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Human Physiology - Problem Drill 12: Muscle Physiology
Question No. 1 of 10
Instruction: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
1. Which of these muscles appear striated?
Question #01
(A) Skeletal
(B) Smooth
(C) Cardiac
(D) A & C
(E) All of the above
A. Incorrect!
Skeletal muscle is striated because of its banding but it is not the only striated
muscle.
B. Incorrect!
Smooth muscle is not striated muscle because of its lack of banding.
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Choice
C. Incorrect!
Cardiac muscle is striated because of its banding but it is not the only striated
muscle.
D. Correct!
Both the skeletal and cardiac muscle has alternating band of thin and thick
filaments that give the muscle the appearance of striations.
E. Incorrect!
Not all of these muscles have the banding that makes them appear striated.
Solution
Skeletal muscles are arranged in long fibers and they are large multinucleated cells
that appear striated. Smooth muscles are smaller cells that are uninucleated. They
are arranged as spindle shaped cells and do not appear striated. Cardiac muscle are
striated, uninucleated cells that appear branched.
The correct answer is (D).
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Question No. 2 of 10
Instruction: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
2. Which of the following is used for voluntary movement?
Question #02
(A) Skeletal
(B) Smooth
(C) Cardiac
(D) A & C
(E) All of the above
A. Correct!
Skeletal muscles are attached to bones of the skeleton and responsible for
voluntary movement of the body. They are the only muscles that are under
conscious control.
B. Incorrect!
Smooth muscles are the chief muscles found in internal organs and tubes. Smooth
muscles are responsible for movement of materials into, out of and within the body.
This movement is not under conscious control.
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Choice
C. Incorrect!
Cardiac muscle is found only in the heart and is responsible for contraction of the
heart. This movement is not under conscious control.
D. Incorrect!
Only skeletal muscle is under conscious control and not both skeletal and cardiac.
E. Incorrect!
Not all of these muscles are important for voluntary control and conscious
movement of the body.
Skeletal muscles are attached to bones of the skeleton and responsible for
voluntary movement of the body. Smooth muscles are the chief muscles found in
internal organs and tubes like the stomach, bladder and blood vessels. Smooth
muscles are responsible for movement of materials into, out of and within the body.
Cardiac muscle is found only in the heart and is responsible for contraction of the
heart.
The correct answer is (A).
Solution
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Question No. 3 of 10
Instruction: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
3. Which of the following is/are contractile protein(s) found in the sarcomeres of
skeletal muscle?
Question #03
(A) Troponin
(B) Actin
(C) Tropomyosin
(D) Titin
(E) A & C
A. Incorrect!
Troponin is the regulatory protein that is found in the thin filaments of skeletal
muscle.
B. Correct!
Actin is the contractile protein that is found in the thin filaments of skeletal muscle.
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Choice
C. Incorrect!
Tropomyosin is the regulatory protein that is found in the thin filaments of skeletal
muscle.
D. Incorrect!
Titin is the accessory protein that is found in skeletal muscle.
E. Incorrect!
Both troponin and tropomyosin are the regulatory proteins that are found in the
thin filaments of skeletal muscle.
Solution
The myofibril is composed of sarcomeres. Each sarcomere is composed of several
types of proteins. There are the accessory proteins called titin and nebulin which
aid in contraction. Titin is a huge molecule that stabilizes the position of the
contractile filaments and its elasticity helps to return the stretched muscle to
resting position. Nebulin helps with alignment of the actin filaments in the
sarcomere. There are also contractile proteins called actin and myosin and they are
directly responsible for muscle contraction. The other proteins are the regulatory
proteins called tropomyosin and troponin which also aid in contraction. The myosin
makes up the thick filament and the tropomyosin, troponin and the actin make up
the thin filaments.
The correct answer is (B).
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Question No. 4 of 10
Instruction: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
4. What is a single contraction-relaxation cycle?
Question #04
(A) Tension
(B) Summation
(C) Twitch
(D) Tetanus
(E) Isometric contractions
A. Incorrect!
Tension is the rising slope of the twitch curve. Tension is a component of the
twitch.
