ch 10

Put the following structures in order from superficial to deep. 1. muscle fiber 2. perimysium 3. myofibril 4. fascicle 5. endomysium 6. epimysium 2, 3, 1, 4, 6, 5 6, 2, 5, 4, 1, 3 6, 2, 4, 5, 1, 3 1, 3, 5, 6, 4, 2 1, 5, 4, 3, 2, 6

6, 2, 4, 5, 1, 3

Aerobic metabolism normally provides ________ percent of the ATP demands of a resting muscle cell. ANSWER: 25 95 70 50 100

95

The region of the sarcomere containing the thick filaments is the I band. M line. A band. Z line. H band.

A band

The cross bridge cycle is a series of molecular events that occur after excitation of the sarcolemma. What is a cross bridge? ANSWER: A myosin head bound to actin Troponin bound to tropomyosin ATP bound to a myosin head 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? ANSWER: Voltage-gated sodium channels. A series of proteins that control calcium release. Myosin cross-bridge binding sites. Potassium leak channels.

A series of proteins that control calcium release.

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

ACh

Which of the following is/are mechanism(s) to end neural transmission at the neuromuscular junction? ACh diffuses away from the synaptic cleft. ACh is taken up by the axon terminal via endocytosis. ACh is broken down into acetic acid and choline by the enzyme acetylcholinesterase (AChE). ACh binds to ACh receptors

ACh diffuses away from the synaptic cleft. ACh is broken down into acetic acid and choline by the enzyme acetylcholinesterase (AChE).

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

ACh is released at the synapse

The post-synaptic reaction on the sarcolemma is short in duration. Which of the following explanations describes why the reaction of the sarcolemma is short in duration? AChE acts to breakdown the ACh in the synaptic cleft. The ACh receptors respond only for a short period of time. ACh diffuses out of the synaptic cleft. Muscle tissue has a smaller membrane potential than nervous tissue. ACh diffuses across the synaptic cleft toward the sarcolemma.

AChE acts to breakdown the ACh in the synaptic cleft. ACh diffuses out of the synaptic cleft.

Cross bridge detachment is caused by ________ binding to the myosin head. ANSWER: acetylcholinesterase ATP magnesium calcium acetylcholine

ATP

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? ANSWER: acetylcholine acetylcholinesterase calcium ATP

ATP

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

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

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? 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. 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.

Tamara's muscle weakness and fatigue becomes progressively worse over the course of the day. This is a hallmark sign of myasthenia gravis, an autoimmune disorder that affects the ability of a motor neuron to communicate with a muscle fiber. What synaptic events must happen first for excitation to occur? ANSWER: Acetylcholine is released from the axon terminal and diffuses across the synapse to bind to a receptor in the surface of the motor end plate. Sodium ions from the extracellular fluid diffuse into the cytosol of the muscle fiber, triggering the generation of an action potential in the sarcolemma. Calcium binds to tropomyosin, shifting it from the active site on actin, allowing cross bridge formation to occur as myosin binds to the active site. The action potential travels down the T tubules in the sarcolemma and triggers the release of calcium ions from the sarcoplasmic reticulum.

Acetylcholine is released from the axon terminal and diffuses across the synapse to bind to a receptor in the surface of the motor end plate.

The injection that dramatically improved Tamara's symptoms was Tensilon, an acetylcholinesterase inhibitor. What is acetylcholinesterase, and why was this injection effective in relieving Tamara's symptoms? ANSWER: Acetylcholinesterase is an enzyme that degrades the ACh receptors. When acetylcholinesterase is inhibited, there are more receptors available for acetylcholine to bind, and muscle function improves. Acetylcholinesterase is an acetylcholine antagonist that binds to motor end plate receptors and decreases the permeability of the sarcolemma to sodium. Inhibiting acetylcholinesterase increases the influx of sodium, leading to the generation of action potentials and an improvement in muscle function. Acetylcholinesterase is the enzyme that clears acetylcholine from the synapse. Inhibiting this enzyme will enable acetylcholine to be available for a longer period to bind to receptors. Acetylcholinesterase is a regulatory enzyme that inhibits the ACh receptors on the motor end plate. Inhibiting acetylcholinesterase improves muscle function because the ACh receptors are temporarily more active.

Acetylcholinesterase is the enzyme that clears acetylcholine from the synapse. Inhibiting this enzyme will enable acetylcholine to be available for a longer period to bind to receptors.

