Essentials of Anatomy and Physiology, 9e (Marieb)
Chapter 6 The Muscular System
Short Answer
Figure 6.1
Using Figure 6.1, match the following:
1) The I band within a skeletal muscle fiber is indicated by letter __________.
Answer: B
Diff: 1
Page Ref: 188
2) The A band within a skeletal muscle fiber is indicated by letter __________.
Answer: A
Diff: 2
Page Ref: 188
3) The lighter central area of the A band is indicated by letter __________.
Answer: D
Diff: 2
Page Ref: 188
4) The thin filament is indicated by letter __________.
Answer: C
Diff: 2
Page Ref: 188
1
Figure 6.2
Using Figure 6.2, match the following:
5) The connective tissue "overcoat" that wraps the entire muscle is indicated by letter
__________.
Answer: A
Diff: 1
Page Ref: 185
6) The connective tissue that wraps a fascicle, or bundle of muscle fibers, is indicated by letter
__________.
Answer: C
Diff: 2
Page Ref: 185
7) The muscle fiber is indicated by letter __________.
Answer: D
Diff: 1
Page Ref: 185
8) The endomysium that wraps individual muscle fibers is indicated by letter __________.
Answer: B
Diff: 1
Page Ref: 185
Fill in the blank or provide a short answer:
9) Only __________ muscle cells are cylindrical and multinucleated.
Answer: skeletal
Diff: 1
Page Ref: 184
10) The muscle tissue that normally exhibits voluntary contractions is __________ muscle.
Answer: skeletal
Diff: 1
Page Ref: 185
11) Only __________ muscle cells possess intercalated discs.
Answer: cardiac
Diff: 1
Page Ref: 186
2
12) Skeletal muscle is often attached to bone by strong, cordlike structures called __________.
Answer: tendons
Diff: 1
Page Ref: 185
13) The __________ zone of a sarcomere contains no actin filaments while the skeletal muscle is
at rest (noncontractile state).
Answer: H
Diff: 1
Page Ref: 187; 189
14) The heads of the myosin myofilaments are called __________ when they link the thick and
thin filaments together during skeletal muscle contraction.
Answer: cross bridges
Diff: 1
Page Ref: 189
15) The gap between the motor neuron and the muscle fiber it supplies at the neuromuscular
junction is called the __________.
Answer: synaptic cleft
Diff: 1
Page Ref: 189
16) When a skeletal muscle is fully contracted, the __________ are closer to the thick filaments.
Answer: Z discs
Diff: 2
Page Ref: 192
17) The only energy source that can be used to directly power muscle activity is __________.
Answer: ATP
Diff: 2
Page Ref: 195
18) A smooth, sustained contraction is called __________.
Answer: tetanus
Diff: 1
Page Ref: 194
19) The __________ of a muscle is attached to the immovable or less movable bone.
Answer: origin
Diff: 1
Page Ref: 198-199
20) The movement that is commonly seen in a ball-in-socket joint, that includes a combination of
flexion, extension, abduction, and adduction, is called __________.
Answer: circumduction
Diff: 2
Page Ref: 199
21) The muscle that has the major responsibility for causing a particular movement is the
__________.
Answer: prime mover
Diff: 1
Page Ref: 202
22) The arrangement of fascicles in orbicularis oris is __________.
Answer: circular
Diff: 1
Page Ref: 204; 207
3
23) The muscle referred to as the "smiling" muscle because it raised the corners of the mouth
upward is the __________.
Answer: zygomaticus
Diff: 2
Page Ref: 207
24) The __________ muscle runs deep to the external oblique muscle.
Answer: internal oblique
Diff: 1
Page Ref: 209
25) The quadriceps femoris muscle group is composed of the three vastus muscles and the
__________ muscle.
Answer: rectus femoris
Diff: 2
Page Ref: 214
26) An inherited disease that causes muscles to degenerate and atrophy is known as __________.
