Mastering A&P Chapter 10

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Which of the following statements is false? a) Cardiac muscle stimulation is neural. b) Cardiac muscle contractions cannot be summated. c) Skeletal muscle contractions may be summated. d) Skeletal muscle stimulation is neural. e) Cardiocytes are interconnected through intercalated discs.

a) Cardiac muscle stimulation is neural

Which of the following is most directly responsible for the coupling of excitation to contraction of skeletal muscle fibers? a) Acetylcholine. b) Calcium ions. c) Sodium ions. d) Action potentials.

b) Calcium ions

A myosin head binds to which molecule to form a cross bridge? a) troponin b) actin c) tropomyosin

b) actin

At each end of the muscle, the collagen fibers of the epimysium, and each perimysium and endomysium, come together to form a a) satellite cell. b) tendon. c) ligament. d) tenosynovium. e) sheath.

b) tendon

Which of the following is involved in the power stroke? a) Z lines b) myofibrils c) myosin d) tropomyosin

c) myosin

When calcium is released inside a muscle cell, what does it bind to? a) tropomyosin b) actin c) troponin d) myosin

c) troponin

After a power stroke, the myosin head must detach from actin before another power stroke can occur. What causes cross bridge detachment? a) ATP binds to the myosin head. b) Acetylcholine binds to receptors in the junctional folds of the sarcolemma. c) Calcium ions bind to troponin. d) ADP and inorganic phosphate are bound to the myosin head.

a) 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? a) Acetylcholine is degraded by acetylcholinesterase. b) Acetylcholine is transported into the postsynaptic neuron by receptor-mediated endocytosis. c) Acetylcholine diffuses away from the cleft. d) Acetylcholine is transported back into the axon terminal by a reuptake mechanism.

a) Acetylcholine is degraded by acetylcholinesterase

Calcium ions couple excitation of a skeletal muscle fiber to contraction of the fiber. Where are calcium ions stored within the fiber? a) Calcium ions are stored in the sarcoplasmic reticulum. b) Calcium ions are stored in the transverse tubules. c) Calcium ions are stored in the mitochondria. d) Calcium ions are stored in the nuclei.

a) Calcium ions are stored in the sarcoplasmic reticulum

When does cross bridge cycling end? a) Cross bridge cycling ends when sufficient calcium has been actively transported back into the sarcoplasmic reticulum to allow calcium to unbind from troponin. b) Cross bridge cycling ends when ATP binds to the myosin head. c) Cross bridge cycling ends when calcium release channels in the sarcoplasmic reticulum open. d) Cross bridge cycling ends when calcium ions are passively transported back into the sarcoplasmic reticulum.

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

Sodium and potassium ions do not diffuse in equal numbers through ligand-gated cation channels. Why? a) The inside surface of the sarcolemma is negatively charged compared to the outside surface. Sodium ions diffuse inward along favorable chemical and electrical gradients. b) The inside surface of the sarcolemma is negatively charged compared to the outside surface. Potassium ions diffuse inward along favorable chemical and electrical gradients. c) The outside surface of the sarcolemma is negatively charged compared to the inside surface. Potassium ions diffuse outward along favorable chemical and electrical gradients. d) The outside surface of the sarcolemma is negatively charged compared to the inside surface. Sodium ions diffuse outward along favorable chemical and electrical gradients.

a) 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 is the relationship between the number of motor neurons recruited and the number of skeletal muscle fibers innervated? a) Typically, hundreds of skeletal muscle fibers are innervated by a single motor neuron. b) Motor neurons always innervate thousands of skeletal muscle fibers. c) A motor neuron typically innervates only one skeletal muscle fiber. d) A skeletal muscle fiber is innervated by multiple motor neurons.

a) Typically, hundred of skeletal muscle fibers are innervated by a single motor neuron

How is acetylcholine (ACh) removed from the synaptic cleft? a) acetylcholinesterase (AChE; an enzyme) b) a reuptake pump on the axon terminal c) diffusion away from the synaptic cleft

a) acetylcholinesterase (AChE; an enzyme)

Creatine phosphate a) acts as an energy reserve in muscle tissue. b) is only formed during strenuous exercise. c) can replace ATP in binding to myosin molecules during contraction. d) cannot transfer its phosphate group to ADP. e) is produced by the process of anaerobic respiration.

