Chapter 9
Identify the structure where ATP is produced.
1
Which structure contains the motor end plate?
2
During anaerobic glycolysis
ATP is produced. pyruvic acid is produced. oxygen is not consumed. carbohydrate is metabolized.
Which structure in the figure corresponds to a single skeletal muscle cell?
C
Which of the following statements is false?
Cardiac muscle stimulation is neural.
What is thought to happen in a muscle during the response shown in graph (a)?
There is a gradual increase in the concentration of calcium ions in the sarcoplasm.
Eccentric contractions are more forceful than concentric contractions.
True
Peristalsis is characteristic of smooth muscle.
True
Heat energy produced from muscle contraction is released by the ________ system.
integumentary
All of the following are found in both skeletal and cardiac muscle fibers except __________.
intercalated disks
When contraction occurs,
the I bands get smaller. the width of the A band remains constant. the Z lines move closer together. the H bands get smaller.
The smallest contractile unit within skeletal muscle would correspond to the distance between which two points in the figure?
1 and 7
The region between which two points corresponds to the entire A (dark) band?
2 and 6
In which phase of the muscle twitch shown in the figure would the maximum amount of ATP be consumed by myosin head groups?
B
Which of the following is true about smooth muscle?
Certain smooth muscle cells can actually divide to increase their numbers.
A motor neuron and all the muscle cells that it stimulates are referred to as a motor end plate.
False
ATP is required to cause the power stroke in the myosin head.
False
The region of the sarcomere that always contains thin filaments is the
I band.
In a sarcomere, thick filaments are linked laterally by proteins of the
M line.
Based on what you know of the relationship between the thick and the thin filaments, what would happen if a disorder existed that caused a person to produce no tropomyosin?
The muscle tissues would never be able to relax.
Which protein is indicated by the letter A?
actin
Titin is a(n) __________.
elastic protein
The contraction of a muscle exerts a pull on a bone because
muscles are attached to bones by tendons.
The intercalated disk is a not site of __________.
neuromuscular transmission
Muscle tissue has all of the following properties except ________.
secretion
What is the most distinguishing characteristic of muscle tissue?
the ability to transform chemical energy into mechanical energy to move the body
Where is ATP consumed?
3 and 6
The following is a list of the events that occur during a muscle contraction.
3, 5, 1, 4, 6, 2.
Where are the myosin molecules located?
5
Which structure actively pumps calcium ions out of the sarcoplasm to produce relaxation?
6
Put the following structures in order from superficial to deep:
6, 2, 4, 5, 1, 3
Where would calcium ions be predominately found?
9
Aerobic metabolism normally provides ________ percent of the ATP demands of a resting muscle cell.
95
The molecular interaction described as a cross bridge involves the binding of which two proteins?
A and C
The region of the sarcomere containing the thick filaments is the
A band.
A toxin released by certain bacteria can block the release of neurotransmitters into a neuromuscular synapse. What would result from such a block?
A toxin released by certain bacteria can block the release of neurotransmitters into a neuromuscular synapse. What would result from such a block?
Which step precedes all of the other listed steps?
ACh is released by the motor neuron.
Approximately 80% of a muscle fiber's volume are the myofibrils. This characteristic reflects muscles ability to ________.
Approximately 80% of a muscle fiber's volume are the myofibrils. This characteristic reflects muscles ability to ________.
Which of the following corresponds to a single fascicle?
B
Which of the structures is surrounded by the connective tissue sheath known as the perimysium?
B
Which of the following interactions must occur first so that the others can take place?
B binds to troponin.
Which statement accurately describes the event indicated by B?
Binding of acetylcholine to a receptor triggers the opening of an ion channel.
In which phase in the figure would the net movement of Ca2+ into the sarcoplasmic reticulum (SR) be greatest?
C
Which protein functions as a motor protein that applies the power stroke during muscle contraction?
C
Which of the following is most directly required to initiate the coupling of myosin to actin?