Answer: muscular dystrophy
Diff: 2
Page Ref: 221
Multiple Choice
1) Muscle tissue that has involuntary regulation of contraction is:
A) cardiac muscle only
B) smooth muscle only
C) skeletal muscle only
D) cardiac muscle and smooth muscle
E) cardiac muscle and skeletal muscle
Answer: D
Diff: 2
Page Ref: 185-186
2) The muscle tissue type that consists of single, very long, cylindrical, multinucleate cells with
very obvious striations is:
A) cardiac muscle only
B) smooth muscle only
C) skeletal muscle only
D) cardiac and smooth muscle
E) cardiac and skeletal muscle
Answer: C
Diff: 2
Page Ref: 183-185
4
Figure 6.3
3) The type of muscle tissue pictured in Figure 6.3 is:
A) skeletal muscle
B) voluntary
C) striated
D) found only in the heart
E) smooth muscle
Answer: E
Diff: 2
Page Ref: 184
4) The plasma membrane of a muscle cell is called the:
A) sarcolemma
B) sarcomere
C) myofilament
D) sarcoplasm
E) sarcoplasmic reticulum
Answer: A
Diff: 3
Page Ref: 187
5) Which of the following does not describe cardiac muscle tissue:
A) uninucleate
B) striations
C) involuntary
D) rhythmic contractions
E) attached to bones
Answer: E
Diff: 2
Page Ref: 186
6) What type of membrane wraps a fascicle:
A) endomysium
B) epimysium
C) aponeuroses
D) perimysium
E) tendons
Answer: D
Diff: 2
Page Ref: 185
5
7) Which of the following is NOT a function of the muscular system:
A) production of movement
B) maintenance of posture
C) stabilization of joints
D) generation of heat
E) hematopoiesis
Answer: E
Diff: 1
Page Ref: 187
8) A sarcomere is:
A) the nonfunctional unit of skeletal muscle
B) the contractile unit between two Z discs
C) the area between two intercalated discs
D) the wavy lines on the cell, as seen in a microscope
E) a compartment in a myofilament
Answer: B
Diff: 2
Page Ref: 187
9) Which one of the following is composed of myosin protein:
A) thick filaments
B) thin filaments
C) all myofilaments
D) Z discs
E) light bands
Answer: A
Diff: 2
Page Ref: 187-189
10) Place these structures of the skeletal muscle in order from largest to smallest:
1.
fascicle
2.
myofilament
3.
muscle fiber (cell)
4.
myofibril
5.
sarcomere
A) 1, 3, 4, 5, 2
B) 1, 4, 3, 2, 5
C) 2, 5, 4, 3, 1
D) 3, 1, 2, 4, 5
E) 3, 2, 5, 4, 1
Answer: A
Diff: 3
Page Ref: 185-189
11) The axon terminals of a nerve cell and the sarcolemma of a skeletal muscle cell join at the:
A) motor unit
B) neuromuscular junction
C) synaptic cleft
D) action potential
E) myofibril
Answer: B
Diff: 3
Page Ref: 189
6
12) Which one of the following functions do calcium ions perform during skeletal muscle
contraction:
A) increase the action potential transmitted along the sarcolemma
B) release the inhibition on Z discs
C) expose myosin binding sites on the actin
D) cause ATP binding to actin
E) bind to regulatory proteins on the myosin filaments, changing both their shape and
their position on the thick filaments
Answer: C
Diff: 2
Page Ref: 193
13) The mechanical force of contraction is generated by:
A) shortening of the thick filaments
B) shortening of the thin filaments
C) a sliding of thin filaments past thick ones
D) the "accordian-like" folding of thin and thick filaments
E) the temporary disappearance of thin filaments
Answer: C
Diff: 2
Page Ref: 192
14) Acetylcholine is:
A) an ion pump on the postsynaptic membrane
B) a source of energy for muscle contraction
C) a component of thick myofilaments
D) an oxygen-binding protein
E) a neurotransmitter that stimulates skeletal muscle
Answer: E
Diff: 1
Page Ref: 189
15) The gap between the axon terminal of a motor neuron and the sarcolemma of a skeletal
muscle cell is called the:
A) motor unit
B) sarcomere
C) neuromuscular junction
D) synaptic cleft
E) cross bridge
Answer: D
Diff: 2
Page Ref: 189
16) Neurotransmitters are released upon stimulation from a nerve impulse by the:
A) myofibrils
B) motor unit
C) thick filaments
D) axon terminals of the motor neuron
E) sarcolemma of the muscle cell
Answer: D
Diff: 2
Page Ref: 189
7
17) An elaborate and specialized network of membranes in skeletal muscle cells that function in
calcium storage is the:
A) sarcolemma
B) mitochondria
C) intermediate filament network
D) myofibrillar network
E) sarcoplasmic reticulum
Answer: E
Diff: 1
Page Ref: 189
18) During skeletal muscle contraction, myosin cross bridges attach to active sites of:
A) myosin filaments
B) actin filaments
C) Z discs
D) thick filaments
E) the H zone
Answer: B
Diff: 1
Page Ref: 192
19) The major function of the sarcoplasmic reticulum in skeletal muscle contraction is to:
A) make and store phosphocreatine
B) synthesize actin and myosin myofilaments