a) acts as an energy reserve in muscle tissue

A muscle producing its maximum tension is in __________. a) complete tetanus b) rigor mortis c) treppe d) incomplete tetanus

a) complete tetanus

What is the type of chemical reaction used to rebuild ADP into ATP? a) dehydration synthesis b) rehydration synthesis c) hydrolysis

a) dehydration synthesis

ATP binding leads to which of the following actions? a) detaching and resetting cross-bridges b) cross-bridge formation c) pivoting of the myosin head d) exposure of active sites on actin

a) detaching and resetting cross-bridges

The dense layer of connective tissue that surrounds an entire skeletal muscle is the a) epimysium. b) tendon. c) perimysium. d) fascicle. e) endomysium.

a) epimysium

What means of membrane transport is used to release the neurotransmitter into the synaptic cleft? a) exocytosis b) a channel c) a protein carrier

a) exocytosis

The neuromuscular junction is a connection between a neuron and a __________. a) muscle fiber b) synaptic terminal c) myofibril d) vesicle

a) muscle fiber

Acetylcholine receptors are primarily located __________. a) on the motor end plate b) on the synaptic terminal c) inside vesicles d) inside the muscle fiber

a) on the motor end plate

Which organelle completely surrounds each myofibril inside a muscle fiber? a) sarcoplasmic reticulum b) calcium c) fascicle d) nucleus

a) sarcoplasmic reticulum

Which type of muscle tissue has the greatest effect on the body's heat production? a) skeletal b) cardiac c) smooth d) All of these muscle types have about the same effect on the body's heat production.

a) skeletal

The end of a neuron, where acetylcholine-filled vesicles are located, is called the __________. a) synaptic terminal b) motor end plate c) synaptic cleft d) acetylcholine receptor

a) synaptic terminal

An action potential in the muscle fiber causes __________. a) the muscle fiber to contract b) acetylcholinesterase to break down acetylcholine c) acetylcholine to bind to receptors on the motor end plate d) the release of acetylcholine into the synaptic cleft

a) the muscle fiber to contract

What is the synaptic cleft? a) the space between the synaptic terminal and the motor end plate b) the region of the neuron containing synaptic vesicles c) the step where acetylcholinesterase (AChE) breaks down, or cleaves, acetylcholine d) the border between the motor end plate and the sarcolemma

a) the space between the synaptic terminal and the motor end plate

Which of the following phrases best describes how excitation is coupled to contraction in skeletal muscle fibers? a) through calcium release from the sarcoplasmic reticulum b) through T tubules c) through cross-bridge formation d) through electrical impulses travelling along the sarcolemma

a) through calcium release from the sarcoplasmic reticulum

When calcium ion binds to troponin, a) tropomyosin moves into the groove between the helical actin strands. b) active sites on the myosin are exposed. c) myosin shortens. d) muscle relaxation occurs. e) actin heads will bind to myosin.

a) tropomyosin moves into the groove between the helical actin strands

Aerobic metabolism normally provides ________ percent of the ATP demands of a resting muscle cell. a) 70 b) 95 c) 100 d) 50 e) 25

b) 95

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? a) Acetylcholine binds to its receptor in the junctional folds of the sarcolemma. Its receptor is linked to a G protein. b) Acetylcholine is released by axon terminals of the motor neuron. c) When the action potential reaches the end of the axon terminal, voltage-gated sodium channels open and sodium ions diffuse into the terminal. d) Acetylcholine is released and moves across the synaptic cleft bound to a transport protein.

b) Acetylcholine is released by axon terminals of the motor neuron

What specific event triggers the uncovering of the myosin binding site on actin? a) Calcium ions bind to tropomyosin and change its shape. b) Calcium ions bind to troponin and change its shape. c) Calcium release channels open in the sarcoplasmic reticulum, and calcium levels rise in the sarcoplasm. d) Sodium ions bind to troponin and change its shape.

b) Calcium ions bind to troponin and change its shape

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? a) Excitation refers to the release of calcium ions from the sarcoplasmic reticulum. b) Excitation, in this case, refers to the propagation of action potentials along the sarcolemma. c) Excitation refers to the shape change that occurs in voltage-sensitive proteins in the sarcolemma. d) Excitation refers to the propagation of action potentials along the axon of a motor neuron.

b) 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 a) M line. b) I band. c) A band. d) Z line. e) H band.