Ca+
Which statement about excitation-contraction coupling is incorrect?
Calcium ion is released from the transverse tubule.
Which of these is true of cardiac muscle fibers?
Cardiac fibers have a single nucleus. Cardiac fibers branch. Cardiac fibers have a long twitch duration compared to skeletal fibers.
Curare is a poisonous plant extract. Curare molecules have a chemical structure like the neurotransmitter ACh. Curare can bind to the ACh receptor site on the chemically gated ion channels in the motor end plate. Even though curare will bind to the receptor site it will not open the ion channel and no ions will pass through. What do you think the symptoms of curare poisoning would look like?
Curare will only affect muscles with ACh receptors, paralyzing them.
Which statement about the microscopic anatomy of skeletal muscle fibers is true?
Each fiber has many nuclei. Tubular extensions of the sarcolemma penetrate the fiber transversely. Muscle fibers are continuous from tendon to tendon. Cross striations result from the lateral alignment of thick and thin filaments.
During isometric contraction, the energy used appears as movement.
False
Muscle contraction will always promote movement of body parts.
False
Once a motor neuron has fired, all the muscle fibers in a muscle contract.
False
The longer a muscle is when it starts contracting, the more tension it can generate in the contraction.
False
The area in the center of the A band that contains no thin filaments is the
H band.
Gary was injured in an automobile accident that severed the motor neurons innervating his quadriceps. Even though he has had extensive physical therapy, he is still suffering muscle atrophy. Why is the therapy not working?
In denervation (disuse) atrophy, fibrous connective tissue replaces the muscle tissue that was lost. When atrophy is complete, fibrous tissue cannot be reversed to muscle tissue.
Which of the following statements is NOT true regarding ATP production in muscles during periods of prolonged energy use, such as exercise?
In the absence of oxygen, creatine phosphate can drive aerobic respiration pathways for a few minutes.
If the cell could no longer produce ATP, what would be the effect on the sarcoplasmic reticulum?
It would be unable to concentrate Ca+ in the sarcoplasmic reticulum.
How would the loss of acetylcholinesterase from the motor end plate affect skeletal muscle?
It would cause spastic paralysis (muscles are contracted and unable to relax).
How would an elevated level of thyroid hormone in the body affect skeletal muscles?
It would stimulate energy use and heat production.
Which of the following statements is most accurate?
Muscle tension remains relatively constant during isotonic contraction.
Aaron arrived at the hospital with the following symptoms: drooping eyelids; fatigue and weakness of his muscles; and difficulty talking, breathing, and swallowing. What was his diagnosis?
Myasthenia gravis
A myosin molecule in the thick filaments can be considered a protein having a quaternary structural level. Which of the following best describes this structural level?
Myosin molecules consist of two heavy and two light polypeptide chains.
If a muscle fiber were to suddenly and permanently stop producing ATP the fiber would no longer be able to actively transport calcium out of the cytoplasm (sarcoplasm) and the intracellular calcium concentration would rise. Which of the following would you expect to happen?
Myosin would be able to bind to the exposed binding sites on thin filaments but it would not be able to detach.
Why is there partial relaxation in graph (c)?
Nerve stimulation frequency is below maximum.
If both motor neurons shown in this figure were to develop action potentials and stimulate muscle fibers, would all the muscle cells shown here contract?
No, because neurons in this figure do not innervate every muscle cell shown.
Cycling of myosin cross-bridges results in ___________.
Repeated cycling of cross-bridges causes all of these effects.
Which of the following statements is true?
Skeletal muscle cells are long and cylindrical with many nuclei.
Which of the following statements is FALSE?
Skeletal muscle cells use creatine phosphate instead of ATP to do work.
Which of the following statements best illustrates the fact that skeletal muscle is voluntary muscle?
Skeletal muscle fibers are innervated by somatic motor neurons.
Which of the following is true?
Skeletal muscle fibers contain sarcomeres; smooth muscle fibers do not.
