Deck 8: Muscle Physiology

Question 1

Myosin

A)is found in the A band
B)is found in the I band
C)is in the thin filaments
D)shortens during muscle contraction because it is one of the contractile proteins
E)is found in the Z line

Answer 1

A

Question 2

Actin

A)has ATPase activity
B)are spherical
C)forms a helical chain that forms the main structural component of the thin filaments
D)has characteristics a and b
E)has characteristics b and c

Answer 2

E

Question 3

Myosin is

A)found in the I band
B)attached to tropomyosin
C)a regulatory protein
D)all of the above
E)none of the above

Answer 3

E

Question 4

Thick filaments in skeletal muscle are composed of

A)actin
B)troponin and tropomyosin
C)myosin
D)all of the above
E)only b and c

Question 5

Z lines

A)are formed by the T tubules
B)extend down the middle of the I band
C)are formed by cross bridges
D)are part of the thin filaments
E)extend down the middle of the sarcomere

Question 6

Troponin

A)binds with calcium to allow sarcomere shortening
B)breaks down myosin cross bridges
C)is an enzyme in the sarcomere
D)forms the boundaries of a sarcomere
E)has an ATPase site

Question 7

Skeletal muscle fibers

A)have T tubules within their sarcomeres
B)have Z lines extending down the middle of the I bands
C)contain gap junctions
D)have all of the above characteristics
E)have characteristics b and c

Question 8

The region between two Z lines is a

A)muscle fiber
B)myofibril
C)myofilament
D)sarcomere
E)sarcoplasmic reticulum

Question 9

Order the following muscle cell components from larger to smaller
1)troponin
2)myofibril
3)sarcomere
4)thin filament
5)muscle fiber

A)3, 4, 1, 5, 2
B)1, 2, 3, 5, 4
C)5, 4 ,3 , 1, 2
D)5, 2, 3, 4, 1
E)3, 4, 5, 2, 1

Question 10

Skeletal muscle fibers

A)are some of the longest cells in the body
B)are attached end-to-end within a muscle
C)contain Z lines within their A bands
D)contain only one nucleus
E)exhibit characteristics b and c

Question 11

Identify the characteristic(s) shared by all types of muscle tissues?

A)They are neurogenic.
B)They have T tubules.
C)They have tropomyosin.
D)They attach to tendons.
E)They have neuromuscular junctions.

Question 12

The functional unit of skeletal muscle

A)is the smallest contractile component of a muscle fiber
B)is the area between two Z lines
C)is the sarcomere
D)contains only one A band
E)exhibits all of the above characteristics

Question 13

Sarcomeres are arranged end to end as

A)Z lines
B)myofibrils
C)T tubules
D)myofilaments
E)cross bridges

Question 14

A function of tropomyosin is

A)to bind Ca₂₊
B)to form attachments with myosin cross bridges
C)to prevent myosin cross bridges from attaching to the thin filaments
D)to act as an ATPase
E)none of the above

Question 15

Each I band in a skeletal muscle fiber includes

A)overlapping thin and thick filaments
B)thick filaments and one Z disc
C)thin filaments and one Z disc
D)thin filaments and two Z discs
E)actin, troponin, tropomyosin and two Z discs

Question 16

The striated appearance of skeletal muscle is due to the

A)orderly arrangement of the T tubules
B)orderly arrangement of the lateral sacs of the sarcoplasmic reticulum
C)orderly arrangement of the thick and thin filaments into A and I bands
D)orderly arrangement of the motor units
E)presence of white and red muscle fibers within the muscle

Question 17

Muscle fibers develop tension by

A)contraction of sarcomeres
B)shortening
C)the pushing of myosin by actin
D)all of the above
E)both a and b

Question 18

Actin

A)does not perform a power stroke during muscle contraction
B)contains a globular head that forms a cross bridge between the thick and thin filaments
C)is not found within A bands
D)is inhibited by Ca₂₊
E)does not attach to the Z lines

