Mastering A & P Chapter 10- Questions

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

95

The cross bridge cycle is a series of molecular events that occur after excitation of the sarcolemma. What is a cross bridge?

A myosin head bound to actin

A triad is composed of a T-tubule and two adjacent terminal cisternae of the sarcoplasmic reticulum. How are these components connected?

A series of proteins that control calcium release.

After a power stroke, the myosin head must detach from actin before another power stroke can occur. What causes cross bridge detachment?

ATP binds to the myosin head.

Action potential propagation in a skeletal muscle fiber ceases when acetylcholine is removed from the synaptic cleft. Which of the following mechanisms ensures a rapid and efficient removal of acetylcholine?

Acetylcholine is degraded by acetylcholinesterase.

The neuromuscular junction is a well-studied example of a chemical synapse. Which of the following statements describes a critical event that occurs at the neuromuscular junction?

Acetylcholine is released by axon terminals of the motor neuron.

When comparing slow muscle fibers to fast muscle fibers, slow fibers 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 of the answers

During anaerobic glycolysis oxygen is not consumed. pyruvic acid is produced. carbohydrate is metabolized. ATP is produced. All of the answers are correct.

All of the answers are correct.

In rigor mortis the myosin heads are attached to actin. cross-bridge cycling is absent. muscles are inextensible. ATP is depleted. All of the answers are correct.

All of the answers are correct.

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

All of the answers are correct.

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

All of the answers are correct.

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

All of the answers are correct.

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

All of the answers are correct.

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

All of the answers are correct.

Which of these is true of cardiac muscle fibers? Cardiac fibers branch. Cardiac fibers have a long twitch duration compared to skeletal fibers. Cardiac fibers have a single nucleus. All of these are true of cardiac fibers.

All of these are true of cardiac fibers.

The binding of the neurotransmitter to receptors on the motor end plate causes which of the following to occur?

Binding of the neurotransmitter causes chemically gated sodium channels to open in the motor end plate.

Calcium ions couple excitation of a skeletal muscle fiber to contraction of the fiber. Where are calcium ions stored within the fiber? .

Calcium ions are stored in the sarcoplasmic reticulum.

What specific event triggers the uncovering of the myosin binding site on actin? .

Calcium ions bind to troponin and change its shape.

Which of the following is most directly responsible for the coupling of excitation to contraction of skeletal muscle fibers?

Calcium ions.

Excitation of the sarcolemma is coupled or linked to the contraction of a skeletal muscle fiber. What specific event initiates the contraction?

Calcium release from the sarcoplasmic reticulum initiates the contraction.

Which of the following statements is false?

Cardiac muscle stimulation is neural.

When does cross bridge cycling end?

Cross bridge cycling ends when sufficient calcium has been actively transported back into the sarcoplasmic reticulum to allow calcium to unbind from troponin.

Excitation-contraction coupling is a series of events that occur after the events of the neuromuscular junction have transpired. The term excitation refers to which step in the process?

Excitation, in this case, refers to the propagation of action potentials along the sarcolemma.

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

I band.

The "rest and recovery" period, where the muscle restores depleted reserves, includes all of the following processes EXCEPT __________.

Pyruvic acid is converted back to lactic acid.

Cycling of myosin cross-bridges results in ___________.

Repeated cycling of cross-bridges causes all of these effects.

Calcium entry into the axon terminal triggers which of the following events?

Synaptic vesicles fuse to the plasma membrane of the axon terminal and release acetylcholine.

The muscle action potentials that initiate contraction are transmitted from the sarcolemma into the interior of the muscle fiber by __________.

T tubules

How does the myosin head obtain the energy required for activation?

The energy comes from the hydrolysis of ATP.

Sodium and potassium ions do not diffuse in equal numbers through ligand-gated cation channels. Why?

The inside surface of the sarcolemma is negatively charged compared to the outside surface. Sodium ions diffuse inward along favorable chemical and electrical gradients.

What happens immediately after the myosin head binds to the active site on actin? .