Of the following items listed below, which is the best description for why skeletal muscle stores glycogen.
Skeletal muscle is a heavy consumer of energy.
Which of the following statements is (are) true regarding human muscles?
Slow fibers are abundant in the back muscles. Most have both slow and fast fibers. Eye muscles are composed entirely of fast fibers. Slow fibers are abundant in the calf muscles.
Which of the following is not characteristic of smooth muscle?
Smooth muscle connective tissue forms tendons and aponeuroses.
The contractile, or functional, unit of a muscle fiber is __________.
The contractile, or functional, unit of a muscle fiber is __________.
The nurse encourages the patient to do his own activities of daily living such as bathing, eating, dressing, and toileting activities. How do these activities promote physical conditioning?
The contraction of the muscles in these activities helps maintain the shape, size, and strength of muscles, as well as joint mobility.
One action potential in a motor neuron causes the full reaction in skeletal muscle, which is called a twitch. One twitch can generate max tension in a muscle. Are these statements true or false?
The first statement is true; the second statement is false.
What result would be expected if an additional stimulus, equal in intensity to the first, were to be applied to the muscle at the 60 millisecond (ms) time point?
The muscle would increase in tension to a level greater than that measured at the beginning of phase C.
The 100 meter dash is a quick and short run requiring explosive speed. On completion of the dash the runners will continue to breathe hard for several seconds to minutes even though they are no longer running. Which of the following is the best explanation for why this is so?
The runners' use of stored oxygen, glucose and creatine phosphate is being replenished and this requires a prolonged increase of oxygen intake.
The sliding filament model of contraction states that __________.
The sliding filament model of contraction states that __________.
Which of these statements about skeletal muscles is false?
Their fibers branch
The soleus muscle is very red in color. Which of these statements about soleus muscle fibers is false?
They are large in diameter.
Which of these is not a property of slow muscle fibers?
They are large in diameter.
Which of the following describes the cells of unitary smooth muscle?
They exhibit spontaneous action potentials.
What is the role of tropomyosin in skeletal muscles?
Tropomyosin serves as a contraction inhibitor by blocking the myosin binding sites on the actin molecules.
A contraction in which the muscle does not shorten but its tension increases is called isometric contraction.
True
A resting potential is caused by a difference in the concentration of certain ions inside and outside the cell.
True
Although there are no sarcomeres, smooth muscle still possesses thick and thin filaments.
True
An increase in the calcium ion level in the sarcoplasm starts the sliding of the thin filaments. When the level of calcium ions declines, sliding stops.
True
Cardiac muscle has a limited regenerative capacity.
True
Cells of unitary smooth muscle are found in the longitudinal and circular muscle layers of the intestine.
True
In the muscles of the limbs, the origin is usually the immobile muscle attachment.
True
Isometric contractions are important contractions that allow humans to hold their posture over time.
True
Muscle cells store more creatine phosphate than ATP resulting in the muscle having a reserve source of energy.
True
Muscle tone is the small amount of tautness or tension in the muscle due to weak, involuntary contractions of its motor units.
True
One of the important functions of skeletal muscle contraction is production of heat.
True
Smooth muscles relax when intracellular Ca2+ levels drop but may not cease contractions.
True
The effect of a neurotransmitter on the muscle cell membrane is to modify its ion permeability properties temporarily.
True
The force of muscle contraction is controlled by multiple motor unit summation or recruitment.
True
The thin filaments (actin) contain a polypeptide subunit G actin that bears active sites for myosin attachment.
True
When a muscle fiber contracts, the I bands diminish in size, the H zones disappear, and the A bands move closer together but do not diminish in length.
True
Which of the following are correctly paired?
Which of the following are correctly paired?
A fascicle is
a group of muscle fibers that are encased in the perimysium.
Most skeletal muscles contain ________.
a mixture of fiber types
A single motor neuron together with all the muscle fibers it innervates is called
a motor unit.