b) I band

Which of the following processes produces 36 ATP? a) glycolysis b) Krebs cycle and oxidative phosphorylation c) hydrolysis of creatine phosphate

b) Krebs cycle and oxidative phosphorylation

The muscle action potentials that initiate contraction are transmitted from the sarcolemma into the interior of the muscle fiber by __________. a) the sarcoplasmic reticulum b) T tubules c) myofilaments d) myofibrils

b) T tubules

Acetylcholine binds to its receptor in the sarcolemma and triggers __________. a) the opening of calcium-release channels b) the opening of ligand-gated cation channels c) the opening of ligand-gated anion channels d) the opening of voltage-gated calcium channels

b) The opening of ligand-gates cation channels

What structure is the functional unit of contraction in a skeletal muscle fiber? a) The junctional folds of the sarcolemma b) The sarcomere c) The triad d) The cross bridge

b) The sarcomere

During neuromuscular transmission, the axon terminals release __________. a) sodium ions b) acetylcholine c) calcium ions d) acetylcholinesterase

b) acetylcholine

In a neuromuscular junction, synaptic vesicles in the motor neuron contain which neurotransmitter? a) dopamine b) acetylcholine (ACh) c) norepinephrine d) serotonin

b) acetylcholine (ACh)

Myosin molecules form cross-bridges when they attach to __________. a) troponin b) actin c) tropomyosin d) calcium

b) actin

The sarcoplasmic reticulum contains __________. a) troponin b) calcium c) T tubules d) myofilaments

b) calcium

What energizes the power stroke? a) binding of ATP b) hydrolysis of ATP c) calcium

b) hydrolysis of ATP

Muscle fatigue occurs due to a buildup of __________ and __________ in pH. a) creatine phosphate; increase b) lactic acid; decrease c) creatine phosphate; decrease d) lactic acid; increase

b) lactic acid; decrease

During activities requiring aerobic endurance a) fatigue occurs in a few minutes. b) most of the muscle's energy is produced in mitochondria. c) oxygen debts are common. d) glycogen and glycolysis are the primary sources of reserve energy. e) oxygen is not required.

b) most of the muscle's energy is produced in mitochondria

Skeletal muscle fibers are formed from embryonic cells called a) myomeres. b) myoblasts. c) sarcomeres. d) myofibrils. e) fascicles.

b) myoblasts

Resting smooth muscle can be stretched without developing much tension because of its __________. a) contractility b) plasticity c) extensibility d) elasticity

b) plasticity

The role of acetylcholinesterase in the neuromuscular junction is to __________. a) increase the sodium permeability of the motor end plate b) remove acetylcholine from the synaptic cleft c) release acetylcholine from the synaptic terminal d) generate a muscle action potential

b) remove acetylcholine from the synaptic cleft

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 a) tetany. b) rigor mortis. c) oxygen debt. d) depolarization. e) treppe.

b) rigor mortis

The action potential in skeletal muscle fibers is generated by the __________. a) sarcoplasmic reticulum b) sarcolemma c) sarcoplasm d) sarcophagus

b) sarcolemma

The type of muscle fiber that is most resistant to fatigue is the ________ fiber. a) fast b) slow c) high-density d) anaerobic e) intermediate

b) slow

Which of the following best describes the term sarcoplasmic reticulum? a) largely made of myosin molecules b) storage and release site for calcium ions c) thin filaments are anchored here d) repeating unit of striated myofibrils e) protein that accounts for elasticity of resting muscle

b) storage and release site for calcium ions

The narrow space between the synaptic terminal and the muscle fiber is the a) synaptic knob. b) synaptic cleft. c) M line. d) motor end plate. e) motor unit.

b) synaptic cleft

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? a) T tubule b) terminal cisternae of the sarcoplasmic reticulum c) sarcolemma d) cytosol

b) terminal cisternae of the sarcoplasmic reticulum

T tubules and the terminal cisternae are clustered into structures called __________. a) sarcomeres b) triads c) fascicles d) myofibrils

b) triads

When the sarcomere is at rest, what is covering the active sites on actin? a) myosin b) tropomyosin c) cross-bridges d) troponin

b) tropomyosin

The binding of calcium to which molecule causes the myosin binding sites to be exposed? a) tropomyosin b) troponin c) actin

b) troponin

To what regulatory protein does calcium bind during the initiation of the contraction cycle in skeletal muscle fibers? a) actin b) troponin c) myosin d) tropomyosin