The myosin head pivots, moving the actin strand.

What structure is the functional unit of contraction in a skeletal muscle fiber?

The sarcomere

The soleus muscle is very red in color. Which of these statements about soleus muscle fibers is FALSE?

They are large in diameter.

Which of these is not a property of slow muscle fibers? They resist fatigue. They are rich in myoglobin. They contract slowly. They are large in diameter.

They are large in diameter.

What is the relationship between the number of motor neurons recruited and the number of skeletal muscle fibers innervated?

Typically, hundreds of skeletal muscle fibers are innervated by a single motor neuron.

Sarcomere is best defined as __________.

a repeating functional unit of striated muscle

Which of the following is important to increasing efficiency in tension production?

a shortened relaxation phase

A single muscle action potential will normally be followed by __________.

a single pulse of calcium ion release

A single muscle stimulus will normally be followed by __________.

a single pulse of calcium ion release

The skeletal muscle complex known as the triad consists of

a transverse tubule and two terminal cisternae.

During neuromuscular transmission, the axon terminals release __________.

acetylcholine

In a neuromuscular junction, synaptic vesicles in the motor neuron contain which neurotransmitter?

acetylcholine (ACh)

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

acetylcholine.

How is acetylcholine (ACh) removed from the synaptic cleft?

acetylcholinesterase (AChE; an enzyme)

Which of the following situations could contribute to prolonged muscle contraction?

acetylcholinesterase not being produced

A myosin head binds to which molecule to form a cross bridge?

actin

Myosin molecules form cross-bridges when they attach to __________.

actin

Which of the following proteins contains the active site involved in cross-bridge formation?

actin

Creatine phosphate

acts as an energy reserve in muscle tissue.

What causes the vesicles inside a neuron to fuse with the plasma membrane?

an action potential in the neuron

Muscles are attached to bones by tendons or __________.

aponeuroses

What causes the release of calcium from the terminal cisternae of the sarcoplasmic reticulum within a muscle cell?

arrival of an action potential

What causes the myosin head to disconnect from actin?

binding of ATP

The sarcoplasmic reticulum contains __________.

calcium

A muscle producing its maximum tension for a prolonged period is in __________.

complete tetanus

A muscle producing its maximum tension is in __________.

complete tetanus

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

contraction.

ATP binding leads to which of the following actions?

detaching and resetting cross-bridges

Titin is a(n) __________.

elastic protein

Muscle fibers are directly surrounded by which thin layer of connective tissue?

endomysium

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

epimysium.

The sequence of processes that links the action potential to contraction is called

excitation-contraction coupling.

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

exocytosis

What means of membrane transport is used to release the neurotransmitter into the synaptic cleft?

exocytosis

Action potentials travel the length of the axons of motor neurons to the axon terminals. These motor neurons __________.

extend from the brain or spinal cord to the sarcolemma of a skeletal muscle fiber

Inside a muscle, bundles of single muscle fibers form __________.

fascicles

Muscles that move the eyeball have ________ fibers.

fast

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 lactic acid.

Fast fibers_______.

have low resistance to fatigue and quick twitches.

Skeletal Muscle fibers differ from other muscle fibers in that they

have many nuclei.

What energizes the power stroke?

hydrolysis of ATP

All of the following are found in both skeletal and cardiac muscle fibers except __________. sarcomeres intercalated disks striations mitochondria

intercalated disks

Which arrangement of the sarcomere gives rise to the M line?

is the point of connection for adjacent thick filaments

Muscle fatigue occurs due to a buildup of __________ and __________ in pH.

lactic acid; decrease

The muscle weakness of myasthenia gravis results from

loss of acetylcholine receptors in the end-plate membrane.

Myofibrils are __________.

made of a series of sarcomeres

During activities requiring aerobic endurance

most of the muscle's energy is produced in mitochondria

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

muscle contraction.

The neuromuscular junction is a connection between a neuron and a __________.

muscle fiber

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

muscles that control the eyes

Skeletal muscle fibers are formed from embryonic cells called

myoblasts.