Sarcomere is best defined as ___________.
a repeating unit of striated muscle
What is the functional unit of a skeletal muscle called?
a sarcomere
A single muscle action potential will normally be followed by __________.
a single pulse of calcium ion release
Muscle tone is ________.
a state of sustained partial contraction
The skeletal muscle complex known as the triad consists of
a transverse tubule and two terminal cisternae.
The rapid rise and fall in force produced by a muscle fiber after a single action potential is
a twitch.
During neuromuscular transmission, the axon terminals release __________.
acetylcholine
Triggering of the muscle action potential occurs after
acetylcholine binds to chemically-gated channels in the end plate membrane.
Although all the anatomical parts of muscle work together to give it its characteristics, which of the following proteins listed below would be most associated with the characteristics of excitability?
acetylcholine receptors in the motor end plate
The cytoplasm of the neuromuscular terminal contains vesicles filled with molecules of the neurotransmitter
acetylcholine.
After nervous stimulation stops, what prevents ACh in the synaptic cleft from continuing to stimulate contraction?
acetylcholinesterase destroying the ACh
Which of the following are found in the structure labeled "3"?
actin tropomyosin titin myosin
The sliding filament model of contraction involves ________.
actin and myosin sliding past each other and partially overlapping
During muscle contraction, myosin cross bridges attach to which active sites?
actin filaments
The biochemical reaction that consumes the majority of a muscle's ATP is the __________.
actin myosin cross-bridge cycle
The most important factor in decreasing the intracellular concentration of calcium ion after contraction is
active transport of calcium into the sarcoplasmic reticulum.
Creatine phosphate
acts as an energy reserve in muscle tissue.
During the recovery period the body's need for oxygen is increased because
additional oxygen is required to restore energy reserves consumed during exercise.
A resting muscle generates most of its ATP by
aerobic metabolism of fatty acids.
Decreased blood flow to a muscle could result in all of the following, except
an increase in intracellular glycogen.
After heavy exercise, if energy reserves in a muscle are depleted, ________ occurs.
an oxygen debt
Muscles are attached to bones by tendons or __________.
aponeuroses
When comparing slow muscle fibers to fast muscle fibers, slow fibers
are rich in the red protein myoglobin. have much smaller fiber diameters. generate much less tension. take about three times as long to reach peak tension.
Identify the correct sequence of the following events. (a) Myosin generates a power stroke. (b) Ca+ binds to troponin. (c) ATP recharges the myosin head. (d) Troponin removes tropomyosin from G actin. (e) The sarcomere shortens. (f) Myosin binds to actin.
b, d, f, a, e, c
Active sites on the actin become available for binding after
calcium binds to troponin.
Triads in skeletal muscle fibers function in __________.
calcium ion release
What is released from the structure labeled "9"?
calcium ions
In response to action potentials arriving along the transverse tubules, the sarcoplasmic reticulum releases
calcium ions.
Smooth muscle contracts when calcium binds to __________ and activates __________.
calmodulin; myosin light chain kinase
In an isotonic contraction, the muscle ________.
changes in length and moves the "load"
A muscle producing its maximum tension is in __________.
complete tetanus
What is the contraction in graph (d) called?
complete tetanus
When a muscle is stimulated repeatedly at a high rate, the amount of tension gradually increases to a steady maximum tension. This is called
complete tetanus.
What physiological process occurs in the structure labeled "7"?
conduction of the action potential into the cell interior
Muscle tissue, one of the four basic tissue groups, consists chiefly of cells that are highly specialized for
contraction.
In rigor mortis
cross-bridge cycling is absent. muscles are inextensible. ATP is depleted. the myosin heads are attached to actin.
In a bedridden patient recovering from a badly fractured femur, disuse atrophy in the thigh muscles is caused by _________.
decreased synthesis of muscle proteins and/or increased breakdown of muscle proteins
Physical evidence that supports the sliding filament theory of muscle contraction includes
decreased width of the H band during contraction.