b) troponin

Which type of muscle fiber has a large quantity of glycogen and mainly uses glycolysis to synthesize ATP? a) red slow twitch fibers b) white fast twitch fibers

b) white fast twitch fibers

The cross bridge cycle is a series of molecular events that occur after excitation of the sarcolemma. What is a cross bridge? a) Calcium bound to troponin b) ATP bound to a myosin head c) A myosin head bound to actin d) Troponin bound to tropomyosin

c) A myosin head bound to actin

The binding of the neurotransmitter to receptors on the motor end plate causes which of the following to occur? a) Binding causes chemically gated potassium channels to open in the motor end plate. b) Binding causes potassium voltage-gated channels to open in the motor endplate. c) Binding of the neurotransmitter causes chemically gated sodium channels to open in the motor end plate. d) Binding causes voltage-gated sodium channels to open in the motor endplate.

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

Excitation of the sarcolemma is coupled or linked to the contraction of a skeletal muscle fiber. What specific event initiates the contraction? a) Action potentials propagate into the interior of the skeletal muscle fiber. b) Sodium release from the sarcoplasmic reticulum initiates the contraction. c) Calcium release from the sarcoplasmic reticulum initiates the contraction. d) Voltage-sensitive proteins change shape.

c) Calcium release from the sarcoplasmic reticulum initiates the contraction.

The "rest and recovery" period, where the muscle restores depleted reserves, includes all of the following processes EXCEPT __________. a) Glycogen is synthesized from glucose molecules. b) ATP is used to rephosphorylate creatine into creatine phosphate. c) Pyruvic acid is converted back to lactic acid. d) Oxygen rebinds to myoglobin.

c) Pyruvic acid is converted back to lactic acid

Calcium entry into the axon terminal triggers which of the following events? a) Cation channels open and sodium ions enter the axon terminal while potassium ions exit the axon terminal. b) Acetylcholine is released into the cleft by active transporters in the plasma membrane of the axon terminal. c) Synaptic vesicles fuse to the plasma membrane of the axon terminal and release acetylcholine. d) Acetylcholine binds to its receptor.

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

How does the myosin head obtain the energy required for activation? a) The energy comes from oxidative phophorylation. b) The energy comes from the hydrolysis of GTP. c) The energy comes from the hydrolysis of ATP. d) The energy comes from the direct phosphorylation of ADP by creatine phosphate.

c) The energy comes from the hydrolysis of GTP

Which of the following proteins contains the active site involved in cross-bridge formation? a) tropomyosin b) troponin c) actin d) myosin

c) actin

During the recovery period the body's need for oxygen is increased because a) muscle cells are producing energy anaerobically. b) the muscles are not producing ATP. c) additional oxygen is required to restore energy reserves consumed during exercise. d) the individual is panting. e) the liver requires more oxygen to produce lactic acid.

c) additional oxygen is required to restore energy reserves consumed during exercise

What causes the vesicles inside a neuron to fuse with the plasma membrane? a) acetylcholine binding to acetylcholine receptors b) an action potential in the muscle fiber c) an action potential in the neuron d) acetylcholine being broken down by acetylcholinesterase

c) an action potential in the neuron

What causes the release of calcium from the terminal cisternae of the sarcoplasmic reticulum within a muscle cell? a) ATP b) troponin c) arrival of an action potential d) calcium ion pump

c) arrival of an action potential

What causes the myosin head to disconnect from actin? a) binding of calcium b) binding of troponin c) binding of ATP d) hydrolysis of ATP

c) binding of ATP

Action potentials travel the length of the axons of motor neurons to the axon terminals. These motor neurons __________. a) extend from the brain to the sarcolemma of a skeletal muscle fiber b) extend from the spinal cord to the sarcolemma of a skeletal muscle fiber c) extend from the brain or spinal cord to the sarcolemma of a skeletal muscle fiber d) arise in the epimysium of a skeletal muscle and extend to individual skeletal muscle fibers

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

Which of the following processes produces molecules of ATP and has two pyruvic acid molecules as end products? a) hydrolysis of creatine phosphate b) Krebs cycle and oxidative phosphorylation c) glycolysis

c) glycolysis

Muscle fibers differ from "typical cells" in that muscle fibers a) lack a plasma membrane. b) are very small. c) have many nuclei. d) have large gaps in the cell membrane. e) lack mitochondria.