B. Incorrect!
Summation occurs when there is no rest between action potentials. So the fiber
does not have time to rest between stimuli and there is a more forceful contraction.
The twitch occurs as part of summation.
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Choice
C. Correct!
The twitch is a single contraction-relaxation cycle.
D. Incorrect!
Tetanus is the state of maximal contraction. If the action potential continues to
stimulate the muscle fiber repeatedly at short intervals, relaxation between
contractions diminishes until the fiber achieves tetanus.
E. Incorrect!
Isometric contractions are contractions that create force without movement. The
twitch occurs within the contraction.
A single contraction-relaxation cycle is called a twitch. A single action potential
invokes a twitch. There is a latent period between the action potential and the
beginning of muscle tension. This interval is the time required for mechanisms that
are needed for contraction to occur. Once contraction beings, tension increases
steadily. Tension is the rising slope of the twitch curve.
The correct answer is (C).
Solution
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Question No. 5 of 10
Instruction: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
5. What occurs when the muscle is no longer able to generate or sustain power?
Question #05
(A) Tetanus
(B) Summation
(C) Tension
(D) Cramp
(E) Fatigue
A. Incorrect!
Tetanus is the state of maximal contraction. If the action potential continues to
stimulate the muscle fiber repeatedly at short intervals, relaxation between
contractions diminishes until the fiber achieves tetanus. This has nothing to do with
the inability to generate or sustain power.
B. Incorrect!
Summation occurs when there is no rest between action potentials. So the fiber
does not have time to rest between stimuli and there is a more forceful contraction.
This has nothing to do with the inability to generate or sustain power.
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Choice
C. Incorrect!
The tension is the rising slope of the twitch curve. Tension is a component of the
twitch and has nothing to do with the inability to generate or sustain power.
D. Incorrect!
A muscle cramp is a sustained painful contraction of the skeletal muscle. This has
nothing to do with the inability to generate power.
E. Correct!
Fatigue is a condition in which the muscle is no longer able to generate or sustain
power.
Fatigue is a condition in which the muscle is no longer able to generate or sustain
power. Fatigue is highly variable and is influenced by the intensity and duration of
activity, the type of ATP source whether aerobic or anaerobic, composition of
muscle and fitness level of the individual.
Solution
The correct answer is (E).
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Question No. 6 of 10
Instruction: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
6. Which of the following statements is correct?
Question #06
(A) Fast twitch glycolytic fibers are dark red in color due to the presence of
myoglobin.
(B) Fast twitch glycolytic fibers are used for activities like jumping.
(C) Fast twitch oxidative fibers are used for activities like sprinting.
(D) Fast twitch oxidative fibers fatigue easily.
(E) None of these statements are correct.
A. Incorrect!
The fast twitch glycolytic fibers have the least amount of myoglobin and they
appear white or pale.
B. Correct!
The fast twitch glycolytic fibers are used for generating quick bursts needed for
activities like jumping.
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Choice
C. Incorrect!
The fast twitch oxidative fibers are used for activities like walking not those that
require quick burst of energy.
D. Incorrect!
Fast twitch oxidative fibers can undergo glycolysis and then oxidative
phosphorylation to generate energy so they do not tire easily.
E. Incorrect!
One of these statements is correct so this can not be the right answer.
Solution
There are three types of skeletal muscle fibers. They are slow, twitch oxidative,
fast twitch oxidative and fast twitch glycolytic. The slow twitch has the smallest
diameter of the muscle fibers with the fast twitch glycolytic having the largest. The
longest duration of contraction occurs in the slow twitch oxidative. These fibers are
used for strong and sustained movements. Consequently, they are resistant to
fatigue. The fast twitch glycolytic has short contraction duration and fatigues easily
because of the accumulation of lactic acid due to glycolysis leading to acidosis. The
fast twitch oxidative has short duration but it is more fatigue resistance than the
fast twitch glycolytic. The fast twitch oxidative is used for standing and walking
and the fast twitch glycolytic is used for generating quick bursts needed for
activities like jumping. Slow twitch uses oxidative phosphorylation and the fast
twitch oxidative used glycolysis but becomes oxidative during sustained activities.
