Chapter 10 Flashcards
1
Q
Which type of muscle tissue has the greatest effect on the body’s heat production?
skeletal
cardiac
smooth
All of these muscle types have about the same effect on the body’s heat production.
A
skeletal
2
Q
Muscle tissue, one of the four basic tissue groups, consists chiefly of cells that are highly specialized for
contraction.
conduction.
cushioning.
secretion.
peristalsis.
A
contraction
3
Q
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.
A
All of the answers are correct.
4
Q
The capillaries that wrap around each muscle fiber are located within the \_\_\_\_\_\_\_\_\_\_. sarcolemma epimysium perimysium endomysium
A
endomysium
5
Q
Muscles are attached to bones by tendons or \_\_\_\_\_\_\_\_\_\_.
perimysium
superficial fascia
ligaments
aponeuroses
A
aponeuroses
6
Q
A thin layer of connective tissue that surrounds a muscle fascicle is called the \_\_\_\_\_\_\_\_\_\_. epimysium tendon endomysium perimysium
A
perimysium
7
Q
At each end of the muscle, the collagen fibers of the epimysium, and each perimysium and endomysium, come together to form a
ligament.
tenosynovium.
sheath.
tendon.
satellite cell.
A
tendon.
8
Q
The dense layer of connective tissue that surrounds an entire skeletal muscle is the tendon. fascicle. perimysium. endomysium. epimysium.
A
epimysium.
9
Q
The bundle of collagen fibers at the end of a skeletal muscle that attaches the muscle to bone is called a(n) fascicle. epimysium. ligament. tendon. myofibril.
A
tendon.
10
Q
What is the function of the sarcoplasmic reticulum?
storage of calcium
houses the genetic material of the cell
making of ATP - the “power house” of the cell
part of coupling the action potential to contraction
A
storage of calcium
11
Q
What is the function of the nuclei?
storage of calcium
houses the genetic material of the cell
making of ATP - the “power house” of the cell
part of coupling the action potential to contraction
A
houses the genetic material of the cell
12
Q
What is the function of T tubules?
storage of calcium
houses the genetic material of the cell
making of ATP - the “power house” of the cell
part of coupling the action potential to contraction
A
part of coupling the action potential to contraction
13
Q
What is the function of the mitochondria?
storage of calcium
houses the genetic material of the cell
making of ATP - the “power house” of the cell
part of coupling the action potential to contraction
A
making of ATP - the “power house” of the cell
14
Q
Which arrangement of the sarcomere gives rise to the H band?
is the point of connection for adjacent thick filaments
the boundary between adjacent sarcomeres
the region of the sarcomere that contains only thin filaments
the region of the resting sarcomere that only contains thick filaments
A
the region of the resting sarcomere that only contains thick filaments
15
Q
Which arrangement of the sarcomere gives rise to the Z line?
is the point of connection for adjacent thick filaments
the region of the sarcomere that contains only thin filaments
the boundary between adjacent sarcomeres
the region of the resting sarcomere that only contains thick filaments
A
the boundary between adjacent sarcomeres
16
Q
The action potential in skeletal muscle fibers is generated by the \_\_\_\_\_\_\_\_\_\_. sarcoplasm sarcoplasmic reticulum sarcophagus sarcolemma
A
sarcolemma
17
Q
Titin is a(n) \_\_\_\_\_\_\_\_\_\_. thin filament protein tropomyosin-binding protein elastic protein calcium-binding protein
A
elastic protein
18
Q
Interactions between actin and myosin filaments of the sarcomere are responsible for
muscle contraction.
muscle fatigue.
the striped appearance of skeletal muscle.
muscle relaxation.
the conduction of neural stimulation to the muscle fiber.
A
muscle contraction.
19
Q
Skeletal muscle fibers are formed from embryonic cells called fascicles. sarcomeres. myofibrils. myomeres. myoblasts.
A
myoblasts.
20
Q
The repeating unit of a skeletal muscle fiber is the sarcolemma. myofibril. myofilament. sarcomere. sarcoplasmic reticulum.