c) have many nuclei

The muscle weakness of myasthenia gravis results from a) inability of the muscle fiber to produce ATP. b) excessive acetylcholinesterase that destroys the neurotransmitter. c) loss of acetylcholine receptors in the end-plate membrane. d) insufficient acetylcholine release from presynaptic vesicles. e) the motor neuron action potential being too small to shock the muscle fibers.

c) loss of acetylcholine receptors in the end-plate membrane

Myofibrils are __________. a) proteins that cover active sites on actin b) bundles of muscle cells inside a whole muscle c) made of a series of sarcomeres d) connections between actin and myosin

c) made of a series of sarcomeres

Which thick filament binds to actin once its active binding sites are exposed? a) actin b) troponin c) myosin d) tropomyosin

c) myosin

A patient takes a medication that blocks ACh receptors of skeletal muscle fibers. What is this drug's effect on skeletal muscle contraction? a) causes a strong contraction similar to a "charlie horse" cramp b) produces a strong, continuous state of contraction c) reduces the muscle's ability for contraction d) increases tone in the muscle e) increases the muscle's excitability

c) reduces the muscle's ability for contraction

The plasma membrane of a skeletal muscle fiber is called the a) sarcoplasmic reticulum. b) sarcosome. c) sarcolemma. d) sarcoplasm. e) sarcomere.

c) sarcolemma

The muscle action potential penetrates into a fiber along the __________. a) sarcoplasmic reticulum b) Z discs c) transverse tubules d) neuromuscular junction

c) transverse tubules

Which component of a thin filament binds to calcium once the calcium ion is released from the sarcoplasmic reticulum? a) tropomyosin b) myosin c) troponin d) actin

c) troponin

Inside a neuron, acetylcholine is contained within __________. a) acetylcholine receptors b) the synaptic cleft c) vesicles d) the motor end plate

c) vesicles

When an action potential arrives at the axon terminal of a motor neuron, which ion channels open? a) chemically gated calcium channels b) voltage-gated potassium channels c) voltage-gated calcium channels d) voltage-gated sodium channels

c) voltage-gated calcium channels

A triad is composed of a T-tubule and two adjacent terminal cisternae of the sarcoplasmic reticulum. How are these components connected? a) Potassium leak channels. b) Myosin cross-bridge binding sites. c) Voltage-gated sodium channels. d) A series of proteins that control calcium release.

d) A series of proteins that control calcium release

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

d) All of these are true of cardiac fibers

To increase muscle tension, the nervous system can __________. a) increase the number of active motor units b) recruit larger motor units c) increase the stimulation frequency d) All of these can increase muscle tension.

d) All of these can increase muscle tension

Cycling of myosin cross-bridges results in ___________. a) ATP hydrolysis b) force production c) muscle shortening d) Repeated cycling of cross-bridges causes all of these effects.

d) Repeated cycling of cross-bridges causes all of these effects

Malignant hyperthermia (MH) is a rare genetic disease in which the sarcoplasmic reticulum leaks calcium when the patient is put under general anesthesia. Which of the following best describes how anesthesia would affect the skeletal muscles of a patient with MH? a) The muscles would relax because of calcium being pumped back into the sarcoplasmic reticulum. b) The muscles would contract because of increased nerve stimulation. c) The muscles would contract because of increased action potential generation in the sarcolemma. d) The muscles would contract because of calcium binding to troponin.

d) The muscles would contract because of calcium binding to troponin

What happens immediately after the myosin head binds to the active site on actin? a) Tropomyosin moves away from the active site on actin. b) The myosin head detaches from the active site on actin. c) ATP binds to the myosin head. d) The myosin head pivots, moving the actin strand.

d) The myosin head pivots, moving the actin strand

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

d) They are large in diameter

A single muscle action potential will normally be followed by __________. a) two pulses of calcium ion release b) treppe c) incomplete tetanus d) a single pulse of calcium ion release

d) a single pulse of calcium ion release

The skeletal muscle complex known as the triad consists of a) actin, myosin, and sarcomeres. b) filaments, myofibrils, and sarcomeres. c) A bands, H bands, and I bands. d) a transverse tubule and two terminal cisternae. e) actin, myosin, and filaments.

d) a transverse tubule and two terminal cisternae

The cytoplasm of the neuromuscular terminal contains vesicles filled with molecules of the neurotransmitter a) epinephrine. b) adrenaline. c) norepinephrine. d) acetylcholine. e) antidiuretic hormone.