C) provide a source of myosin for the contraction process
D) regulate intracellular calcium concentration
E) store ATP
Answer: D
Diff: 2
Page Ref: 189
20) The striations that give skeletal muscle its characteristic striped appearance are produced,
for the most part, by:
A) a difference in the thickness of the sarcolemma
B) the arrangement of myofilaments
C) the sarcoplasmic reticulum
D) the T tubules
E) the "cocked" positions of the heads of the thick filaments
Answer: B
Diff: 2
Page Ref: 189
21) Which of these events must occur first to trigger the skeletal muscle to generate an action
potential and contract:
A) sodium ions rush into the cell
B) acetylcholine (ACh) causes temporary permeability to sodium
C) diffusion of potassium ions out of the cell
D) operation of the sodium-potassium pump
E) acetylcholinesterase (AchE) breaks down acetylcholine (ACh)
Answer: B
Diff: 3
Page Ref: 189-190
8
22) A skeletal muscle twitch differs from a tetanic contraction in that:
A) the tetanic contraction is considered abnormal, while the twitch is a normal muscle
response
B) the tetanic contraction is caused by a single stimulus, while the twitch is caused by
very rapid multiple stimuli
C) the muscle twitch is prolonged and continuous while a tetanic contraction is brief and
"jerky"
D) the muscle twitch occurs only in small muscles while a tetanic contraction occurs in
large muscle groups
E) the muscle twitch is a brief and "jerky" movement, while the tetanic contraction is
prolonged and continuous
Answer: E
Diff: 3
Page Ref: 194
23) Creatine phosphate (CP) functions within the muscle cells by:
A) forming a temporary chemical compound with myosin
B) forming a chemical compound with actin
C) inducing a conformational change in the myofilaments
D) storing energy that will be transferred to ADP to resynthesize ATP as needed
E) storing energy that will be transferred to ATP to resynthesize ADP as needed
Answer: D
Diff: 2
Page Ref: 195
24) The condition of skeletal muscle fatigue can be best explained by:
A) the all-or-none law
B) the inability to generate sufficient quantities of ATP due to feedback regulation of
synthesis
C) insufficient intracellular quantities of ATP due to excessive consumption
D) a total lack of ATP
E) inadequate numbers of mitochondria
Answer: C
Diff: 1
Page Ref: 195-196
25) Which one of the following muscle actions would NOT be classified as an ISOTONIC
contraction:
A) pushing against a stationary wall
B) lifting a glass of water to your mouth
C) writing a letter
D) tying your shoe
E) throwing a ball
Answer: A
Diff: 1
Page Ref: 197
9
26) Anaerobic glycolysis occurs without:
A) ATP
B) oxygen
C) lactic acid
D) carbon dioxide
E) glucose
Answer: B
Diff: 3
Page Ref: 195
27) Which of these pathways to regenerate ATP during muscle activity is the fastest:
A) direct phosphorylation of ADP by creatine phosphate
B) aerobic respiration
C) anaerobic glycolysis and lactic acid formation
D) oxidative phosphorylation
E) both aerobic respiration and anaerobic glycolysis
Answer: C
Diff: 3
Page Ref: 195
28) The insertion of the gluteus maximus is the:
A) sacrum
B) tibia
C) ilium
D) calcaneus
E) femur
Answer: E
Diff: 2
Page Ref: 211
29) Which of the following muscles closes the jaw:
A) the buccinator
B) the masseter
C) the frontalis
D) the sternocleidomastoid
E) the masseter and the temporalis
Answer: E
Diff: 2
Page Ref: 207
30) Sandra is playing the piano for her recital. Which muscle is not involved in the movement of
her hands and/or fingers:
A) flexor carpi radialis
B) flexor carpi ulnaris
C) extensor digitorum
D) extensor digitorum longus
E) extensor carpi radialis
Answer: D
Diff: 2
Page Ref: 219
10
31) Which of the following muscles inserts on the calcaneus:
A) the semitendinosus
B) the sartorius
C) the tibialis anterior
D) the soleus
E) the iliopsoas
Answer: D
Diff: 2
Page Ref: 214; 219
32) Which one of the following does NOT compress the abdomen:
A) internal oblique
B) external oblique
C) transversus abdominis
D) latissimus dorsi
E) rectus abdominis
Answer: D
Diff: 2
Page Ref: 209
33) A muscle located on the ventral (anterior) side of the body is the:
A) pectoralis major
B) occipitalis
C) gastrocnemius
D) gluteus medius
E) latissimus dorsi
Answer: A
Diff: 1
Page Ref: 208
34) A nursing infant develops a powerful sucking muscle that adults also use for whistling or
blowing a trumpet called the:
A) platysma
B) masseter
C) zygomaticus
D) buccinator
E) temporalis
Answer: D
Diff: 1
Page Ref: 207
35) Which of these muscles is not responsibile for flexion or extension of the arm?