The fast twitch glycolytic uses glycolysis solely. The slow twitch fibers are called red
muscle because they contain large amounts of myoglobin which is the red oxygenbinding pigment. The slow twitch are dark red in color because they have the most
myoglobin and the fast twitch glycolytic have the least and appear white or pale.
Tension development is fastest in the fast twitch glycolytic and slowest in the slow
twitch oxidative fibers.
The correct answer is (B).
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Question No. 7 of 10
Instruction: (1) Read the problem statement and answer choices carefully (2) Work the problems
on paper as needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
7. Which of the following statements is incorrect?
Question #07
(A) Slow twitch oxidative fibers have a large diameter and are fatigue resistant.
(B) Slow twitch oxidative fibers are the most used and are dark red in color
because of the large amount of myoglobin.
(C) Fast twitch glycolytic fibers have a large diameter and short contraction
duration.
(D) Fast twitch oxidative fibers use glycolysis and then oxidative phosphorylation
for ATP generation.
(E) All of the above are correct.
A. Incorrect!
Slow twitch oxidative fibers do have a large diameter and are fatigue resistant. This
statement is correct.
B. Incorrect!
Slow twitch oxidative fibers are the most used and are dark red in color because of
the large amount of myoglobin. This statement is correct.
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Choice
C. Incorrect!
Fast twitch glycolytic fibers have a large diameter and short contraction duration.
This statement is correct.
D. Incorrect!
Fast twitch oxidative fibers use glycolysis and then oxidative phosphorylation for
ATP generation. This statement is correct.
E. Correct!
All of these statements are correct concerning the muscle fibers.
Solution
There are three types of skeletal muscle fibers. They are slow, twitch oxidative,
fast twitch oxidative and fast twitch glycolytic. The slow twitch has the smallest
diameter of the muscle fibers with the fast twitch glycolytic having the largest. The
longest duration of contraction occurs in the slow twitch oxidative. These fibers are
used for strong and sustained movements. Consequently, they are resistant to
fatigue. The fast twitch glycolytic has short contraction duration and fatigues easily
because of the accumulation of lactic acid due to glycolysis leading to acidosis. The
fast twitch oxidative has short duration but it is more fatigue resistance than the
fast twitch glycolytic. The fast twitch oxidative is used for standing and walking
and the fast twitch glycolytic is used for generating quick bursts needed for
activities like jumping. Slow twitch uses oxidative phosphorylation and the fast
twitch oxidative used glycolysis but becomes oxidative during sustained activities.
The fast twitch glycolytic uses glycolysis solely. The slow twitch fibers are called red
muscle because they contain large amounts of myoglobin which is the red oxygenbinding pigment. The slow twitch are dark red in color because they have the most
myoglobin and the fast twitch glycolytic have the least and appear white or pale.
Tension development is fastest in the fast twitch glycolytic and slowest in the slow
twitch oxidative fibers.
The correct answer is (E).
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Question No. 8 of 10
Instruction: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
8. Which of the following statements is incorrect?
Question #08
(A)
(B)
(C)
(D)
(E)
Isometric contraction is the contraction that creates force and moves a load.
Eccentric contraction is the isotonic lengthening of the muscle.
Concentric contraction is the isotonic shortening of the muscle.
Isotonic contractions are used to move objects.
None of the above statements are incorrect.
A. Correct!
Isometric contractions are not contractions that create force and move a load. This
statement is incorrect.
B. Incorrect!
Eccentric contraction is the isotonic lengthening of the muscle. This statement is
correct.
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Choice
C. Incorrect!
Concentric contraction is the isotonic shortening of the muscle This statement is
correct.
D. Incorrect!
Isotonic contractions are contractions used to move objects. This statement is
correct.