d) acetylcholine

Muscles are attached to bones by tendons or __________. a) superficial fascia b) perimysium c) ligaments d) aponeuroses

d) aponeuroses

In response to action potentials arriving along the transverse tubules, the sarcoplasmic reticulum releases a) hydrogen ions. b) acetylcholine. c) sodium ions. d) calcium ions. e) potassium ions.

d) calcium ions

Muscle tissue, one of the four basic tissue groups, consists chiefly of cells that are highly specialized for a) conduction. b) cushioning. c) secretion. d) contraction. e) peristalsis.

d) contraction

Titin is a(n) __________. a) calcium-binding protein b) tropomyosin-binding protein c) thin filament protein d) elastic protein

d) elastic protein

The capillaries that wrap around each muscle fiber are located within the __________. a) epimysium b) sarcolemma c) perimysium d) endomysium

d) endomysium

Synaptic vesicles contain neurotransmitters that are released by ________ when the action potential arrives. a) hydrolysis b) sodium c) endocytosis d) exocytosis e) apoptosis

d) exocytosis

Inside a muscle, bundles of single muscle fibers form __________. a) sarcomeres b) T tubules c) thick filaments d) fascicles

d) fascicles

The __________ type of muscle fiber has relatively few mitochondria. a) intermediate b) slow c) cardiac d) fast

d) fast

Large-diameter, densely packed myofibrils, large glycogen reserves, and few mitochondria are characteristics of a) red muscles. b) intermediate fibers. c) slow fibers. d) fast fibers. e) fatty muscles.

d) fast fibers

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

d) intercalated disks

The type of contraction in which the muscle fibers do not shorten is called a) concentric. b) treppe. c) tetany. d) isometric. e) isotonic.

d) isometric

In an isotonic contraction, a) many twitches always fuse into one. b) postural muscles stabilize the vertebrae. c) tension rises and falls but the muscle length is constant. d) muscle tension exceeds the load and the muscle lifts the load. e) the peak tension is less than the load.

d) 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? a) postural muscles of the back b) muscles of the neck c) thigh muscles d) muscles that control the eyes e) calf muscles

d) muscles that control the eyes

A thin layer of connective tissue that surrounds a muscle fascicle is called the __________. a) endomysium b) epimysium c) tendon d) perimysium

d) perimysium

Which of the following best describes the term sarcomere? a) thin filaments are anchored here b) largely made of myosin molecules c) protein that accounts for elasticity of resting muscle d) repeating unit of striated myofibrils e) storage site for calcium ions

d) repeating unit of striated myofibrils

The repeating unit of a skeletal muscle fiber is the a) myofilament. b) sarcolemma. c) myofibril. d) sarcomere. e) sarcoplasmic reticulum.

d) sarcomere

Z lines define the edges of which of the following? a) myofibrils b) cross-bridges c) myosin d) sarcomeres

d) sarcomeres

In response to an action potential along the transverse tubules, the __________ release(s) calcium ions into the sarcoplasm. a) thin filaments b) troponin molecules c) calcitonin d) sarcoplasmic reticulum

d) sarcoplasmic reticulum

The bundle of collagen fibers at the end of a skeletal muscle that attaches the muscle to bone is called a(n) a) ligament. b) epimysium. c) myofibril. d) tendon. e) fascicle.

d) tendon

Myosin molecules form what part of the sarcomere? a) thin filament b) actin c) tropomyosin d) thick filament

d) thick filaments

What is name given to the regularly spaced infoldings of the sarcolemma? a) sarcoplasmic reticulum b) motor endplates c) terminal cisternae d) transverse or T tubules

d) transverse or T tubules

Which of the following causes the active site on actin to be exposed or uncovered? a) cross-bridge formation b) troponin releasing calcium c) calcium entering the sarcoplasmic reticulum d) tropomyosin shifting position

d) tropomyosin shifting position

Which of the following most correctly describes excitation in the context of excitation-contraction coupling in skeletal muscle? a) the formation of cross-bridges b) the binding of calcium to troponin c) the release of calcium by the sarcoplasmic reticulum d) the generation of an action potential in the sarcolemma

d)the generation of an action potential in the sarcolemma

During anaerobic glycolysis a) carbohydrate is metabolized. b) ATP is produced. c) pyruvic acid is produced. d) oxygen is not consumed. e) All of the answers are correct.