A) biceps brachii
B) triceps brachii
C) brachialis
D) platysma
E) latissimus dorsi
Answer: D
Diff: 3
Page Ref: 210; 211
11
36) A muscle group that works with and assists the action of a prime mover is a(n):
A) antagonist only
B) fixator only
C) synergist only
D) antagonist and synergist
E) antagonist and fixator
Answer: C
Diff: 1
Page Ref: 202
37) Which of the following muscles is not involved in dorsiflexion and/or plantar flexion of the
foot:
A) gastrocnemius
B) tibialis anterior
C) extensor digitorum longus
D) soleus
E) iliopsoas
Answer: E
Diff: 3
Page Ref: 212; 214
38) Which one of the following is the action of the orbicularis oris:
A) closes, purses, and protrudes the lips
B) pulls the lower lip down and back
C) draws the eyebrows together
D) allows blinking, squinting, and various other protective mechanisms for the eye
E) closes the jaw
Answer: A
Diff: 1
Page Ref: 207
39) Paralysis of which of the following would make an individual unable to flex the thigh:
A) biceps femoris
B) vastus medialis
C) vastus lateralis
D) vastus intermedius
E) iliopsoas and rectus femoris
Answer: E
Diff: 2
Page Ref: 212; 214
40) Which one of the following muscles is involved in abduction of the arm at the shoulder joint:
A) deltoid
B) biceps brachii
C) triceps brachii
D) latissimus dorsi
E) pectoralis major
Answer: A
Diff: 2
Page Ref: 210
12
41) Which of the following muscles adducts the thigh:
A) peroneus muscles
B) gluteus maximus
C) sartorius
D) quadriceps group
E) adductor muscles
Answer: E
Diff: 1
Page Ref: 214
42) While doing "jumping jacks" during an exercise class, your arms and legs move laterally
away from the midline of your body. This motion is called:
A) extension
B) flexion
C) abduction
D) adduction
E) circumduction
Answer: C
Diff: 1
Page Ref: 199
43) Which of the following muscles are antagonists:
A) biceps brachii and triceps brachii
B) bicpes femoris and biceps brachii
C) vastus medialis and vastus lateralis
D) masseter and temporalis
E) gastrocnemius and soleus
Answer: A
Diff: 3
Page Ref: 211
44) Paralysis of which of the following would make an individual unable to flex the knee:
A) hamstring muscle group
B) gluteal muscle group
C) gastrocnemius
D) sartorius
E) iliopsoas
Answer: A
Diff: 3
Page Ref: 214
45) Which one of the following is NOT a criteria generally used in naming muscles:
A) relative size of the muscle
B) number of origins of the muscle
C) shape of the muscle
D) method of attachment of the muscle to bone
E) action of the muscle
Answer: D
Diff: 2
Page Ref: 204
13
True/False
1) Skeletal muscle is considered involuntary because it is the only type of muscle usually
subject to conscious control.
Answer: FALSE
Diff: 1
Page Ref: 183; 185
2) The epimysium covers individual muscle fibers.
