chapter_6_answers.pdf

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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

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Figure 6.2

Using Figure 6.2, match the following:

5) The connective tissue "overcoat" that wraps the entire muscle is indicated by letter

__________.


6) The connective tissue that wraps a fascicle, or bundle of muscle fibers, is indicated by letter

__________.


7) The muscle fiber is indicated by letter __________.


8) The endomysium that wraps individual muscle fibers is indicated by letter __________.


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

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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

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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

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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


5) Which of the following does not describe cardiac muscle tissue:

A) uninucleate

B) striations

C) involuntary

D) rhythmic contractions

E) attached to bones


6) What type of membrane wraps a fascicle:

A) endomysium

B) epimysium

C) aponeuroses

D) perimysium

E) tendons


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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


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


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


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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


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


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


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


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


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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


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


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


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


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

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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


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


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


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26) Anaerobic glycolysis occurs without:

A) ATP

B) oxygen

C) lactic acid

D) carbon dioxide

E) glucose


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


28) The insertion of the gluteus maximus is the:

A) sacrum

B) tibia

C) ilium

D) calcaneus

E) femur


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


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


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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


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


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


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

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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


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


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


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41) Which of the following muscles adducts the thigh:

A) peroneus muscles

B) gluteus maximus

C) sartorius

D) quadriceps group

E) adductor muscles


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


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


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


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


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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.


5) A contraction in which a skeletal muscle does not shorten but its tension increases is called

isometric.


6) Cardiac muscle fibers are relatively short, tapering cells within a single centrally located

nucleus.


7) The neurotransmitter used by the nervous system to activate skeletal muscle cells is

acetylcholine.


8) Thick filaments are made of a protein called actin.


9) One of the important functions of skeletal muscle is to generate heat.


10) Lactic acid results from aerobic respiration.


11) A sustained partial contraction of skeletal muscle is called muscle tone.


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12) An aponeurosis is a ropelike piece of muscle fascia that forms indirect connections to

muscles of the leg.


13) A muscle twitch results when the muscle is stimulated so rapidly that no evidence of

relaxation is seen.


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.


16) The insertion of the biceps brachii muscle is on the radius.


17) A prime mover of the arm that acts in adduction is the deltoid.


18) The deepest muscle of the abdominal wall is the transversus abdominis.


19) Dorsiflexion and plantar flexion are synergistic actions.


20) Plantar flexion at the ankle joint is accomplished by the tibialis anterior muscle.


21) The bicpes brachii muscle is named for the two heads that orginiate from the shoulder

girdle.


22) There are 206 skeletal muscles in the human body.


23) Supination and pronation refer to up and down movements of the foot at the ankle.


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Matching

Match the following:

1) The distance between two Z

discs

A) I band

Diff: 2 Page Ref: 187-188 B) myosin filaments

2) Otherwise known as thick

filaments

C) actin filaments

Diff: 2 Page Ref: 189 D) Z discs

3) Contains only the actin

filaments

E) sarcomere

Diff: 2 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 Page Ref: 187

1) E 2) B 3) A 4) G 5) B 6) E

7) D 8) F

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9) Serves as the actual "go"

signal for muscle contraction

A) creatine phosphate

Diff: 2 Page Ref: 193 B) acetylcholine

10) Neurotransmitter substance

released at motor end plates

by the motor neuron

C) enzymes

D) potassium ions Diff: 2 Page Ref: 189 E) calcium ions

11) Normally stored in the

sarcoplasmic reticulum

F) aerobic respiration

Diff: 2 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

H) sodium ions

Diff: 3 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 Page Ref: 190

9) E 10) B 11) E 12) F 13) A 14) C

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15) Type of movement that

decreases the angle of the

joint

A) supination

B) extension Diff: 2 Page Ref: 199 C) pronation


results when the forearm

rotates laterally so that the

palm faces anteriorly

D) rotation

E) adduction Diff: 2 Page Ref: 202 F) flexion

17) The movement of a limb

toward the body midline

G) abduction



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


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

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15) F 16) A 17) E 18) B 19) D 20) G

21) C 22) G 23) E 24) B 25) F

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 locationskeletal 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 anatomyskeletal 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 contractionskeletal 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 contractionskeletal muscle is slow to fast; cardiac muscle is slow; smooth

muscle is the slowest.

Rhythmicityskeletal 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 triangulardeltoid 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

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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 strengthstrength 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. Circularorbicularis oris, orbicularis oculi

2. Convergentpectoralis major

3. Parallelsartorius

4. Unipennateextensor digitorum longus

5. Multipennatedeltoid

6. Fusiformbiceps brachii

7. Bipennaterectus 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.


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