E. Incorrect!
One of the statements listed below is incorrect so this could not be the answer.
Solution
Isotonic contractions are any contraction that creates force and moves a load. A
concentric action is one where the bicep muscles are shortened for example. An
eccentric action is the lengthening of muscle. We use isotonic contractions to move
things. Isometric contractions are contractions that create force without movement.
An example would be picking up a weight and holding it stationary in front of you.
This ability is due to the elastic fibers in the tendons and other connective tissues
that attach to the muscle. When sarcomeres shorten in an isometric contraction,
the elastic fibers stretch and this allow the muscle to maintain at a constant length
even though the sarcomeres are shortening creating tension.
The correct answer is (A).
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Question No. 9 of 10
Instruction: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
9. Which of the following statements is correct?
Question #09
(A) Smooth muscle lacks T-tubules and has reduced or absent SR.
(B) Cardiac muscle lack T-tubules but have SR.
(C) Skeletal muscle has the slowest contraction speed.
(D) All muscle types have gap junctions.
(E) All of the above are incorrect.
A. Correct!
Smooth muscle lacks T-tubules and has reduced or absent SR. This statement is
correct.
B. Incorrect!
Cardiac muscle contains T-tubules and has SR. This statement is incorrect.
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Choice
C. Incorrect!
Skeletal muscle actually has the fastest contraction speed. This statement is
incorrect.
D. Incorrect!
Not all muscle types have gap junctions because skeletal muscles lack gap
junctions. This statement is incorrect.
E. Incorrect!
Of the choices available there is one of them that is actually correct.
Solution
Both skeletal and cardiac muscles appear striated due to the present of the banding
of their sarcomeres. Both smooth and cardiac muscle are under involuntary control
while skeletal muscles are for voluntary movement. Morphologically, the skeletal
muscle has large fibers with multiple nuclei, the smooth muscles have smalls
spindle cells with single nuclei and cardiac muscle have short branched cells with
single nuclei. The skeletal muscles lack gap junctions between the fibers and they
have the fastest contraction speed. Smooth muscles have the slowest contraction
speed with cardiac muscle being intermediate. Both smooth and cardiac muscle
have gap junction. Both skeletal and cardiac muscles have T-tubules and extensive
SR while the smooth muscle lacks T-tubules and has reduced or absent SR.
The correct answer is (A).
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Question No. 10 of 10
Instruction: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
10. Which of the following statements in incorrect.
Question #10
(A) Smooth muscle is made of spindle shaped cells that are uninucleated.
(B) Smooth muscle is used for sustained contractions.
(C) Smooth muscle does not have a sarcomere arrangement.
(D) Smooth muscle contains more actin.
(E) All of these statements are correct.
A. Incorrect!
Smooth muscle is made of spindle shaped cells that are uninucleated. This
statement is correct.
B. Incorrect!
Smooth muscle is used for sustained contractions. This statement is correct.
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Choice
C. Incorrect!
Smooth muscle does not have a sarcomere arrangement. This statement is correct.
D. Incorrect!
Smooth muscle does have more actin than skeletal muscles.
E. Correct!
All of the statements above are correct so this is the only correct choice available.
Solution
Smooth muscle is made of spindle shaped cells. The contractile proteins are not
arranged in sarcomeres so it does not appear striated. The actin and myosin are
arranged in long bundles that form a lattice around the central nucleus. There is
more actin in smooth muscle. There are no T-tubules and there is a reduced or
absent sarcoplasmic reticulum. Smooth muscle is designed for sustained
contractions. There are two types of smooth muscle. Most of the smooth muscle is
single unit smooth muscle. This is found in the walls of internal organs and has
numerous of gap junctions. These allow action potentials to transfer rapidly from
cell to cell. The second type is the multi-unit smooth muscle. It is found in the eye
and the reproductive tracts. These cells are not linked electrically. This allows fine
control contractions that are linked directly to neural stimulation.
The correct answer is (E).
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