How is acetylcholine (ACh) removed from the synaptic cleft? ANSWER: acetylcholinesterase (AChE; an enzyme) a reuptake pump on the axon terminal diffusion away from the synaptic cleft All of the above.

All of the above

In rigor mortis ANSWER: ATP is depleted. the myosin heads are attached to actin. calcium ions keep binding to troponin. sustained contractions occur. All of the answers are correct.

All of the answers are correct

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

All of the answers are correct.

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

All of the answers are correct.

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

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

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

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

Calcium ions are stored in the sarcoplasmic reticulum.

What specific event triggers the uncovering of the myosin binding site on actin? ANSWER: Calcium ions bind to troponin and change its shape. Calcium ions bind to tropomyosin and change its shape. Sodium 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 troponin and change its shape

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

Calcium release from the sarcoplasmic reticulum initiates the contraction.

When does cross bridge cycling end? ANSWER: Cross bridge cycling ends when ATP binds to the myosin head. 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.

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? ANSWER: Muscle performance is impaired. There may be damage to the sarcolemma. Delayed-onset muscle soreness involves pain. Delayed-onset muscle soreness occurs a day or more after the physical exertion.

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? ANSWER: 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. Excitation refers to the propagation of action potentials along the axon of a motor neuron. Excitation refers to the release of calcium ions from the sarcoplasmic reticulum.

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

The area in the center of the A band that contains no thin filaments is the zone of overlap. M line. H band. I band. Z line.

H band

The region of the sarcomere that always contains thin filaments is the Z line. A band. I band. M line. H band.

I band

Myasthenia gravis is an autoimmune disorder that results in the production of antibodies that either block or cause the destruction of the ACh receptor. Why do you think that Tamara's symptoms become worse as the day progresses? ANSWER: In the morning, the reserves of ATP are larger, allowing for sufficient acetylcholine release to overcome the unresponsive receptors. However, as the day progresses and stores of ATP become depleted, muscle function becomes progressively worse. In the morning, the neuronal reserves of acetylcholine are larger, allowing for sufficient neurotransmitter release and resulting in effective muscle signaling. As the day progresses and the stores of acetylcholine become depleted, muscle function becomes progressively worse. As the muscle becomes fatigued over the course of the day's activities, the receptors bind less acetylcholine, which results in smaller and smaller action potentials being generated. Smaller action potentials mean weaker contractions, as seen by the increasing muscle weakness. In myasthenia gravis the ACh receptors have a hyper affinity to acetylcholine. After muscle activity, fatigue and weakness occur as fewer unbound receptors are available to bind acetylcholine.

In the morning, the neuronal reserves of acetylcholine are larger, allowing for sufficient neurotransmitter release and resulting in effective muscle signaling. As the day progresses and the stores of acetylcholine become depleted, muscle function becomes progressively worse.

How would the loss of acetylcholinesterase from the motor end plate affect skeletal muscle? ANSWER: It would cause muscles to stay contracted. It would cause muscles to stay relaxed. It would have little effect on skeletal muscles. It would make the muscles less excitable. It would produce muscle weakness.

It would cause muscles to stay contracted.

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

Krebs cycle and oxidative phosphorylation

In a sarcomere, the central portion of thick filaments are linked laterally by proteins of the I band. M line. H band. Z line. A band.

M line

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

Pyruvic acid is converted back to lactic acid.

Which of the following statements is false? ANSWER: Skeletal muscle contractions may be summated. Cardiocytes are interconnected through intercalated discs. Cardiac muscle has a striated appearance. Skeletal muscle and cardiac muscle stimulation is neural. Cardiac muscle contractions cannot be summated.

Skeletal muscle and cardiac muscle stimulation is neural.

Calcium entry into the axon terminal triggers which of the following events? ANSWER: 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 __________. ANSWER: myofilaments the sarcoplasmic reticulum T tubules myofibrils

T tubules

How does the myosin head obtain the energy required for activation? ANSWER: The energy comes from the hydrolysis of ATP. The energy comes from the hydrolysis of GTP. The energy comes from the direct phosphorylation of ADP by creatine phosphate. The energy comes from oxidative phophorylation.

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. 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 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. Potassium ions diffuse inward 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.

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? ANSWER: The muscles would contract because of increased action potential generation in the sarcolemma. The muscles would contract because of calcium binding to troponin. The muscles would contract because of increased nerve stimulation. The muscles would relax because of calcium being pumped back into the sarcoplasmic reticulum.