A
sarcomere.
21
Q
The plasma membrane of a skeletal muscle fiber is called the sarcoplasm. sarcolemma. sarcosome. sarcomere. sarcoplasmic reticulum.
A
sarcolemma.
22
Q
Which of the following best describes the term sarcomere?
thin filaments are anchored here
protein that accounts for elasticity of resting muscle
repeating unit of striated myofibrils
largely made of myosin molecules
storage site for calcium ions
A
repeating unit of striated myofibrils
23
Q
Muscle fibers differ from "typical cells" in that muscle fibers are very small. have many nuclei. have large gaps in the cell membrane. lack a plasma membrane. lack mitochondria.
A
have many nuclei.
24
Q
Which of the following best describes the term sarcoplasmic reticulum?
thin filaments are anchored here
repeating unit of striated myofibrils
largely made of myosin molecules
storage and release site for calcium ions
protein that accounts for elasticity of resting muscle
A
storage and release site for calcium ions
25
The skeletal muscle complex known as the triad consists of
A bands, H bands, and I bands.
actin, myosin, and sarcomeres.
actin, myosin, and filaments.
filaments, myofibrils, and sarcomeres.
a transverse tubule and two terminal cisternae.
a transverse tubule and two terminal cisternae.
26
```
The region of the sarcomere that always contains thin filaments is the
Z line.
H band.
A band.
M line.
I band.
```
I band.
27
Which statement about the microscopic anatomy of skeletal muscle fibers is true?
a. Muscle fibers are continuous from tendon to tendon.
b. Cross striations result from the lateral alignment of thick and thin filaments.
c. Each fiber has many nuclei.
d. Tubular extensions of the sarcolemma penetrate the fiber transversely.
e. All of the answers are correct.
e. All of the answers are correct.
28
```
When a skeletal muscle fiber contracts,
the H bands and I bands get smaller.
the width of the A band remains constant.
the zones of overlap get larger.
the Z lines get closer together.
All of the answers are correct.
```
All of the answers are correct.
29
Where would calcium ions be predominately found?
terminal cisterna
30
```
In a neuromuscular junction, synaptic vesicles in the motor neuron contain which neurotransmitter?
dopamine
norepinephrine
acetylcholine (ACh)
serotonin
```
acetylcholine (ACh)
31
```
When an action potential arrives at the axon terminal of a motor neuron, which ion channels open?
voltage-gated calcium channels
voltage-gated potassium channels
chemically gated calcium channels
voltage-gated sodium channels
```
voltage-gated calcium channels
32
What means of membrane transport is used to release the neurotransmitter into the synaptic cleft?
a channel
exocytosis
a protein carrier
exocytosis
33
The binding of the neurotransmitter to receptors on the motor end plate causes which of the following to occur?
a. Binding of the neurotransmitter causes chemically gated sodium channels to open in the motor end plate.
b. Binding causes voltage-gated sodium channels to open in the motor endplate.
c. Binding causes potassium voltage-gated channels to open in the motor endplate.
d. Binding causes chemically gated potassium channels to open in the motor end plate.
a. Binding of the neurotransmitter causes chemically gated sodium channels to open in the motor end plate.
34
How is acetylcholine (ACh) removed from the synaptic cleft?
acetylcholinesterase (AChE; an enzyme)
diffusion away from the synaptic cleft
a reuptake pump on the axon terminal
acetylcholinesterase (AChE; an enzyme)
35
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
sarcolemma
cytosol
terminal cisternae of the sarcoplasmic reticulum
terminal cisternae of the sarcoplasmic reticulum
36
```
Which component of a thin filament binds to calcium once the calcium ion is released from the sarcoplasmic reticulum?
troponin
actin
myosin
tropomyosin
```
troponin
37
```
During neuromuscular transmission, the axon terminals release __________.
sodium ions
acetylcholinesterase
acetylcholine
calcium ions
```
acetylcholine
38
```
The muscle action potential penetrates into a fiber along the __________.
sarcoplasmic reticulum
Z discs
transverse tubules
neuromuscular junction
```
transverse tubules
39
Cycling of myosin cross-bridges results in ___________.
muscle shortening
ATP hydrolysis
force production
Repeated cycling of cross-bridges causes all of these effects.