Which of the following is involved in the power stroke?

myosin

Which thick filament binds to actin once its active binding sites are exposed?

myosin

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

neuromuscular junction.

Acetylcholine receptors are primarily located __________.

on the motor end plate

What is the function of the T Tubules?

part of coupling the action potential to contraction

A thin layer of connective tissue that surrounds a muscle fascicle is called the __________.

perimysium

Resting smooth muscle can be stretched without developing much tension because of its __________.

plasticity

Skeletal muscle does each of these EXCEPT __________.

pump blood

A patient takes a medication that blocks ACh receptors of skeletal muscle fibers. What is this drug's effect on skeletal muscle contraction?

reduces the muscle's ability for contraction

The role of acetylcholinesterase in the neuromuscular junction is to __________.

remove acetylcholine from the synaptic cleft

Which of the following best describes the term sarcomere?

repeating unit of striated myofibrils

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.

The action potential in skeletal muscle fibers is generated by the __________.

sarcolemma

The plasma membrane of a skeletal muscle fiber is called the

sarcolemma.

The repeating unit of a skeletal muscle fiber is the

sarcomere.

In response to an action potential along the transverse tubules, the __________ release(s) calcium ions into the sarcoplasm.

sarcoplasmic reticulum

Which organelle completely surrounds each myofibril inside a muscle fiber?

sarcoplasmic reticulum

Which type of muscle tissue has the greatest effect on the body's heat production?

skeletal

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

slow twitch

Which of the following best describes the term sarcoplasmic reticulum?

storage and release site for calcium ions

What is the function of the Sarcoplasmic Reticulum?

storage of calcium

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

synaptic cleft.

The end of a neuron, where acetylcholine-filled vesicles are located, is called the __________.

synaptic terminal

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.

The action potential on the muscle cell leads to contraction due to the release of calcium ions. Where are calcium ions stored in the muscle cell?

terminal cisternae of the sarcoplasmic reticulum

Which arrangement of the sarcomere gives rise to the Z line?

the boundary between adjacent sarcomeres

Which of the following most correctly describes excitation in the context of excitation-contraction coupling in skeletal muscle?

the generation of an action potential in the sarcolemma

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

the head portion of the myosin molecule

An action potential in the muscle fiber causes __________.

the muscle fiber to contract

Acetylcholine binds to its receptor in the sarcolemma and triggers __________.

the opening of ligand-gated cation channels

Which arrangement of the sarcomere gives rise to the H band?

the region of the resting sarcomere that only contains thick filaments

Which arrangement of the sarcomere gives rise to the I band?

the region of the sarcomere that contains only thin filaments

What is the synaptic cleft?

the space between the synaptic terminal and the motor end plate

Myosin molecules form what part of the sarcomere?

thick filament

Which of the following phrases best describes how excitation is coupled to contraction in skeletal muscle fibers?

through calcium release from the sarcoplasmic reticulum

What is name given to the regularly spaced infoldings of the sarcolemma?

transverse or T tubules

The muscle action potential penetrates into a fiber along the __________.

transverse tubules

T tubules and the terminal cisternae are clustered into structures called __________.

triads

When the sarcomere is at rest, what is covering the active sites on actin?

tropomyosin

When calcium ion binds to troponin,

tropomyosin moves into the groove between the helical actin strands

Which of the following causes the active site on actin to be exposed or uncovered?

tropomyosin shifting position

The binding of calcium to which molecule causes the myosin binding sites to be exposed?

troponin

To what regulatory protein does calcium bind during the initiation of the contraction cycle in skeletal muscle fibers?

troponin

When calcium is released inside a muscle cell, what does it bind to?

troponin

Which component of a thin filament binds to calcium once the calcium ion is released from the sarcoplasmic reticulum?

troponin

Inside a neuron, acetylcholine is contained within __________.

vesicles

When an action potential arrives at the axon terminal of a motor neuron, which ion channels open?

voltage-gated calcium channels