The muscles would contract because of calcium binding to troponin.

What happens immediately after the myosin head binds to the active site on actin? ANSWER: The myosin head detaches from the active site on actin. ATP binds to the myosin head. Tropomyosin moves away from the active site on actin. The myosin head pivots, moving the actin strand.

The myosin head pivots, moving the actin strand

Which of the following statements is true? The sarcolemma is the presynaptic membrane. Acetylcholinesterase (AChE) is stored in vesicles within the presynaptic motor neuron. The acetylcholine (ACh) receptors are located on the myofibril membrane. The neurotransmitter is stored in 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? ANSWER: They are both brought on by bacterial infections. They both enable muscle fibers to reach near maximum tension. They both eliminate the relaxation phase in the affected muscle fibers. All of the above.

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

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

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

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

a shortened relaxation phase

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

a transverse tubule and two terminal cisternae

During neuromuscular transmission, the axon terminals release __________. ANSWER: acetylcholinesterase calcium ions sodium ions acetylcholine

acetylcholine

The cytoplasm of the neuromuscular terminal contains vesicles filled with molecules of the neurotransmitter ANSWER: adrenaline. acetylcholine. norepinephrine. antidiuretic hormone. epinephrine.

acetylcholine

Triggering of the muscle action potential occurs after ANSWER: acetylcholinesterase is released from synaptic vesicles into the synaptic cleft. calcium ion binds to channels on the motor end plate. the action potential jumps across the neuromuscular junction. acetylcholine binds to chemically-gated channels in the motor end plate. Any of these can produce an action potential in the muscle cell.

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

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

actin

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

actin

Thin filaments are mostly made of the protein ANSWER: nebulin. titin. tropomyosin. actin. myosin.

actin

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

actin

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

active transport of calcium into the sarcoplasmic reticulum.

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

acts as an energy reserve in muscle tissue.

During the recovery period the body's need for oxygen is increased because ANSWER: the muscles produce much less ATP. additional oxygen is required to restore energy reserves. muscle cells are producing ATP anaerobically. the liver requires more oxygen to produce lactic acid. creatine phosphate stimulates mitochondrial activity.

additional oxygen is required to restore energy reserves.

A resting muscle generates most of its ATP by ANSWER: the tricarboxylic acid cycle. glycogenolysis. anaerobic respiration. hydrolysis of creatine phosphate. aerobic metabolism of fatty acids.

aerobic metabolism of fatty acids.

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

an action potential in the neuron

Decreased blood flow to a muscle could result in all of the following except ANSWER: an oxygen debt. an increase in intracellular lactic acid. a shift to anaerobic glycolysis. an increase in intracellular glycogen. muscle fatigue.

an increase in intracellular glycogen.

After heavy exercise, if energy reserves in a muscle are depleted, ________ occurs. ANSWER: paralysis atrophy treppe an oxygen debt tetanus

an oxygen debt

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

arrival of an action potential

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

binding of ATP

The sarcoplasmic reticulum contains __________. ANSWER: troponin myofilaments calcium T tubules

calcium

Active sites on the actin become available for binding after ANSWER: actin binds to troponin. calcium binds to tropomyosin. myosin binds to troponin. troponin binds to tropomyosin. calcium binds to troponin.

calcium binds to troponin

In response to action potentials arriving along the transverse tubules, the sarcoplasmic reticulum releases ANSWER: sodium ions. acetylcholine. potassium ions. hydrogen ions. calcium ions.

calcium ions

Which of the following is most directly responsible for the coupling of excitation to contraction of skeletal muscle fibers? ANSWER: Calcium ions. Action potentials. Acetylcholine. Sodium ions.

calcium ions

Smooth muscle contracts when calcium binds to __________ and activates __________. ANSWER: calmodulin; myosin light chain kinase troponin; myosin light chain kinase calmodulin; troponin troponin; tropomyosin

calmodulin; myosin light chain kinase

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

contraction

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

decreased pH

Physical evidence that supports the sliding filament theory of muscle contraction includes ANSWER: the I band + H band distance is constant during contraction. increased width of the I band during contraction. decreased width of the A band during contraction. decreased width of the H band during contraction. constant distance between Z lines during contraction.

decreased width of the H band during contraction

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

dehydration synthesis

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

detaching and resetting cross-bridges

The dense layer of connective tissue that surrounds an entire skeletal muscle is the epimysium. endomysium. perimysium. tendon. fascicle.