Repeated cycling of cross-bridges causes all of these effects.
40
```
In response to an action potential along the transverse tubules, the __________ release(s) calcium ions into the sarcoplasm.
thin filaments
sarcoplasmic reticulum
troponin molecules
calcitonin
```
sarcoplasmic reticulum
41
```
In response to action potentials arriving along the transverse tubules, the sarcoplasmic reticulum releases
potassium ions.
hydrogen ions.
sodium ions.
acetylcholine.
calcium ions.
```
calcium ions.
42
```
Each skeletal muscle fiber is controlled by a motor neuron at a single
synaptic cleft.
neuromuscular junction.
synaptic knob.
sarcomere.
transverse tubule.
```
neuromuscular junction.
43
```
The narrow space between the synaptic terminal and the muscle fiber is the
motor unit.
motor end plate.
synaptic knob.
synaptic cleft.
M line.
```
synaptic cleft.
44
```
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
oxygen debt.
rigor mortis.
tetany.
depolarization.
treppe.
```
rigor mortis.
45
```
In rigor mortis
muscles are inextensible.
the myosin heads are attached to actin.
cross-bridge cycling is absent.
ATP is depleted.
All of the answers are correct.
```
All of the answers are correct.
46
Which of the following acts as an ATPase during the contraction cycle of muscle?
tropomyosin molecules
the tail portion of the myosin molecule
troponin molecules
actin molecules
the head portion of the myosin molecule
the head portion of the myosin molecule
47
When calcium ion binds to troponin,
myosin shortens.
tropomyosin moves into the groove between the helical actin strands.
muscle relaxation occurs.
active sites on the myosin are exposed.
actin heads will bind to myosin.
tropomyosin moves into the groove between the helical actin strands.
48
```
The cytoplasm of the neuromuscular terminal contains vesicles filled with molecules of the neurotransmitter
acetylcholine.
adrenaline.
epinephrine.
norepinephrine.
antidiuretic hormone.
```
acetylcholine.
49
```
When contraction occurs,
the I bands get smaller.
the width of the A band remains constant.
the H bands get smaller.
the Z lines move closer together.
All of the answers are correct.
```
All of the answers are correct.
50
The muscle weakness of myasthenia gravis results from
a. excessive acetylcholinesterase that destroys the neurotransmitter.
b. the motor neuron action potential being too small to shock the muscle fibers.
c. insufficient acetylcholine release from presynaptic vesicles.
d. loss of acetylcholine receptors in the end-plate membrane.
e. inability of the muscle fiber to produce ATP.
d. loss of acetylcholine receptors in the end-plate membrane.
51
```
Synaptic vesicles contain neurotransmitters that are released by ________ when the action potential arrives.
apoptosis
sodium
hydrolysis
endocytosis
exocytosis
```
exocytosis
52
A patient takes a medication that blocks ACh receptors of skeletal muscle fibers. What is this drug's effect on skeletal muscle contraction?
a. causes a strong contraction similar to a "charlie horse" cramp
b. increases the muscle's excitability
c. produces a strong, continuous state of contraction
d. reduces the muscle's ability for contraction
e. increases tone in the muscle
d. reduces the muscle's ability for contraction
53
```
What causes the release of calcium from the terminal cisternae of the sarcoplasmic reticulum within a muscle cell?
calcium ion pump
arrival of an action potential
ATP
troponin
```
arrival of an action potential
54
The binding of calcium to which molecule causes the myosin binding sites to be exposed?
tropomyosin
troponin
actin
troponin
55
A myosin head binds to which molecule to form a cross bridge?
