Chapter 10 online hw

Which of the following best describes the term Z line? protein that accounts for elasticity of resting muscle thin filaments are anchored here repeating unit of striated myofibrils largely made of myosin molecules storage site for calcium ions

thin filaments are anchored here

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

troponin

Muscles are attached to bones by tendons or __________. perimysium ligaments superficial fascia aponeuroses

aponeuroses

A(n) ________ can be described as a broad tendinous sheet. interstitium fasciae retinaculum tympanum aponeurosis

aponeurosis

Muscle tissue, one of the four basic tissue groups, consists chiefly of cells that are highly specialized for conduction. peristalsis cushioning. contraction secretion.

contraction

Fatigued muscles signify __________. accumulation of pyruvic acid oxygen recovery lowered body temperature decreased pH

decreased pH

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

dehydration synthesis

The increase in muscle tension that is produced by increasing the number of active motor units is called complete tetanus. incomplete tetanus. wave summation. treppe. recruitment.

recruitment

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

troponin

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

troponin

At rest, the tropomyosin molecule is held in place by actin molecules. calcium ions .troponin molecules. ATP molecules .myosin molecules.

troponin molecules

The rapid rise and fall in force produced by a muscle fiber after a single action potential is a(n) motor end plate potential. twitch. tetanus. unfused tetanus. muscle action potential.

twitch

Each thin filament consists of a rod-shaped structure with "heads" projecting from each end. a double strand of myosin molecules .six molecules coiled into a helical structure. chains of myosin molecules. two actin protein strands coiled helically around each other.

two actin protein strands coiled helically around each other.

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

voltage-gated calcium channels

If a second stimulus arrives before the relaxation phase has ended, a second, more powerful contraction occurs. This addition of one twitch to another is called wave summation. recruitment. complete tetanus. treppe. incomplete tetanus.

wave summation

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

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. Voltage-gated sodium channels. Potassium leak channels. Myosin cross-bridge binding sites.

A series of proteins that control calcium release.

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

ACh

Which of the following events directly occurs due to an action potential generated on the motor neuron? Na rushes into the sarcolemma. AChE breaks down ACh in the synaptic cleft ACh binds to ACh receptors. An action potential is generated on the muscle fiber. ACh is released at the synapse.

ACh is released at the synapse.

The characteristic muscle stiffness associated with rigor mortis is due to the inability of myosin filaments to detach from the active site on actin filaments. What molecule is essential for this detachment? calcium acetylcholinesterase acetylcholine ATP

ATP

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

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

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

Acetylcholine is released by axon terminals of the motor neuron.

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

All of the above

What causes the release of calcium ions into the sarcoplasm from the terminal cisterns? The binding of myosin heads to actin An action potential traveling along the t tubule The change in the shape of troponin Acetylcholine entering the sarcoplasm of the muscle fiber

An action potential traveling along the t tubule

The binding of the neurotransmitter to receptors on the motor end plate causes which of the following to occur? Binding causes voltage-gated sodium channels to open in the motor end plate (junctional folds of the sarcolemma) and sodium enters the cell. Binding of the neurotransmitter causes chemically gated sodium channels to open in the motor end plate (junctional folds of the sarcolemma) and sodium enters the cell. Binding causes potassium voltage-gated channels to open in the motor end plate (junctional folds of the sarcolemma) and potassium enters the cell. Binding causes chemically gated potassium channels to open in the motor end plate (junctional folds of the sarcolemma) and potassium enters the cell.

Binding of the neurotransmitter causes chemically gated sodium channels to open in the motor end plate (junctional folds of the sarcolemma) and sodium enters the cell.

The cross bridge cycle starts when _________. acetylcholine diffuses away from the synaptic cleft Ca2+ from the sarcoplasmic reticulum binds to tropomyosin Ca2+ from the sarcoplasmic reticulum binds to troponin ATP binds to troponin and is hydrolyzed to ADP and Pi Ca2+ is actively transported into the sarcoplasmic reticulum

Ca2+ from the sarcoplasmic reticulum binds to troponin

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 nuclei. Calcium ions are stored in the mitochondria. Calcium ions are stored in the sarcoplasmic reticulum. Calcium ions are stored in the transverse tubules.

Calcium ions are stored in the sarcoplasmic reticulum.

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

Calcium ions bind to troponin and change its shape.

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

Calcium ions travel through the transverse tubule.

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

Calcium release from the sarcoplasmic reticulum initiates the contraction.

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

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

How is delayed-onset muscle soreness (DOMS) different from muscle fatigue? Delayed-onset muscle soreness occurs a day or more after the physical exertion. There may be damage to the sarcolemma. Muscle performance is impaired. Delayed-onset muscle soreness involves pain.

Delayed-onset muscle soreness occurs a day or more after the physical exertion.