What event directly triggers the release of neurotransmitter shown in A?
diffusion of Ca2+ into the axon terminal
Which pathway for regenerating ATP is the most inefficient during 30 minutes of light to moderate exercise?
direct phosphorylation of ADP by creatine phosphate
A muscle that is lengthening while it produces tension is performing a(n) __________ contraction.
eccentric
Although all the anatomical parts of muscle work together to give it its characteristics, which of the following proteins listed below would be most associated with the characteristics of extensibility?
elastic (titin) filaments
Nerves and blood vessels that service a muscle fiber are located in the connective tissues of its
endomysium
The capillaries that wrap around each muscle fiber are located within the __________.
endomysium
Which of the following surrounds the individual muscle cell?
endomysium
The delicate connective tissue that surrounds the skeletal muscle fibers and ties adjacent muscle fibers together is the
endomysium.
What is the functional role of the T tubules?
enhance cellular communication during muscle contraction
The dense layer of connective tissue that surrounds an entire skeletal muscle is the
epimysium.
Muscle tissue can be stimulated by the nervous system. This is because of the membrane potential in the muscle cell. Cells with a membrane potential have what property?
excitability
Synaptic vesicles contain neurotransmitters that are released by ________ when the action potential arrives.
exocytosis
What cellular event is indicated by A?
exocytosis
The __________ type of muscle fiber has relatively few mitochondria.
fast
Large-diameter, densely packed myofibrils, large glycogen reserves, and few mitochondria are characteristics of
fast fibers.
Muscles that move the eyeball have
fast fibers.
Addition of more mitochondria to a muscle fiber will have the least effect on ________.
fast glycolytic fibers
Exhaustion of glycogen storage within a muscle fiber would have the biggest effect on ________.
fast glycolytic fibers
Addition of more myoglobin to a muscle fiber would have the largest effect on ________.
fast oxidative and slow oxidative fibers
Which of the following is not a function of smooth muscle tissue?
forcing blood from the heart into the major arteries
During the Cori cycle, in the liver
glucose is produced from lactic acid.
An anaerobic metabolic pathway that results in the production of two net ATPs per glucose plus two pyruvic acid molecules is ________.
glycolysis
Fast fibers
have low resistance to fatigue and have quick twitches.
Muscle fibers differ from "typical cells" in that muscle fibers
have many nuclei.
What is the function of the muscle cell feature indicated by the arrow? (arrow on top image)
houses the genetic material of the cell
Each skeletal muscle fiber contains ________ myofibrils.
hundreds to thousands
A muscle producing tension that peaks and falls at intermediate stimulus rates is said to be in
incomplete tetanus.
Which of these would lead to increased oxygen consumption?
increased conversion of lactic acid to glucose increased aerobic respiration by muscle cells increased muscle activity increased heat production
The strongest muscle contractions are normally achieved by ________.
increasing the stimulation up to the maximal stimulus
Myasthenia gravis is sometimes treated medically by a treatment that involves ________.
inhibiting the action of acetylcholinesterase
Which arrangement of the sarcomere gives rise to the structure (band or line) indicated by the arrow? (arrow pointing to m line)
is the point of connection for adjacent thick filaments
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/an ________ contraction.
isometric
When a muscle contraction develops tension but doesn't shorten the muscle, the contraction is called __________.
isometric
The type of contraction in which the muscle fibers do not shorten is called
isometric.
During vigorous exercise, there may be insufficient oxygen available to completely break down pyruvic acid for energy. As a result, the pyruvic acid is converted to ________.
lactic acid
Muscle fatigue occurs due to a buildup of __________ and __________ in pH.
lactic acid; decrease
Immediately following the arrival of the stimulus at the axon terminal of a motor neuron there is a short period called the ________ period during which the neurotransmitter is released by exocytosis, diffuses across the synaptic cleft, and binds to its receptors.
latent
Which of the following is a factor that affects the velocity and duration of muscle
load on the fiber
Which of the following factors influence the velocity and duration of muscle contraction?
load placed on the muscle
The muscle weakness of myasthenia gravis results from
loss of acetylcholine receptors in the end-plate membrane.