A myosin head binds to which molecule to form a cross bridge?
troponin
tropomyosin
actin
actin
56
```
What causes the myosin head to disconnect from actin?
binding of calcium
binding of ATP
binding of troponin
hydrolysis of ATP
```
binding of ATP
57
What energizes the power stroke?
calcium
hydrolysis of ATP
binding of ATP
hydrolysis of ATP
58
```
A single muscle action potential will normally be followed by __________.
a single pulse of calcium ion release
treppe
incomplete tetanus
two pulses of calcium ion release
```
a single pulse of calcium ion release
59
```
A muscle producing its maximum tension is in __________.
complete tetanus
rigor mortis
incomplete tetanus
treppe
```
complete tetanus
60
To increase muscle tension, the nervous system can __________.
increase the stimulation frequency
recruit larger motor units
increase the number of active motor units
All of these can increase muscle tension.
All of these can increase muscle tension.
61
```
In which of the following would the motor units have the fewest muscle fibers?
thigh muscles
calf muscles
muscles that control the eyes
postural muscles of the back
muscles of the neck
```
muscles that control the eyes
62
```
The type of contraction in which the muscle fibers do not shorten is called
isometric.
concentric.
treppe.
isotonic.
tetany.
```
isometric.
63
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.
many twitches always fuse into one.
the peak tension is less than the load.
muscle tension exceeds the load and the muscle lifts the load.
64
What is the type of chemical reaction used to rebuild ADP into ATP?
rehydration synthesis
dehydration synthesis
hydrolysis
dehydration synthesis
65
Which of the following processes produces molecules of ATP and has two pyruvic acid molecules as end products?
glycolysis
Krebs cycle and oxidative phosphorylation
hydrolysis of creatine phosphate
glycolysis
66
Which of the following processes produces 36 ATP?
hydrolysis of creatine phosphate
glycolysis
Krebs cycle and oxidative phosphorylation
Krebs cycle and oxidative phosphorylation
67
The "rest and recovery" period, where the muscle restores depleted reserves, includes all of the following processes EXCEPT __________.
Oxygen rebinds to myoglobin.
Pyruvic acid is converted back to lactic acid.
ATP is used to rephosphorylate creatine into creatine phosphate.
Glycogen is synthesized from glucose molecules.
Pyruvic acid is converted back to lactic acid.
68
Which type of muscle fiber has a large quantity of glycogen and mainly uses glycolysis to synthesize ATP?
red slow twitch fibers
white fast twitch fibers
white fast twitch fibers
69
```
Muscle fatigue occurs due to a buildup of __________ and __________ in pH.
creatine phosphate; decrease
creatine phosphate; increase
lactic acid; decrease
lactic acid; increase
```
lactic acid; decrease
70
During the Cori cycle, in the liver
lactic acid is produced from pyruvic acid.
glucose is produced from lactic acid.
lactic acid is shuffled to muscle cells.
glucose is released from glycogen.
lactic acid is produced from glucose.
glucose is produced from lactic acid.
71
During the recovery period the body's need for oxygen is increased because
the muscles are not producing ATP.
additional oxygen is required to restore energy reserves consumed during exercise.
the liver requires more oxygen to produce lactic acid.
the individual is panting.
muscle cells are producing energy anaerobically.
additional oxygen is required to restore energy reserves consumed during exercise.
72
```
A resting muscle generates most of its ATP by
hydrolysis of creatine phosphate.
the tricarboxylic acid cycle.
aerobic metabolism of fatty acids.
anaerobic respiration.
glycogenolysis.
```
aerobic metabolism of fatty acids.
73
Creatine phosphate
cannot transfer its phosphate group to ADP.
acts as an energy reserve in muscle tissue.
can replace ATP in binding to myosin molecules during contraction.
is produced by the process of anaerobic respiration.
is only formed during strenuous exercise.
acts as an energy reserve in muscle tissue.
74
```
During anaerobic glycolysis
pyruvic acid is produced.
ATP is produced.
carbohydrate is metabolized.
oxygen is not consumed.
All of the answers are correct.