Question 19

Cross bridges

A)bind to actin during muscle contraction
B)are globular heads made of myosin
C)do not bend during muscle contraction
D)have characteristics a and b
E)have characteristics b and c

Question 20

During contraction of a sarcomere,

A)the Z discs move farther apart
B)the A bands become thicker
C)the I bands become narrower
D)the thin filaments become shorter
E)events c and d occur

Question 21

During contraction of skeletal muscle fibers, the

A)contractile proteins shorten
B)thin filaments slide inward toward the A band's center as a result of cycles of cross-bridge binding and bending
C)thick and thin filaments become tightly coiled, thus shortening the sarcomere
D)I bands slide in between the A bands
E)lateral sacs of the sarcoplasmic reticulum shorten, pulling the Z lines closer together

Question 22

During a cross-bridge cycle in skeletal muscle,

A)the cross bridge is energized when it splits ATP into ADP and P
B)the cross bridge must bind with ATPase before a power stroke will occur
C)Ca₂₊ causes tropomyosin to move off of the myosin's actin-binding sites
D)ADP binds to the cross bridge at the end of the power stroke
E)both a and b occur

Question 23

Binding of ____ to myosin permits the cross-bridge to ____.

A)ATP; bind with actin
B)ATP; detach from actin
C)calcium; bind with actin
D)calcium; detach from actin
E)None of the above correctly complete the sentence.

Question 24

During contraction, asynchronous cycling of cross bridges

A)prevents tetany
B)prevents thick filaments from slipping backwards
C)prevents thin filaments from slipping backwards
D)utilizes less ATP
E)does not do any of the above

Question 25

Which statement is not true about cross bridges?

A)They are a component of thin filaments.
B)They are comprised of myosin.
C)They have an actin binding site.
D)They have an ATPase binding site.
E)They provide power stroking.

Question 26

An action potential rapidly spreads to the central portions of a muscle cell by means of

A)Z lines
B)sarcoplasmic reticulum
C)T tubules
D)lateral sacs
E)both a and c

Question 27

The T tubules

A)store Ca₂₊
B)provide a means of rapidly transmitting the action potential from the surface into the central portions of the muscle fiber
C)store ATP
D)run longitudinally between the myofibrils
E)have expanded lateral sacs

Question 28

Which of the following are involved in the regulation of cross bridge attachment activity?

A)calcium ions
B)troponin
C)tropomyosin
D)all of the above
E)only b and c

Question 29

Cross bridge interaction between actin and myosin in skeletal muscle is directly blocked by

A)acetylcholine
B)triads
C)Z lines
D)calcium
E)tropomyosin

Question 30

Which of the following changes in banding pattern occur during muscle relaxation?

A)Thin filaments move away from the Z lines.
B)I bands get wider.
C)H zones get narrower.
D)Thick filaments become longer.
E)Both b and c occur.

Question 31

According to the sliding-filament mechanism, the

A)A bands slide between the I bands
B)thin filaments slide inward toward the center of the A band
C)Z lines slide between the T tubules
D)contractile proteins shorten, thus shortening the sarcomere
E)filaments slide past the lateral sacs of the sarcoplasmic reticulum

Question 32

The H zone

A)is the area within the middle of the A band where the thin filaments do not reach
B)shortens or disappears during contraction
C)contains only thick filaments
D)does not contain cross bridges
E)is all of the above

Question 33

Foot proteins

A)span the gap between a lateral sac of the sarcoplasmic reticulum and a T tubule
B)are believed to serve as Ca₂₊ channels
C)bind to and pull the thin filaments inward toward the A band's center during contraction
D)have characteristics a and b
E)are none of the above

Question 34

During excitation-contraction coupling,

A)the action potential travels down the T tubules
B)Ca₂₊ is released from the sarcoplasmic reticulum
C)Ca₂₊ is taken up by the sarcoplasmic reticulum
D)both a and b occur
E)both a and c occur

Question 35

During muscle contraction,

A)the Z lines move farther away from the thick filaments
B)the A band becomes narrower
C)the H zone becomes narrower or disappears
D)the I band remains unchanged
E)both b and c occur

Question 36

The T tubules

A)store Ca₂₊
B)provide a means of rapidly transmitting ACh to the central portions of the muscle fiber
C)provide attachment sites for ACh
D)perform b and c
E)do not do any of the above

Question 37

The sarcoplasmic reticulum stores ____ when a muscle is relaxed and releases it for binding to ____ during contraction.