epimysium

What means of membrane transport is used to release the neurotransmitter into the synaptic cleft? ANSWER: 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 brain or spinal cord to the sarcolemma of a skeletal muscle fiber extend from the 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

Activities involving eccentric contractions more commonly lead to delayed-onset muscle soreness than concentric or isometric contractions. Which of the following activities is thus a candidate for delayed-onset muscle soreness? ANSWER: carrying a bowling ball pushing against the wall in the gym flexion of the biceps brachii extension of the biceps brachii

extension of the biceps brachii

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

fasciles

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

fast

Which of the following is not a function of smooth muscle tissue? ANSWER: altering the diameter of the respiratory passageways elevating hairs on the arm forcing urine out of the urinary tract moving food materials along the digestive tract forcing blood from the heart into the major arteries

forcing blood from the heart into the major arteries

In the liver, during the Cori cycle, ANSWER: lactic acid is shuffled to muscle cells. glucose is released from glycogen. glucose is produced from lactic acid. lactic acid is produced from glucose. lactic acid is produced from pyruvic acid.

glucose is produced from lactic acid.

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

glycolysis

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

group of muscle fibers encased in the perimysium

Fast fibers ANSWER: rely on aerobic metabolism. have low resistance to fatigue and quick twitches. have twitches with a very brief contraction phase. have low resistance to fatigue. have many mitochondria.

have low resistance to fatigue and quick twitches.

A muscle producing almost peak tension during rapid cycles of contraction and relaxation is said to be in ANSWER: treppe. incomplete tetanus. wave summation. complete tetanus. recruitment.

incomplete tetanus.

Which of the following would not lead to increased oxygen consumption? ANSWER: increased heat production increased muscle activity increased anaerobic respiration by muscle cells increased conversion of lactic acid to glucose All of the answers are correct; none would lead to increased oxygen consumption.

increased anaerobic respiration by muscle cells

Heat energy gained from muscle contraction is released by the ________ system. ANSWER: cardiovascular urinary respiratory endocrine integumentary

integumentary

The type of contraction in which the muscle fibers do not shorten is called ANSWER: isometric. concentric. isotonic. treppe. tetany.

isometric

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

loss of acetylcholine receptors in the end-plate membrane.

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

made of a series of sarcomeres

When acetylcholine binds to receptors at the motor end plate, the sarcolemma becomes ANSWER: more permeable to calcium ions. more permeable to sodium ions. less permeable to potassium and sodium ions. less permeable to potassium ions. less permeable to sodium ions.

more permeable to sodium ions.

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

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

Receptors for acetylcholine are located on the ANSWER: motor end plate. synaptic cleft. transverse tubule. sarcomere. synaptic knob.

motor end plate

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

motor neurons

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

motor unit

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

muscle contraction

The neuromuscular junction is a connection between a neuron and a __________. ANSWER: muscle fiber myofibril vesicle synaptic terminal

muscle fiber

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

muscle fibers are unable to contract.

In an isotonic contraction, ANSWER: muscle tension exceeds the load and the muscle lifts the load. the peak tension is less than the load. postural muscles stabilize the vertebrae. tension rises and falls but the muscle length is constant. 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? ANSWER: postural muscles of the back muscles that control the eyes thigh muscles muscles of the neck calf muscles

muscles that control the eyes

Skeletal muscle fibers are formed from embryonic cells called myoblasts. fascicles. myofibrils. myomeres. sarcomeres.

myoblasts

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

myosin

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

myosin

What area of the thick filament binds to actin once its active binding sites are exposed? ANSWER: myosin cross-bridge (head) tropomyosin hinge troponin

myosin cross-bridge (head)

Cross-bridges are portions of calcium ions. troponin molecules. actin molecules. tropomyosin molecules. myosin molecules.

myosin molecules

Each skeletal muscle fiber is controlled by a motor neuron at a single ANSWER: sarcomere. neuromuscular junction. transverse tubule. synaptic knob. synaptic cleft.

neuromuscular junction

Acetylcholine receptors are primarily located __________. ANSWER: on the synaptic terminal on the motor end plate inside vesicles inside the muscle fiber

on the motor end plate

At peak levels of muscle exertion the mitochondria can supply ANSWER: all of the energy required by the muscle. only about 10 percent of the energy required by the muscle. 80 percent of the energy required by the muscle. more than half of the energy required by the muscle. only about one-third of the energy required by the muscle.

only about one-third of the energy required by the muscle.