```
All of the answers are correct.
75
```
Aerobic metabolism normally provides ________ percent of the ATP demands of a resting muscle cell.
70
100
50
25
95
```
95
76
```
The __________ type of muscle fiber has relatively few mitochondria.
intermediate
slow
fast
cardiac
```
fast
77
```
Which of these is not a property of slow muscle fibers?
They are rich in myoglobin.
They resist fatigue.
They contract slowly.
They are large in diameter.
```
They are large in diameter.
78
```
The type of muscle fiber that is most resistant to fatigue is the ________ fiber.
anaerobic
fast
high-density
intermediate
slow
```
slow
79
During activities requiring aerobic endurance
glycogen and glycolysis are the primary sources of reserve energy.
fatigue occurs in a few minutes.
most of the muscle's energy is produced in mitochondria.
oxygen debts are common.
oxygen is not required.
most of the muscle's energy is produced in mitochondria.
80
Which of the following statements is (are) true regarding human muscles?
Slow fibers are abundant in the back muscles.
Most have both slow and fast fibers.
Eye muscles are composed entirely of fast fibers.
Slow fibers are abundant in the calf muscles.
All of the answers are correct.
All of the answers are correct.
81
When comparing slow muscle fibers to fast muscle fibers, slow fibers
take about three times as long to reach peak tension.
have much smaller fiber diameters.
generate much less tension.
are rich in the red protein myoglobin.
All of the answers are correct.
All of the answers are correct.
82
```
Large-diameter, densely packed myofibrils, large glycogen reserves, and few mitochondria are characteristics of
fast fibers.
slow fibers.
intermediate fibers.
fatty muscles.
red muscles.
```
fast fibers.
83
Which of these is true of cardiac muscle fibers?
Cardiac fibers branch.
Cardiac fibers have a single nucleus.
Cardiac fibers have a long twitch duration compared to skeletal fibers.
All of these are true of cardiac fibers.
All of these are true of cardiac fibers.
84
```
All of the following are found in both skeletal and cardiac muscle fibers except __________.
mitochondria
striations
intercalated disks
sarcomeres
```
intercalated disks
85
Which of the following statements is false?
Cardiac muscle stimulation is neural.
Skeletal muscle stimulation is neural.
Cardiac muscle contractions cannot be summated.
Skeletal muscle contractions may be summated.
Cardiocytes are interconnected through intercalated discs.
Cardiac muscle stimulation is neural.
86
```
Resting smooth muscle can be stretched without developing much tension because of its __________.
elasticity
extensibility
contractility
plasticity
```
plasticity
87
Which arrangement of the sarcomere gives rise to the M line?
the boundary between adjacent sarcomeres
the region of the sarcomere that contains only thin filaments
the region of the resting sarcomere that only contains thick filaments
is the point of connection for adjacent thick filaments
is the point of connection for adjacent thick filaments
88
Which arrangement of the sarcomere gives rise to the I band?
the boundary between adjacent sarcomeres
the region of the sarcomere that contains only thin filaments
the region of the resting sarcomere that only contains thick filaments
is the point of connection for adjacent thick filaments
the region of the sarcomere that contains only thin filaments
89
```
Which thick filament binds to actin once its active binding sites are exposed?
myosin
tropomyosin
actin
troponin
```
myosin
90
Action potential propagation in a skeletal muscle fiber ceases when acetylcholine is removed from the synaptic cleft. Which of the following mechanisms ensures a rapid and efficient removal of acetylcholine?
a. Acetylcholine is degraded by acetylcholinesterase.
b. Acetylcholine is transported back into the axon terminal by a reuptake mechanism.
c. Acetylcholine is transported into the postsynaptic neuron by receptor-mediated endocytosis.
d. Acetylcholine diffuses away from the cleft.
a. Acetylcholine is degraded by acetylcholinesterase.