What is the function of the muscle cell feature indicated by the arrow? (arrow pointing to bottom image upper left of image)
making of ATP - the "power house" of the cell
Because skeletal muscle contractions demand large quantities of ATP, skeletal muscles have
many mitochondria and a rich blood supply.
Identify the structure labeled "1."
mitochondria
Cross bridge formation between myosin heads and actin molecules is caused by the elevation of calcium ion concentration in the cytosol. During rigor mortis, this elevation of calcium ion concentration in the cytosol is permanent because ________.
mitochondria stop producing ATP molecules required by the sarcoplasmic reticulum's calcium ion pumps
What level of structural organization do voltage-gated sodium channels in muscle sarcolemma represent?
molecule
When acetylcholine binds to receptors at the motor end plate, the end plate membrane becomes
more permeable to sodium ions.
During activities requiring aerobic endurance
most of the muscle's energy is produced in mitochondria.
What part of the sarcolemma contains acetylcholine receptors?
motor end plate
Receptors for acetylcholine are located on the
motor end plate.
Which of the following is the correct sequence of events for muscle contractions?
motor neuron action potential, neurotransmitter release, muscle cell action potential, release of calcium ions from SR, ATP-driven power stroke, sliding of myofilaments
Each neuron shown in this figure innervates a group of muscle fibers. What is the term for a group of muscle fibers innervated by a single neuron?
motor unit
Which of the following would be recruited later in muscle stimulation when contractile strength increases?
motor units with larger, less excitable neurons
Of the following muscle types, which has only one nucleus, no sarcomeres, and few gap junctions?
multi unit smooth muscle
During development embryonic cells will fuse to form muscle fibers. This will result in ________.
multinucleated muscle fibers that can extend as long as 30 centimeters
Interactions between actin and myosin filaments of the sarcomere are responsible for
muscle contraction.
Which term best identifies a muscle cell?
muscle fiber
During the recovery period following exercise, all of the following are true, except
muscle fibers are unable to contract.
In an isotonic contraction,
muscle tension exceeds the load and the muscle lifts the load.
In which of the following would the motor units have the fewest muscle fibers?
muscles that control the eyes
To produce a contraction similar to the one in graph (b), the muscle
must be stimulated again before it has relaxed from the previous stimulation.
Skeletal muscle fibers are formed from embryonic cells called
myoblasts.
The contractile units of skeletal muscles are ________.
myofibrils
The oxygen-binding protein found in muscle cells is ________.
myoglobin
Which protein is indicated by the letter E?
myosin
Which thick filament binds to actin once its active binding sites are exposed?
myosin
Cross-bridges are portions of
myosin molecules.
Each skeletal muscle fiber is controlled by a motor neuron at a single
neuromuscular junction.
Rigor mortis occurs because ________.
no ATP is available to release attached actin and myosin molecules
Hypothetically, if a muscle were stretched to the point where thick and thin filaments no longer overlapped, ________.
no muscle tension could be generated
Duchenne muscular dystrophy could theoretically be cured if a technique was developed that would _________.
none of the above
At peak levels of muscle exertion the mitochondria can supply
only about one-third of the energy required by the muscle.
Anaerobic glycolysis provides energy for muscle contraction when the supply of __________ is limited.
oxygen
What is the function of the muscle cell feature indicated by the arrows? (arrow on bottom image right corner of image)
part of coupling the action potential to contraction
A thin layer of connective tissue that surrounds a muscle fascicle is called the __________.
perimysium
Resting smooth muscle can be stretched without developing much tension because of its __________.
plasticity
The ability of smooth muscle to function over a wide range of lengths is called
plasticity
Which of the following is a recognized function of skeletal muscle?
produce movement maintain body temperature guard body entrances and exits maintain posture
What is the primary function of wave summation?