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. Excitation refers to the release of calcium ions from the sarcoplasmic reticulum. Excitation refers to the propagation of action potentials along the axon of a motor neuron. Excitation refers to the shape change that occurs in voltage-sensitive proteins in the sarcolemma.

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

What structure most directly stimulates a skeletal muscle fiber to contract? Voltage-gated calcium channels Synaptic cleft Motor neuron Acetylcholinesterase

Motor neuron

Which of the following statements is true concerning motor units? Movement of the eyeball requires fewer muscle fibers with less tension being produced. A small number of muscle fibers with increased tension is needed in large, gross movements. An increased number of motor neurons is needed in precise movements such as lifting a cup of coffee than in lifting a dumbbell. Lesser tension is required in lifting a dumbbell than in lifting a cup of coffee. A motor unit consists of all the muscle fibers it controls as well as the area of the spinal cord where it originates.

Movement of the eyeball requires fewer muscle fibers with less tension being produced.

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

Pyruvic acid is converted back to lactic acid.

Inadequate calcium in the neuromuscular junction would directly affect which of the following processes? Conduction of action potentials by the motor neuron Release of acetylcholine from the synaptic vesicles Breakdown of acetylcholine by acetylcholinesterase Depolarization of the junctional folds

Release of acetylcholine from the synaptic vesicles

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

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 myofibrils the sarcoplasmic reticulum myofilaments

T tubules

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

T tubules

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

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

Identify the incorrect statement about a single motor unit. Muscle fibers of one motor unit intermingle with the fibers of another motor unit. The more neurons involved, the more powerful the contraction. The smaller the number of muscle fibers, the more precise the movement. Fine motor skills depend on the development of small motor units. Some motor units include as many as 2000 muscle fibers.

The more neurons involved, the more powerful the contraction.

Which of the following statements is true? The neurotransmitter is stored in the presynaptic motor neuron. The acetylcholine (ACh) receptors are located on the myofibril. The sarcolemma is the presynaptic membrane. Acetylcholinesterase (AChE) is stored in vesicles within the presynaptic motor neuron.

The neurotransmitter is stored in the presynaptic motor neuron.

Why do the disease tetanus and the normal sustained muscle contraction called tetanus share the same name? They both eliminate the relaxation phase in the affected muscle fibers. They are both brought on by bacterial infections. They both enable muscle fibers to reach near maximum tension. All of the listed responses are correct.

They both eliminate the relaxation phase in the affected muscle fibers.

Which of the following is important to increasing efficiency in tension production? increasing the latent period a shortened relaxation phase increasing calcium reclamation lengthening the zone of overlap

a shortened relaxation phase

Which of the following situations could contribute to prolonged muscle contraction? limited availability of calcium ions cross-bridge formation being reduced infrequent neural stimulus acetylcholinesterase not being produced

acetylcholinesterase not being produced

A myosin head binds to which molecule to form a cross bridge? View Available Hint(s actin troponin tropomyosin

actin

Myosin molecules form cross-bridges when they attach to __________. actin troponin calcium tropomyosin

actin

Which of the following proteins contains the active site involved in cross-bridge formation? actin tropomyosin myosin troponin

actin

The most important factor in decreasing the intracellular concentration of calcium ion after contraction is active transport of calcium into the synaptic cleft. diffusion of calcium out of the cell. active transport of calcium across the sarcolemma. diffusion of calcium into the sarcoplasmic reticulum. active transport of calcium into the sarcoplasmic reticulum.

active transport of calcium into the sarcoplasmic reticulum.

What can the nervous system do to increase muscle tension? increase the number of active motor units recruit larger motor units increase stimulation frequency All of the listed responses can increase muscle tension.

all of the above

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

all of the above

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

arrival of an action potential

What causes the myosin head to disconnect from actin? binding of troponin binding of calcium hydrolysis of ATP binding of ATP

binding of ATP

The role of acetylcholinesterase is to bind to ligand gated sodium channels. transport acetylcholine across the synaptic cleft. activate acetylcholine. break down acetylcholine into acetate and choline components. release acetylcholine into the synaptic cleft.

break down acetylcholine into acetate and choline components.

The sarcoplasmic reticulum contains __________. myofilaments calcium troponin T tubules

calcium

Triads in skeletal muscle fibers function in __________. neuromuscular transmission relaxation calcium ion release calcium ion uptake

calcium ion release

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

detaching and resetting cross-bridges

Conduction of an action potential along the sarcolemma depends upon ___________. binding of acetylcholine to chemically gated channels release of calcium ions from the terminal cisterns shifting tropomyosin to uncover myosin binding sites diffusion of sodium ions through voltage-gated channels

diffusion of sodium ions through voltage-gated channels

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

elastic protein

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

exocytosis

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

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

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

fascicles

Muscles that move the eyeball have ________ fibers. slow fast circular intermediate All of the answers are correct.

fast

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

fast fibers

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

glycolysis

Which of the following allows muscles to return to their original shape during relaxation? opposing muscle contractions myosin binding elastic forces gravity gravity, opposing muscle contractions, and elastic forces

gravity, opposing muscle contractions, and elastic forces

A fascicle is a group of muscle fibers that are all part of the same motor unit. layer of connective tissue that separates muscle from skin. group of muscle fibers that are encased in the perimysium. collection of myofibrils in a muscle fiber. group of muscle fibers and motor neurons.

group of muscle fibers that are encased in the perimysium.