A)calcium; troponin
B)calcium; tropomyosin
C)sodium; tropomyosin
D)potassium; tropomyosin
E)sodium; troponin

Question 38

Of the steps in excitation-contraction below, which step occurs before the others?

A)Exposed actin sites bind with myosin cross bridges.
B)Sodium channels open in the fiber's membrane.
C)Calcium is released from the sarcoplasmic reticulum.
D)Troponin binds calcium.
E)Attachment of ATP allows for cross bridge detachment.

Question 39

Which statement is incorrect about cross bridges?

A)They are globular myosin heads that protrude from the thick filaments.
B)They bend during muscle contraction.
C)They attach and detach from actin during muscle contraction.
D)They are not found in the I band.
E)They bind with troponin during contraction.

Question 40

Sequence the following events involved in muscle cell contraction:
1)Sodium channels open and sodium flows in.
2)Impulse reaches the axon's terminal.
3)ACh binds to receptors on the muscle cell membrane.
4)Synaptic vesicles fuse with neuron's membrane and release ACh via exocytosis.
5)If enough sodium moves in to the muscle cell, an impulse (action potential) develops.

A)1, 2, 3, 4, 5
B)2, 1, 3, 4, 5
C)2, 4, 3, 1, 5
D)3, 4, 5, 1, 2
E)3, 5, 2, 1, 4

Question 41

Twitch summation

A)is a means by which gradation of muscle contraction may be accomplished
B)results from the additional release of Ca₂₊ within the cytosol of muscle fibers
C)results from increasing the frequency at which motor units are firing within a muscle
D)results from more cross bridges binding to actin within muscle fibers
E)has all of the above characteristics

Question 42

In twitch summation, the muscle fiber

A)is stimulated again before the fibers returns to resting potential.
B)is stimulated again before it completely returns to resting position.
C)contracts stronger but stronger action potentials do not occur.
D)experiences a and b
E)experiences b and c

Question 43

To pick up something heavier than your pencil, your nervous system could

A)stimulate larger motor units
B)decrease the frequency of stimulation to allow a more prolonged contraction to occur
C)decrease the refractory periods
D)block acetylcholinesterase at the neuromuscular junction to allow acetylcholine to function longer
E)do all of the above

Question 44

Submaximal isometric contractions are important for

A)moving large objects
B)walking
C)maintaining posture
D)writing
E)both a and b

Question 45

Picking up a book at a constant speed requires that

A)muscle tension be equal to the book's weight
B)the muscle perform an eccentric contraction
C)the muscle perform an isometric contraction
D)the muscle perform a concentric contraction
E)both a and d occur

Question 46

A lack of ATP in a contracted skeletal muscle cell would most likely cause

A)cross bridges to detach from actin
B)the sarcomeres to remain shortened
C)an inability to relax
D)both a and c
E)both b and c

Question 47

A motor unit refers to

A)a single motor neuron plus all of the muscle fibers it innervates
B)a single muscle fiber plus all of the motor neurons that innervate it
C)all of the motor neurons supplying a single muscle
D)a pair of antagonistic muscles
E)a sheet of smooth muscle cells connected by gap junctions

Question 48

In a muscle fiber undergoing maximal tetanic stimulation, the velocity of shortening ____ as the load ____.

A)decreases; decreases
B)decreases; increases
C)increases; increases
D)remains constant; increases
E)remains constant; decreases

Question 49

Which of the following is involved in muscle relaxation?