produce smooth, continuous muscle contraction
What is the function of the filaments found in ranges 1-2 and 6-7 but no other ranges?
protection from overstretching
Which of the following best describes the term titin?
protein that accounts for elasticity of resting muscle
Skeletal muscle does each of these except __________.
pump blood
Which of these is not a function of smooth muscle?
pushing blood into the arteries
To increase muscle tension, the nervous system can __________.
recruit larger motor units increase the number of active motor units increase the stimulation frequency
If both of the neurons in the figure were activated, more muscle fibers would contract than if either neuron alone were active. This mechanism for control of the force of muscle contraction is known as __________.
recruitment
Suppose that 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?
recruitment
The increase in muscle tension that is produced by increasing the number of active motor units is called
recruitment.
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
When a muscle is unable to respond to stimuli temporarily, it is in which of the following periods?
refractory period
Excitation-contraction coupling includes all EXCEPT which of the following events?
release of acetylcholine from axon terminals at the neuromuscular junction
Fast muscle fibers can adapt to aerobic metabolism by generating more mitochondria in response to
repeated, exhaustive stimulation.
Which of the following best describes the term sarcomere?
repeating unit of striated myofibrils
After death, muscle fibers run out of ATP and calcium begins to leak from the sarcoplasmic reticulum into the sarcoplasm. This results in a condition known as
rigor mortis.
Slow oxidative muscle fibers are best suited for __________.
running a marathon
The action potential in skeletal muscle fibers is generated by the __________.
sarcolemma
The plasma membrane of a skeletal muscle fiber is called the
sarcolemma.
The __________ shorten(s) during muscle contraction
sarcomere
The repeating unit of a skeletal muscle fiber is the
sarcomere.
In response to an action potential along the transverse tubules, the __________ release(s) calcium ions into the sarcoplasm.
sarcoplasmic reticulum
What structure in skeletal muscle cells functions in calcium storage?
sarcoplasmic reticulum
The series of membranous channels that surround each myofibril is the
sarcoplasmic reticulum.
Which of the following is NOT a normal function of muscle tissue?
secreting hormones
Since each myofibril is attached at either end of the muscle fiber, when sarcomeres shorten, the muscle fiber
shortens.
Which type of muscle requires voluntary nervous stimulation for activation?
skeletal
Which type of muscle tissue has the greatest effect on the body's heat production?
skeletal
The type of muscle fiber that is most resistant to fatigue is the ________ fiber.
slow
Which type of muscle fibers are best adapted for prolonged contraction such as standing all day?
slow fibers
If given the exact same amount of ATP, which of the three fiber types would be able to contract for the longest amount of time?
slow oxidative fibers
Reduction in blood flow to a muscle fiber would have the greatest effect on ________.
slow oxidative fibers
Which muscle-fiber type is best suited for endurance activities, such as long-distance jogging?
slow oxidative fibers
Which muscle cells have the greatest ability to regenerate?
smooth
Oxygen starved tissues can release chemical signals into the blood that can change the diameter of nearby blood vessels delivering oxygen and nutrients to the tissues. In doing so the blood vessels will respond through vasodilation (widening of the vessel). Which muscle type is responsible for this vasodilation?
smooth muscle
Which of the following best describes the term sarcoplasmic reticulum?
storage and release site for calcium ions
What is the function of the muscle cell feature indicated by the arrow?
storage of calcium
Myoglobin ________.
stores oxygen in muscle cells
Creatine phosphate functions in the muscle cell by ________.
storing energy that will be transferred to ADP to resynthesize ATP
What feature of smooth muscle allows it to stretch without immediately resulting in a strong contraction?
stress-relaxation response
The narrow space between the synaptic terminal and the muscle fiber is the
synaptic cleft.
The connective tissue that covers structure A is continuous with which of the following?
tendon
At each end of the muscle, the collagen fibers of the epimysium, and each perimysium and endomysium, come together to form a
tendon.