Answer: FALSE
Diff: 1
Page Ref: 185
3) Skeletal muscles need nerve stimulation for contraction to occur.
Answer: TRUE
Diff: 1
Page Ref: 189
4) A nerve cell and all the muscle cells that it stimulates are referred to as a motor unit.
Answer: TRUE
Diff: 1
Page Ref: 189
5) A contraction in which a skeletal muscle does not shorten but its tension increases is called
isometric.
Answer: TRUE
Diff: 1
Page Ref: 197
6) Cardiac muscle fibers are relatively short, tapering cells within a single centrally located
nucleus.
Answer: FALSE
Diff: 1
Page Ref: 186
7) The neurotransmitter used by the nervous system to activate skeletal muscle cells is
acetylcholine.
Answer: TRUE
Diff: 1
Page Ref: 189
8) Thick filaments are made of a protein called actin.
Answer: FALSE
Diff: 1
Page Ref: 189
9) One of the important functions of skeletal muscle is to generate heat.
Answer: TRUE
Diff: 1
Page Ref: 187
10) Lactic acid results from aerobic respiration.
Answer: FALSE
Diff: 2
Page Ref: 195
11) A sustained partial contraction of skeletal muscle is called muscle tone.
Answer: TRUE
Diff: 1
Page Ref: 197
14
12) An aponeurosis is a ropelike piece of muscle fascia that forms indirect connections to
muscles of the leg.
Answer: FALSE
Diff: 1
Page Ref: 185
13) A muscle twitch results when the muscle is stimulated so rapidly that no evidence of
relaxation is seen.
Answer: FALSE
Diff: 2
Page Ref: 194
14) The effect of the neurotransmitter on the muscle cell membrane is to temporarily modify its
permeability of ions such as Na+ and K+.
Answer: TRUE
Diff: 2
Page Ref: 189-190
15) 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.
Answer: TRUE
Diff: 2
Page Ref: 192
16) The insertion of the biceps brachii muscle is on the radius.
Answer: FALSE
Diff: 2
Page Ref: 211
17) A prime mover of the arm that acts in adduction is the deltoid.
Answer: FALSE
Diff: 1
Page Ref: 210
18) The deepest muscle of the abdominal wall is the transversus abdominis.
Answer: TRUE
Diff: 2
Page Ref: 209
19) Dorsiflexion and plantar flexion are synergistic actions.
Answer: FALSE
Diff: 1
Page Ref: 202
20) Plantar flexion at the ankle joint is accomplished by the tibialis anterior muscle.
Answer: FALSE
Diff: 2
Page Ref: 214
21) The bicpes brachii muscle is named for the two heads that orginiate from the shoulder
girdle.
Answer: TRUE
Diff: 2
Page Ref: 211
22) There are 206 skeletal muscles in the human body.
Answer: FALSE
Diff: 1
Page Ref: 198
23) Supination and pronation refer to up and down movements of the foot at the ankle.
Answer: FALSE
Diff: 2
Page Ref: 202
15
Matching
Match the following:
1) The distance between two Z
discs
Diff: 2
Page Ref: 187-188
2) Otherwise known as thick
filaments
Diff: 2
Page Ref: 189
B) myosin filaments
C) actin filaments
D) Z discs
3) Contains only the actin
filaments
Diff: 2
A) I band
E) sarcomere
Page Ref: 187-188
F) H zone
4) Both actin and myosin are
found in this band
G) A band
Diff: 1
Page Ref: 187-188
5) The type of filament that is
studded with myosin heads
Diff: 1
Page Ref: 189
6) Tiny contractile unit that
shortens during muscle
contraction
Diff: 2
Page Ref: 187; 192
7) Actin filaments are anchored
to these disclike membranes
Diff: 1
Page Ref: 189
8) Lighter central portion of the
A band
Diff: 2
1) E
7) D
Page Ref: 187
2) B
8) F
3) A
4) G
16
5) B
6) E
Match the following:
9) Serves as the actual "go"
signal for muscle contraction
Diff: 2
Page Ref: 193
B) acetylcholine
10) Neurotransmitter substance
released at motor end plates
by the motor neuron
Diff: 2
F) aerobic respiration
Page Ref: 189
G) anaerobic respiration
12) A metabolic pathway that
produces water, carbon
dioxide, and ATP, and
provides for a large amount
of ATP per glucose because