A)Acetylcholinesterase removes ACh and the muscle cell returns to resting potential.
B)Ca₂₊ is actively taken up by the lateral sacs when there is no longer an action potential.
C)The cross bridges pull the filaments back to their original resting positions.
D)Both a and b
E)Both b and c

Question 50

Based on the length-tension relationship,

A)stretching a skeletal muscle 30% longer than the lo results in a greater contraction
B)varying the amount of overlap of thick and thin filaments does not greatly affect contraction force as long as tension remains the same
C)more tension develops if a muscle is 30% shorter than its resting length
D)muscle tension remains the same as long as the muscle's length is not more than 30% of the resting length.
E)a resting muscle that is shorter or longer than its lo will generate less tension at the onset of contraction.

Question 51

Muscles developing tension while lengthening are performing ____ contractions.

A)concentric
B)eccentric
C)isometric
D)fatiguing
E)oscillating

Question 52

With eccentric muscle contractions,

A)development of tension occurs at constant muscle length
B)muscles lengthen while contracting
C)muscles shorten while contracting
D)muscle length and tension vary throughout a range of motion
E)none of the above occur

Question 53

The energy for cross bridge cycling during muscle contraction is provided by:

A)acetylcholine
B)Ca₂₊
C)ATP
D)myosin
E)actin

Question 54

Twitch summation

A)results from increases in cytosolic calcium levels
B)results from pumping of calcium into the sarcoplasmic reticulum
C)can be enhanced by allowing a cell to completely relax
D)rarely results in tetany
E)is not characterized by any of the above

Question 55

Whole muscle tension depends on all of the following except

A)number of muscle fibers contracting
B)tension produced by each contracting fiber
C)extent of motor-unit recruitment
D)frequency of stimulation
E)the proportion of each motor unit used at any given time

Question 56

Which of the following is involved in the relaxation of a muscle cell?

A)Synthesis of ACh by acetylcholinesterase
B)Initiation of action potentials
C)The troponin-tropomyosin complex slipping back into its blocking position
D)Detachment of actin from tropomyosin
E)T tubules actively absorbing Ca₂₊

Question 57

Muscle tension

A)is created when tension generated by sarcomeres is transmitted via the connective tissue and tendons to the bones
B)is the force exerted on a muscle by the weight of an object
C)is greater than the load during an isometric contraction
D)is all of the above
E)is none of the above

Question 58

During an isotonic contraction,

A)sarcomeres do not shorten in the muscle
B)movement does not occur inside the muscle
C)the muscle does not change length
D)the muscle's tension does not overcome a load
E)the muscle's tension remains constant

Question 59

During an isometric contraction, the muscle

A)maintains a constant tension
B)shortens
C)moves a body part
D)maintains a constant length
E)tension is greater than the load

Question 60

The origin of a muscle is its

A)main, thickest part
B)middle, thinner part
C)movable end of attachment
D)source of development in the fetus
E)stationary end of attachment

Question 61

The corticospinal system

A)consists of fibers originating in the primary motor cortex and terminating on motor neurons
B)involves the motor regions of the cortex, cerebellum, basal nuclei, and thalamus
C)is primarily concerned with regulation of body posture
D)has characteristics a and b
E)has characteristics b and c

Question 62

Energy sources available to form ATP in muscle fibers in the absence of oxygen include

A)creatine phosphate
B)chemiosmosis
C)glycolysis
D)creatine phosphate and glycolysis
E)chemiosmosis and glycolysis

Question 63

Fast-glycolytic (type IIx) muscle fibers

A)have high myosin-ATPase activity
B)can carry out oxidative phosphorylation
C)fatigue rapidly
D)contain myoglobin
E)have all of the above characteristics

Question 64

Which of the following does not directly influence motor neurons?