The bundle of collagen fibers at the end of a skeletal muscle that attaches the muscle to bone is called a(n)
tendon.
Which of the following hormones directly stimulates growth of muscle tissue, leading to increased muscle mass?
testosterone
When a sarcomere contracts and thin filaments move over thick filaments you would expect to see ________.
the I bands to appear smaller
The advantage of having many nuclei in a skeletal muscle fiber is
the ability to produce large amounts of the muscle proteins needed for growth and repair.
The force of a muscle contraction is NOT affected by __________.
the amount of ATP stored in the muscle cells
Which arrangement of the sarcomere gives rise to the structure (band or line) indicated by the arrow? (arrow pointing to z line)
the boundary between adjacent sarcomeres
What does excess postexercise oxygen consumption represent?
the difference between the amount of oxygen needed for totally aerobic muscle activity and the amount actually used
Which of the following acts as an ATPase during the contraction cycle of muscle?
the head portion of the myosin molecule
Which of the following regions best identifies where myosin would have maximum cross-bridge access to actin?
the region between 2 and 3
Which arrangement of the sarcomere gives rise to the structure (band or line) indicated by the arrow?
the region of the resting sarcomere that only contains thick filaments
Which arrangement of the sarcomere gives rise to the structure (band or line) indicated by the arrow? (arrow pointing to the l band)
the region of the sarcomere that contains only thin filaments
Which organelle can chemically regulate the shortening of the muscle?
the sarcoplasmic reticulum
The mechanism of contraction in smooth muscle is different from skeletal muscle in that ________.
the site of calcium regulation differs
When a skeletal muscle fiber contracts,
the zones of overlap get larger. the H bands and I bands get smaller. the width of the A band remains constant. the Z lines get closer together.
Smooth muscle is characterized by all of the following except ________.
there are more thick filaments than thin filaments
Although all the anatomical parts of muscle work together to give it it's characteristics, which of the following proteins listed below would be most associated with the characteristics of contractility?
thick (myosin) filaments
Which of the following become connected by myosin cross-bridges during muscle contraction?
thin filaments and thick filaments
Which of the following best describes the term Z line?
thin filaments are anchored here
A potential benefit of recruiting slow oxidative fibers for contraction before recruiting fast oxidative and fast glycolytic fibers might be ________.
this will help to allow for fine control with delicate contractile force with a small stimulus
An enzyme known as acetylcholinesterase is present in the synaptic cleft. What is its role?
to break down acetylcholine
The muscle action potential penetrates into a fiber along the __________.
transverse tubules
The action potential is conducted into a skeletal muscle fiber by
transverse tubules.
What is the contraction in graph (a) called?
treppe
At rest, active sites on the actin are blocked by
tropomyosin molecules.
When calcium ion binds to troponin,
tropomyosin moves into the groove between the helical actin strands.
Which component of a thin filament binds to calcium once the calcium ion is released from the sarcoplasmic reticulum?
troponin
The thin filaments of striated muscle are made primarily of which protein(s)?
troponin tropomyosin actin nebulin
At rest, the tropomyosin molecule is held in place by
troponin molecules.
The interaction between which protein and ion initiates contraction of skeletal muscle?
troponin; calcium ions
Each thin filament consists of
two actin protein strands coiled helically around each other.
Which type of muscle is found in the wall of hollow organs?
unitary smooth muscle
Muscular force can be adjusted to match different loads by
varying the frequency of action potentials in motor neurons. recruiting larger motor units. involving more muscle fibers in the contraction. recruiting more motor units.
If a second stimulus arrives before the relaxation phase has ended, a second, more powerful contraction occurs. This is called
wave summation.
Myasthenia gravis is a disease that is believed to be caused by autoimmune disorder, resulting in the loss of ACh receptors at the motor end plate of muscle fibers. Which of the following is likely to be a symptom of myasthenia gravis?
weakness of muscle
In a sarcomere, cross-bridge attachment occurs specifically in the
zone of overlap.