91
The neuromuscular junction is a well-studied example of a chemical synapse. Which of the following statements describes a critical event that occurs at the neuromuscular junction?
a. Acetylcholine is released by axon terminals of the motor neuron.
b. Acetylcholine binds to its receptor in the junctional folds of the sarcolemma. Its receptor is linked to a G protein.
c. Acetylcholine is released and moves across the synaptic cleft bound to a transport protein.
d. When the action potential reaches the end of the axon terminal, voltage-gated sodium channels open and sodium ions diffuse into the terminal.
a. Acetylcholine is released by axon terminals of the motor neuron.
92
Action potentials travel the length of the axons of motor neurons to the axon terminals. These motor neurons __________.
a. extend from the brain to the sarcolemma of a skeletal muscle fiber
b. arise in the epimysium of a skeletal muscle and extend to individual skeletal muscle fibers
c. extend from the brain or spinal cord to the sarcolemma of a skeletal muscle fiber
d. extend from the spinal cord to the sarcolemma of a skeletal muscle fiber
c. extend from the brain or spinal cord to the sarcolemma of a skeletal muscle fiber
93
Calcium entry into the axon terminal triggers which of the following events?
a. Synaptic vesicles fuse to the plasma membrane of the axon terminal and release acetylcholine.
b. Acetylcholine is released into the cleft by active transporters in the plasma membrane of the axon terminal.
c. Acetylcholine binds to its receptor.
d. Cation channels open and sodium ions enter the axon terminal while potassium ions exit the axon terminal.
a. Synaptic vesicles fuse to the plasma membrane of the axon terminal and release acetylcholine.
94
Acetylcholine binds to its receptor in the sarcolemma and triggers __________.
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 anion channels
the opening of ligand-gated cation channels
95
Sodium and potassium ions do not diffuse in equal numbers through ligand-gated cation channels. Why?
a. The inside surface of the sarcolemma is negatively charged compared to the outside surface. Sodium ions diffuse inward along favorable chemical and electrical gradients.
b. The outside surface of the sarcolemma is negatively charged compared to the inside surface. Potassium ions diffuse outward along favorable chemical and electrical gradients.
c. The outside surface of the sarcolemma is negatively charged compared to the inside surface. Sodium ions diffuse outward along favorable chemical and electrical gradients.
d. The inside surface of the sarcolemma is negatively charged compared to the outside surface. Potassium ions diffuse inward along favorable chemical and electrical gradients.
a. The inside surface of the sarcolemma is negatively charged compared to the outside surface. Sodium ions diffuse inward along favorable chemical and electrical gradients.
96
Excitation-contraction coupling is a series of events that occur after the events of the neuromuscular junction have transpired. The term excitation refers to which step in the process?
a. Excitation refers to the release of calcium ions from the sarcoplasmic reticulum.
b. Excitation, in this case, refers to the propagation of action potentials along the sarcolemma.
c. Excitation refers to the shape change that occurs in voltage-sensitive proteins in the sarcolemma.
d. Excitation refers to the propagation of action potentials along the axon of a motor neuron.
b. Excitation, in this case, refers to the propagation of action potentials along the sarcolemma.
97
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.
Sodium release from the sarcoplasmic reticulum initiates the contraction.
Action potentials propagate into the interior of the skeletal muscle fiber.
Calcium release from the sarcoplasmic reticulum initiates the contraction.
Calcium release from the sarcoplasmic reticulum initiates the contraction.
98
A triad is composed of a T-tubule and two adjacent terminal cisternae of the sarcoplasmic reticulum. How are these components connected?
Potassium leak channels.
A series of proteins that control calcium release.
Voltage-gated sodium channels.
Myosin cross-bridge binding sites.
A series of proteins that control calcium release.
99
```
What is the name given to the regularly spaced infoldings of the sarcolemma?
terminal cisternae
transverse or T tubules
sarcoplasmic reticulum
motor endplates
```
transverse or T tubules
100
```
Which of the following is most directly responsible for the coupling of excitation to contraction of skeletal muscle fibers?
Acetylcholine.
Calcium ions.
Sodium ions.
Action potentials.
