate

acts as an energy reserve in muscle tissue.

During the recovery period, the body's need for oxygen is increased because

additional oxygen is required to restore energy reserves consumed during exercise.

A resting muscle generates most of its ATP by

aerobic metabolism of fatty acids.

Decreased blood flow to a muscle could result in all of the following except

an increase in intracellular glycogen.

After heavy exercise, if energy reserves in a muscle are depleted, ________ occurs.

an oxygen debt

Which process employs exocytosis?

chemical synapse

What is the contraction in graph (d) called?

complete tetanus

When a muscle is stimulated repeatedly at a high rate, eliminating a relaxation phase, the amount of tension gradually increases to a steady maximum tension. This is called

complete tetanus.

Physical evidence that supports the sliding filament theory of muscle contraction includes:

decreased width of the H band during contraction.

The synchronous contraction of a single motor unit is known as a(n)

fasciculation.

Large-diameter, densely packed myofibrils, large glycogen reserves, and few mitochondria are characteristics of

fast fibers.

During the Cori cycle, in the liver,

glucose is produced from lactate.

A membrane potential at -80 mV is

in the refractory period

A muscle producing tension that peaks and falls at intermediate stimulus rates is said to be in

incomplete tetanus.

The type of contraction in which the muscle fibers do not shorten is called

isometric

The muscle weakness of myasthenia gravis results from

loss of acetylcholine receptors in the end-plate membrane.

The Na+/K+ ion pump is responsible for

maintaining the sodium/potassium concentration gradients constant.

When acetylcholine binds to receptors at the motor end plate, the end plate membrane becomes

more permeable to sodium ions.

During activities requiring aerobic endurance,

most of the muscle's energy is produced in mitochondria.

Receptors for acetylcholine are located on the

motor end plate.

Neurons and ________ have electrically excitable membranes that propagate action potentials.

muscle cells

In an isotonic contraction,

muscle tension exceeds the load and the muscle lifts the load.

In which of the following would the motor units have the fewest muscle fibers?

muscles that control the eyes

To produce a contraction similar to the one in graph (b), the muscle.. &&&&&

must be stimulated again before it has relaxed from the previous stimulation.

Communication between axons and muscle fibers occurs at specialized synapses called

neuromuscular junctions.

At peak levels of muscle exertion, the mitochondria can supply ________ of the energy required by the muscle.

only about one-third

Of the following clinical conditions affecting skeletal muscle, which is caused by a virus? rigor mortis polio Duchenne muscular dystrophy tetanus botulism

polio

The advantage of having many nuclei in a skeletal muscle fiber is the ability to:

produce large amounts of the muscle proteins needed for muscle contraction.

The increase in muscle tension that is produced by increasing the number of active motor units is called

recruitment.

Fast muscle fibers can adapt to aerobic metabolism by generating more mitochondria in response to

repeated, exhaustive stimulation.

After death, muscle fibers run out of ATP and calcium begins to leak from the sarcoplasmic reticulum into the sarcoplasm. This results in a condition known as

rigor mortis.

Excitation- Contraction Coupling is the

sequence of processes that links the action potential to contraction.

The type of muscle fiber that is most resistant to fatigue is the ________ fiber.

slow

Which of the following hormones directly stimulates growth of muscle tissue, leading to increased muscle mass?

testosterone

Membrane potential is

the electrical gradient of a cell.

Which of the following acts as an ATPase during the contraction cycle of muscle?

the head portion of the myosin molecule

Which of the following become connected by myosin cross-bridges during muscle contraction?

thin filaments and thick filaments

The action potential is conducted deep into a skeletal muscle fiber by

transverse tubules.

When calcium ion binds to troponin,

tropomyosin moves into the groove between the helical actin strands.

At rest, the tropomyosin molecule is held in place by

troponin molecules.

If a second stimulus arrives before the relaxation phase has ended, a second, more powerful contraction occurs. This is called

wave summation.

Which of the following is not a type of motor unit?

white-slow twitch