A)primary motor cortex
B)cerebellum
C)brain stem
D)afferent neurons (through intervening interneurons)
E)None of the above

Question 65

During aerobic exercise, the primary means for ATP production in muscle fibers involves

A)creatine phosphate
B)fermentation
C)oxidative phosphorylation
D)glycolysis
E)myoglobin

Question 66

Muscular fatigue can be caused by

A)lactic acid accumulation
B)depletion of ATP
C)depletion of ACh
D)only two of the above
E)a, b, or c

Question 67

Fast-oxidative (type IIa) fibers

A)contain very few mitochondria
B)can be converted into fast-glycolytic fibers by regular resistance activities
C)are most abundant in muscles specialized for maintaining low-intensity contractions for long periods of time without fatigue
D)have characteristics b and c
E)have none of the above characteristics

Question 68

Conscious initiation of muscle contraction is controlled by

A)the spinal cord
B)the brain stem
C)the cerebral cortex
D)the thalamus
E)none of the above

Question 69

When a muscle atrophies, its muscle fibers

A)split lengthwise
B)decreases in mass and becomes weaker
C)increase in diameter
D)undergo mitotic cell division
E)dissolve and are replaced by fibrous scar tissue

Question 70

If the load on a muscle is increased, eventually a load will be reached at which the velocity of shortening becomes zero.At this point, the muscle contraction is referred to as

A)concentric
B)eccentric
C)isotonic
D)isokinetic
E)isometric

Question 71

With the type of lever system exemplified by flexion of the elbow joint, when an object is held in the hand, the

A)power arm of the lever is the distance between the elbow joint and the insertion of the biceps muscle
B)load arm of the lever is the distance between the elbow joint and the hand
C)velocity and distance moved by the hand is amplified at the expense of the biceps muscle having to exert considerably greater force than the actual load that is moved
D)answers a, b, and c are correct
E)answers a and b are the only correct answers

Question 72

Select the correct statement about the summation of simple twitches.

A)They can occur because of the long duration of the action potential in a muscle fiber.
B)They reduce the tension in a muscle.
C)They result from the slow stimulation of a muscle fiber.
D)The effect is unrelated to the refractory periods of action potentials.
E)The twitches resulting from separate action potentials.

Question 73

Which statement below is characteristic of most of the body's lever systems?

A)They work at mechanical advantage.
B)They work at a mechanical disadvantage.
C)Muscles must exert greater forces than the load.
D)Both a and b
E)Both b and c

Question 74

Myoglobin

A)can store small amounts of O₂
B)increases the rate of O₂ transfer from the blood into muscle fibers
C)is abundant in fast-glycolytic fibers
D)can perform a and b
E)has characteristics a and c

Question 75

Which of the following statements about the different types of muscle fibers is incorrect?

A)The higher the ATPase activity, the faster the speed of contraction.
B)Muscles with a high glycolytic capacity and large glycogen stores are more resistant to fatigue.
C)Muscles with high ATP-synthesizing ability are more resistant to fatigue.
D)Oxidative types of muscle fibers contain myoglobin.
E)Muscle fibers containing large amounts of myoglobin have a dark red color in comparison to the paler fibers, which have little myoglobin.

Question 76

Fatigue is the failure of a muscle fiber to maintain ____ as a result of previous contractile activity.

A)excitability
B)muscle mass
C)tension
D)sarcomere number
E)mitochondria

Question 77

The first means by which ATP is produced at the onset of contractile activity is

A)transfer of energy and phosphate from creatine phosphate to ADP
B)oxidative phosphorylation
C)glycolysis
D)degradation of myoglobin
E)none of these

Question 78

The muscle cells of a marathon runner's legs would exhibit all these characteristics except

A)high resistance to fatigue
B)low myoglobin content
C)low glycogen content
D)many mitochondria
E)slow speed of contraction

Question 79

In the body's lever systems, the fulcrums are represented by the

A)joints
B)long bones
C)tendons
D)short bones
E)skeletal muscles

Question 80

Enlargement of muscle due to weight lifting is primarily a result of

A)enlargement of individual myofilaments
B)hyperplasia
C)increased production of actin and myosin
D)increases in the number of cells
E)Both b and d