The ability of smooth muscle to function over a wide range of lengths is called ANSWER: extensibility. elasticity. plasticity. variability. contractility.

plasticity

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

protein that accounts for elasticity of resting muscle

Skeletal muscle does each of these EXCEPT __________. pump blood store nutrients maintain posture produce movement

pump blood

You try to pick up an object and discover that it is much heavier than you expected. Which process must occur in the muscle to increase tension so you can pick up the object? ANSWER: treppe isotonic contraction recruitment wave summation complete tetanus

recruitment

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

release of ADP and Pi

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

remove acetylcholine from the synaptic cleft

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

sacromere

The plasma membrane of a skeletal muscle fiber is called the sarcoplasm. sarcoplasmic reticulum. sarcomere. sarcolemma. sarcosome.

sarcolemma

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

sarcomeres

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

sarcoplasmic reticulum

Which organelle completely surrounds each myofibril inside a muscle fiber? ANSWER: calcium fascicle sarcoplasmic reticulum nucleus

sarcoplasmic reticulum

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

skeletal

The structural theory that explains how a muscle fiber contracts is called the ________ theory. ANSWER: neuromuscular action-myosin interaction excitation-contraction coupling sliding filament muscle contraction

sliding filament

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

slow

Which of the following types of muscle fibers are best adapted for prolonged contraction such as standing all day? ANSWER: uninucleated fibers fast fibers slow fibers striated fibers intermediate fibers

slow fibers

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

storage and release site for calcium ions

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

synaptic cleft

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

synaptic terminal

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

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? ANSWER: sarcolemma T tubule cytosol terminal cisternae of the sarcoplasmic reticulum

terminal cisternae of the sarcoplasmic reticulum

A muscle produces its highest tension when in complete ANSWER: wave summation. aerobic metabolism. tetanus. recovery. treppe.

tetanus

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

the generation of an action potential in the sarcolemma

Which of the following acts as an ATPase during the contraction cycle of muscle? ANSWER: the head portion of the myosin molecule actin molecules the tail portion of the myosin molecule tropomyosin molecules troponin molecules

the head portion of the myosin molecule

An action potential in the muscle fiber causes __________. ANSWER: acetylcholine to bind to receptors on the motor end plate the muscle fiber to contract the release of acetylcholine into the synaptic cleft acetylcholinesterase to break down acetylcholine

the muscle fiber to contract

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

the opening of ligand-gated cation channels

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

the sarcomere

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

the space between the synaptic terminal and the motor end plate

Which of these statements about skeletal muscles is FALSE? They store nutrient reserves. They pull on tendons. They support soft tissues. Their fibers branch.

their fibers branch

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

thick filament

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

through calcium release from the sarcoplasmic reticulum

All of the following proteins are part of the thin filaments except ANSWER: actin. troponin. titin. tropomyosin. None of the answers is correct; there are no exceptions.

titin

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

transverse or t tubules

The action potential is conducted into a skeletal muscle fiber by ANSWER: sarcoplasmic reticulum. motor end plates. triads. neuromuscular junctions. transverse tubules.

transverse tubules

T tubules and the terminal cisternae are clustered into structures called __________. ANSWER: sarcomeres triads fascicles myofibrils

triads

When the sarcomere is at rest, what is covering the active sites on actin? ANSWER: tropomyosin troponin myosin cross-bridges

tropomyosin

At rest, active sites on the actin are blocked by myosin molecules. ATP molecules. troponin molecules. tropomyosin molecules. calcium ions.

tropomyosin molecules

When calcium ion binds to troponin, ANSWER: actin heads will bind to myosin. active sites on the myosin are exposed. tropomyosin rolls away from the active site. myosin shortens. muscle relaxation occurs.

tropomyosin rolls away from the active site.

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

tropomyosin shifting position

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

troponin

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

troponin

What component of the thin filament binds to calcium once calcium is released from the terminal cisternae of the sarcoplasmic reticulum? ANSWER: actin myosin tropomyosin troponin

troponin

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

troponin

A single contraction-relaxation cycle in a muscle fiber produces a(n) ANSWER: tetanic contraction. action potential. motor unit. cramp. twitch.

twitch

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

two actin protein strands coiled helically around each other

Inside a neuron, acetylcholine is contained within __________. ANSWER: vesicles the motor end plate the synaptic cleft acetylcholine receptors

vesicles

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

voltage-gated calcium channels

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

white fast twitch fibers