```
Calcium ions.
101
What is the relationship between the number of motor neurons recruited and the number of skeletal muscle fibers innervated?
a. A skeletal muscle fiber is innervated by multiple motor neurons.
b. A motor neuron typically innervates only one skeletal muscle fiber.
c. Typically, hundreds of skeletal muscle fibers are innervated by a single motor neuron.
d. Motor neurons always innervate thousands of skeletal muscle fibers.
c. Typically, hundreds of skeletal muscle fibers are innervated by a single motor neuron.
102
```
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
Calcium bound to troponin
Troponin bound to tropomyosin
A myosin head bound to actin
```
A myosin head bound to actin
103
```
What structure is the functional unit of contraction in a skeletal muscle fiber?
The junctional folds of the sarcolemma
The sarcomere
The cross bridge
The triad
```
The sarcomere
104
```
Calcium ions couple excitation of a skeletal muscle fiber to contraction of the fiber. Where are calcium ions stored within the fiber?
in the transverse tubules.
in the sarcoplasmic reticulum.
in the nuclei.
in the mitochondria.
```
in the sarcoplasmic reticulum.
105
After a power stroke, the myosin head must detach from actin before another power stroke can occur. What causes cross bridge detachment?
ADP and inorganic phosphate are bound to the myosin head.
Calcium ions bind to troponin.
Acetylcholine binds to receptors in the junctional folds of the sarcolemma.
ATP binds to the myosin head.
ATP binds to the myosin head.
106
How does the myosin head obtain the energy required for activation?
1. The energy comes from the hydrolysis of ATP.
2. The energy comes from the direct phosphorylation of ADP by creatine phosphate.
3. The energy comes from the hydrolysis of GTP.
4. The energy comes from oxidative phophorylation.
1. The energy comes from the hydrolysis of ATP.
107
What specific event triggers the uncovering of the myosin binding site on actin?
1. Calcium ions bind to tropomyosin and change its shape.
2. Calcium release channels open in the sarcoplasmic reticulum, and calcium levels rise in the sarcoplasm.
3. Sodium ions bind to troponin and change its shape.
4. Calcium ions bind to troponin and change its shape.
4. Calcium ions bind to troponin and change its shape.
108
When does cross bridge cycling end?
1. Cross bridge cycling ends when ATP binds to the myosin head.
2. Cross bridge cycling ends when sufficient calcium has been actively transported back into the sarcoplasmic reticulum to allow calcium to unbind from troponin.
3. Cross bridge cycling ends when calcium release channels in the sarcoplasmic reticulum open.
4. Cross bridge cycling ends when calcium ions are passively transported back into the sarcoplasmic reticulum.
2. Cross bridge cycling ends when sufficient calcium has been actively transported back into the sarcoplasmic reticulum to allow calcium to unbind from troponin.
109
```
The neuromuscular junction is a connection between a neuron and a __________.
muscle fiber
synaptic terminal
vesicle
myofibril
```
muscle fiber
110
```
The end of a neuron, where acetylcholine-filled vesicles are located, is called the __________.
synaptic cleft
motor end plate
acetylcholine receptor
synaptic terminal
```
synaptic terminal
111
What is the synaptic cleft?
the region of the neuron containing synaptic vesicles
the border between the motor end plate and the sarcolemma
the space between the synaptic terminal and the motor end plate
the step where acetylcholinesterase (AChE) breaks down, or cleaves, acetylcholine
the space between the synaptic terminal and the motor end plate
112
```
Inside a neuron, acetylcholine is contained within __________.
acetylcholine receptors
the motor end plate
the synaptic cleft
vesicles
```
vesicles
113
What causes the vesicles inside a neuron to fuse with the plasma membrane?
acetylcholine being broken down by acetylcholinesterase
an action potential in the neuron
an action potential in the muscle fiber
acetylcholine binding to acetylcholine receptors
an action potential in the neuron
114
```
Acetylcholine receptors are primarily located __________.