Cardiac muscles cells have a sarcolemma that is more permeable to calcium, which causes them to __________. pump calcium back into the sarcoplasmic reticulum faster have contractions that last longer than skeletal muscle fibers form more cross-bridges have faster contractions than skeletal muscle fibers

have contractions that last longer than skeletal muscle fibers

A weight-lifter strains to lift a heavy weight and there is no movement of the person's arms holding on to the weight. This type of contraction is called a(n) ________ contraction. concentric isometric treppe isotonic tetanus

isometric

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

made of a series of sarcomeres

Bacteria that cause tetanus release a neurotoxin. Which of the following components of the neuromuscular junction (NMJ) does this neurotoxin affect directly? motor neurons myofilaments epimysium sarcolemma

motor neurons

A single motor neuron together with all the muscle fibers it innervates is called a(n) motor unit. dermatome. end plate. end foot. myotome.

motor unit

Interactions between actin and myosin filaments of the sarcomere are responsible for muscle contraction. muscle fatigue. muscle relaxation. the striped appearance of skeletal muscle. the conduction of neural stimulation to the muscle fiber.

muscle contraction

During the recovery period following exercise, all of the following are true except the muscle actively produces ATP. heat is generated. oxygen is consumed at above the resting rate. lactic acid is removed from muscle cells. muscle fibers are unable to contract.

muscle fibers are unable to contract.

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

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? postural muscles of the back thigh muscles calf muscles muscles of the neck muscles that control the eyes

muscles that control the eyes

Thick filaments are made of the protein actin. titin. myosin. tropomyosin. nebulin.

myosin

Which of the following is involved in the power stroke? tropomyosin myofibrils myosin Z lines

myosin

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 increases tone in the muscle increases the muscle's excitability produces a strong, continuous state of contraction causes a strong contraction similar to a "charlie horse" cramp

reduces the muscle's ability for contraction

What causes the power stroke? binding of ATP calcium release of ADP and Pi hydrolysis of ATP

release of ADP and Pi

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 treppe. tetany. depolarization. oxygen debt. rigor mortis.

rigor mortis

The repeating unit of a skeletal muscle fiber is the myofibril. myofilament. sarcomere. sarcoplasmic reticulum. sarcolemma.

sarcomere

Z lines define the edges of which of the following? cross-bridges sarcomeres myosin myofibrils

sarcomeres

In response to an action potential along the transverse tubules, the __________ release(s) calcium ions into the sarcoplasm. sarcoplasmic reticulum sarcomere troponin molecules motor-end plate

sarcoplasmic reticulum

Since each myofibril is attached at either end of the muscle fiber, when sarcomeres shorten, the muscle fiber strengthens. weakens. pulls from the middle. lengthens. shortens.

shortens

How is acetylcholine (ACh) removed from the synaptic cleft? simple diffusion away from the synaptic cleft and endocytosis into the muscle fiber acetylcholinesterase (AChE; an enzyme) and endocytosis into the muscle fiber acetylcholinesterase (AChE; an enzyme) only simple diffusion away from the synaptic cleft and acetylcholinesterase (AChE; an enzyme)

simple diffusion away from the synaptic cleft and acetylcholinesterase (AChE; an enzyme)

The type of muscle fiber that is most resistant to fatigue is the ________ fiber. high-density fast intermediate slow anaerobic

slow

The narrow space between the synaptic terminal and the muscle fiber is the motor end plate. synaptic knob M line. synaptic cleft. motor unit.

synaptic cleft

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

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? T tubule cytosol sarcolemma terminal cisterns (cisternae) of the sarcoplasmic reticulum

terminal cisterns (cisternae) of the sarcoplasmic reticulum

Which of the following hormones directly stimulates growth of muscle tissue, leading to increased muscle mass? testosterone thyroid hormone epinephrine calcitonin parathyroid hormone

testosterone

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

the opening of ligand-gated cation channels

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

the sarcomere

Increased muscle fiber endurance can be produced by __________. a muscle fiber with a smaller diameter the amount of excitation-contraction coupling the length of the muscle fiber the type of activity performed

the type of activity performed

The soleus muscle is very red in color. Which of these statements about soleus muscle fibers is FALSE? They have a slow twitch speed. They are large in diameter. They are rich in myoglobin. They are slow to fatigue.

they are large in diameter

Myosin molecules form what part of the sarcomere? actin thin filament thick filament tropomyosin

thick filament