oxygen is used
Diff: 3
C) enzymes
D) potassium ions
E) calcium ions
Page Ref: 189
11) Normally stored in the
sarcoplasmic reticulum
Diff: 2
A) creatine phosphate
H) sodium ions
Page Ref: 195
13) A reserve, high-energy
compound used to convert
ADP to ATP by the transfer
of a high-energy phosphate
group
Diff: 2
Page Ref: 195
14) Destroys acetylcholine (ACh)
Diff: 2
9) E
Page Ref: 190
10) B
11) E
12) F
17
13) A
14) C
Match the following:
15) Type of movement that
decreases the angle of the
joint
Diff: 2
Page Ref: 199
16) Type of movement that
results when the forearm
rotates laterally so that the
palm faces anteriorly
Diff: 2
Page Ref: 202
17) The movement of a limb
toward the body midline
Diff: 2
A) supination
B) extension
C) pronation
D) rotation
E) adduction
F) flexion
G) abduction
Page Ref: 199
18) Type of movement that
increases the angle of the
joint
Diff: 2
Page Ref: 199
19) The movement of a bone
around its longitudinal axis
Diff: 2
Page Ref: 199
20) The movement of a limb
away from the body midline
Diff: 2
Page Ref: 199
21) Type of movement that
results when the forearm
rotates medially so the palm
faces posteriorly
Diff: 2
Page Ref: 202
22) Primary action of the deltoid
Diff: 2
Page Ref: 210
23) Primary action of the
adductor muscles
Diff: 2
Page Ref: 214
24) Primary action of the erector
spinae
Diff: 2
Page Ref: 210
25) Primary action of the rectus
abdominis
Diff: 2
Page Ref: 209
18
15) F
21) C
16) A
22) G
17) E
23) E
18) B
24) B
19) D
25) F
20) G
Essay
1) Compare skeletal, smooth, and cardiac muscles as to their body location, microscopic
anatomy, regulation of contraction, speed of contraction, and rhythmicity.
Answer: Body location—skeletal muscle is attached to bones or to skin (some facial muscles);
cardiac muscle is located in the walls of the heart; smooth muscle is found in the walls
of hollow visceral organs (other than the heart).
Microscopic anatomy—skeletal muscle consists of very long, cylindrical,
multinucleated cells with very obvious striations; cardiac muscle consists of branching
chains of cells that are uninucleated and possess striations; smooth muscle consists of
single fusiform uninucleated cells that lack striations.
Regulation of contraction—skeletal muscle is voluntary via nervous system controls,
but this normal voluntary control can be overridden by involuntary reflex arcs (as
explained in later chapters); cardiac muscle is involuntary via the heart pacemaker,
nervous system controls, and hormones; smooth muscle is involuntary via nervous
system controls, hormones, other chemicals, and stretching.
Speed of contraction—skeletal muscle is slow to fast; cardiac muscle is slow; smooth
muscle is the slowest.
Rhythmicity—skeletal muscle is arrhythmic; cardiac muscle is rhythmic; smooth
muscle is sometimes rhythmic.
Diff: 3
Page Ref: 183-186
2) Describe the events that occur from the time that a motor neuron releases acetylcholine at
the neuromuscular junction until muscle cell contraction occurs.
Answer: Acetylcholine is released, which diffuses through the synaptic cleft and attaches to
receptors on the sarcolemma. The sarcolemma permeability to sodium ions increases
briefly, causing sodium ions to rush into the muscle cell, which changes the electrical
conditions of the resting sarcolemma. An action potential is initiated and sweeps over
the entire sarcolemma. Calcium ions are released from storage areas inside the
sarcoplasmic reticulum of the muscle cell. They attach to the myofilaments, which
triggers the sliding of the myofilaments and causes a muscle cell contraction.
Diff: 3
Page Ref: 189-192
3) List the seven criteria that are used in naming muscles and give an example of each.