inside vesicles
on the synaptic terminal
inside the muscle fiber
on the motor end plate
```
on the motor end plate
115
An action potential in the muscle fiber causes __________.
the release of acetylcholine into the synaptic cleft
acetylcholinesterase to break down acetylcholine
the muscle fiber to contract
acetylcholine to bind to receptors on the motor end plate
the muscle fiber to contract
116
The role of acetylcholinesterase in the neuromuscular junction is to __________.
generate a muscle action potential
remove acetylcholine from the synaptic cleft
increase the sodium permeability of the motor end plate
release acetylcholine from the synaptic terminal
remove acetylcholine from the synaptic cleft
117
```
Inside a muscle, bundles of single muscle fibers form __________.
T tubules
sarcomeres
fascicles
thick filaments
```
fascicles
118
```
The muscle action potentials that initiate contraction are transmitted from the sarcolemma into the interior of the muscle fiber by __________.
the sarcoplasmic reticulum
T tubules
myofibrils
myofilaments
```
T tubules
119
```
T tubules and the terminal cisternae are clustered into structures called __________.
fascicles
myofibrils
sarcomeres
triads
```
triads
120
```
The sarcoplasmic reticulum contains __________.
calcium
myofilaments
troponin
T tubules
```
calcium
121
```
Which organelle completely surrounds each myofibril inside a muscle fiber?
fascicle
calcium
nucleus
sarcoplasmic reticulum
```
sarcoplasmic reticulum
122
```
To what regulatory protein does calcium bind during the initiation of the contraction cycle in skeletal muscle fibers?
troponin
myosin
tropomyosin
actin
```
troponin
123
Which of the following causes the active site on actin to be exposed or uncovered?
calcium entering the sarcoplasmic reticulum
tropomyosin shifting position
troponin releasing calcium
cross-bridge formation
tropomyosin shifting position
124
Which of the following most correctly describes excitation in the context of excitation-contraction coupling in skeletal muscle?
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
125
Which of the following phrases best describes how excitation is coupled to contraction in skeletal muscle fibers?
through calcium release from the sarcoplasmic reticulum
through T tubules
through electrical impulses travelling along the sarcolemma
through cross-bridge formation
through calcium release from the sarcoplasmic reticulum
126
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?
1. The muscles would contract because of calcium binding to troponin.
2. The muscles would contract because of increased nerve stimulation.
3. The muscles would relax because of calcium being pumped back into the sarcoplasmic reticulum.
4. The muscles would contract because of increased action potential generation in the sarcolemma.
1. The muscles would contract because of calcium binding to troponin.
127
Myofibrils are __________.
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
128
```
Z lines define the edges of which of the following?
sarcomeres
myofibrils
cross-bridges
myosin
```
sarcomeres
129
```
Myosin molecules form what part of the sarcomere?
thin filament
actin
thick filament
tropomyosin
```
thick filament
130
```
Which of the following is involved in the power stroke?
tropomyosin
myosin
myofibrils
Z lines
```
myosin
131
```
Which of the following proteins contains the active site involved in cross-bridge formation?
tropomyosin
actin
myosin
troponin
```
actin
132
```
When the sarcomere is at rest, what is covering the active sites on actin?
tropomyosin
cross-bridges
troponin
myosin
```
tropomyosin
133
```
When calcium is released inside a muscle cell, what does it bind to?
actin
troponin
tropomyosin
myosin
```
troponin
134
```
Myosin molecules form cross-bridges when they attach to __________.
troponin
calcium
actin
tropomyosin
```
actin
135
What happens immediately after the myosin head binds to the active site on actin?
ATP binds to the myosin head.
Tropomyosin moves away from the active site on actin.
The myosin head detaches from the active site on actin.
The myosin head pivots, moving the actin strand.
The myosin head pivots, moving the actin strand.
136
```
ATP binding leads to which of the following actions?
cross-bridge formation
pivoting of the myosin head
exposure of active sites on actin
detaching and resetting cross-bridges
```
detaching and resetting cross-bridges