Answer: 1. Direction of the muscle fibers (e.g., external oblique)
2. Relative size of the muscle (e.g., maximus, minimus, longus)
3. Location of the muscle (e.g., temporalis, frontalis)
4. Number of origins (e.g., biceps, triceps, quadriceps)
5. Location of the muscle's origin and insertion (e.g., the sternocleidomastoid muscle
has its origin on the sternum [sterno] and clavicle [cleido] and inserts on the mastoid
process of the temporal bone)
6. Shape of the muscle (e.g., the deltoid muscle is roughly triangular—deltoid means
"triangular")
7. Action of the muscle (e.g., the adductor muscles of the thigh all bring about its
adduction, and the extensor muscles of the wrist all extend the wrist)
Diff: 3
Page Ref: 202; 204
19
4) What is the effect of aging on skeletal muscles?
Answer: With aging, the amount of connective tissue in muscle increases and the amount of
skeletal muscle tissue decreases, thus the muscles become stringier (more sinewy).
Since skeletal muscle represents a larger portion of body weight, it begins to decline in
elderly persons as this normal loss of muscle mass occurs. Another result of the loss in
muscle mass is a decrease in muscle strength—strength decreases by about 50% by the
age of 80. Regular exercise can help offset the effects of aging on the muscular system,
and frail elders who begin to "pump iron" can rebuild muscle mass and significantly
increase their functional strength.
Diff: 3
Page Ref: 221
5) Explain the steps in the sliding filament theory of muscle contraction, following the
spreading of an action potential along the sarcolemma.
Answer: An action potential triggers the sarcoplasmic reticulum to release calcium ions into the
sarcoplasm of the muscle cell. The calcium ions bind to regulatory proteins on the
actin filaments, changing both their shape and their position on the actin filaments.
This action allows myosin receptor sites on the thin actin filaments to become
exposed. The myosin heads attach to the myosin binding sites on the actin filaments.
Energized by ATP, the myosin heads swivel toward the center of the sarcomere,
attaching and detaching several times. In the process the thin actin filaments are
pulled toward the center of the sarcomere. As this event occurs simultaneously in
sarcomeres throughout the cell, the muscle cell shortens. When the action potential
ends, the calcium ions are reabsorbed back into the sarcoplasmic reticulum storage
areas, causing the regulatory proteins to resume their original shape and position.
Since the myosin heads now have nothing to attach to, the muscle cell relaxes and
returns to its original length.
Diff: 3
Page Ref: 192-193
6) Fascicle arrangements produce skeletal muscles with different structures and functional
properties, and determine their individual range of motion and power. List the seven
different fascicle arrangements of human skeletal muscles and give a specific example of
each:
Answer: 1. Circular—orbicularis oris, orbicularis oculi
2. Convergent—pectoralis major
3. Parallel—sartorius
4. Unipennate—extensor digitorum longus
5. Multipennate—deltoid
6. Fusiform—biceps brachii
7. Bipennate—rectus femoris
Diff: 3
Page Ref: 204-206
7) List the "five golden rules" of gross skeletal muscle activity.
Answer: 1. With few exceptions, all muscles cross at least one joint.
2. Typically, the bulk of the muscle lies proximal to the joint crossed.
3. All muscles have at least two attachments: the origin and the insertion.
4. Muscles can only pull: they never push.
5. During contraction, the muscle insertion moves toward the origin.
Diff: 3
Page Ref: 198
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8) Explain how isometric and isotonic contractions differ, using examples of each.
Answer: 1. Isometric contractions are contractions in which the muscles do not shorten. An
example of an isometric contraction is pushing against a wall with bent elbows. The
muscles cannot shorten since the wall doesn't move.
2. Isotonic contractions occur when muscles shorten and movement occurs due to the
sliding of the myofilaments. Flexion and extension of the arm are just two examples of
isotonic contractions.
Diff: 2
Page Ref: 197
9) Explain the difference between a motor unit and a neuromuscular junction.
Answer: 1. The motor unit is the one neuron and all of the skeletal muscle cells it stimulates.
2. The neuromuscular junction occurs between the axon terminals of one neuron and
the sarcolemma of a skeletal muscle cell.
Diff: 2
Page Ref: 189
10) Explain how muscle movements mature in a baby, using examples of each.
Answer: 1. Muscle development proceeds in a cephalic/caudal direction. For instance, babies
can raise their heads before they can walk.
2. Muscle control proceeds in a proximal/distal direction. For instance, babies can
perform gross movements like wave "bye-bye" before they can use the pincher grasp
to pick up a pin.
Diff: 2
Page Ref: 221
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