Deck 12: Muscle: Mechanisms of Contraction and Neural Control

Question 1

The biceps brachii causes flexion of the elbow.The triceps brachii causes extension of the elbow,so it would be a/an

A)abductor.
B)antagonist.
C)agonist.
D)levator.

Answer 1

B

Question 2

Skeletal muscles with a low innervation ratio have a low degree of neural control.

Answer 2

False

Question 3

The light band of a skeletal muscle is known as the

A)A band.
B)Z disc.
C)I band.
D)H banD.

Answer 3

C

Question 4

The specialized region of the sarcolemma at the neuromuscular junction is called the

A)syncytium.
B)varicosity.
C)fascicle.
D)motor end plate.

Question 5

Skeletal muscle cells are multinucleated.This is called a/an

A)myoblast.
B)striation.
C)syncytium.
D)endomysium.

Question 6

The origin is the point of muscle attachment that is most stationary.

Question 7

The more movable bony attachment is the

A)flexor.
B)origin.
C)extensor.
D)insertion.

Question 8

Duchenne's muscular dystrophy

A)is an X-linked recessive trait.
B)most often affects women.
C)involves degeneration of the smooth muscle dense bodies.
D)All apply.

Question 9

Longer,stronger muscles have motor units with very few fibers.

Question 10

The prime mover of any skeletal movement is called the

A)flexor.
B)agonist.
C)abductor.
D)antagonist.

Question 11

The deadly botulinum toxin can be used in the cosmetic treatment of skin wrinkles because it produces a flaccid paralysis.

Question 12

Flexors increase the angle at a joint.

Question 13

Motor unit recruitment allows for _________ contraction strength.

A)increased
B)decreased
C)no change in

Question 14

The epimysium surrounds the individual muscle cells.

Question 15

A muscle that constricts an opening is a/an

A)extensor.
B)levator.
C)antagonist.
D)sphincter.

Question 16

Z discs are found bisecting the A bands.

Question 17

Each fascicle of a muscle is surrounded by the

A)perimysium.
B)epimysium.
C)endomysium.
D)sarcolemma.

Question 18

Muscles which move a limb away the midline of the body are termed as

A)abductor muscles.
B)adductor muscles.
C)extensor muscles.
D)flexor muscles.

Question 19

When skeletal muscle cells contract,they increase in length.

Question 20

Which of the following is needed for the myosin head to undergo a power stroke?

A)release of P_i
B)binding of ATP to the head
C)splitting of ATP into ADP and P_i
D)addition of Ca²⁺ to the head

Question 21

During skeletal muscle contraction,adjacent _________ are pulled closer together as the _______ between them shorten.

A)A bands;I bands
B)I bands;A bands
C)Z disks;A bands
D)Z disks;M lines

Question 22

Thin filaments are composed of myosin and tropomyosin.

Question 23

What protein primarily makes up the thin filament?

A)actin
B)myosin
C)titin
D)Z-discs

Question 24

Subunits of skeletal muscle cells that are composed of sarcomeres are called

A)myofibrils.
B)myofilaments.
C)sarcolemmas.
D)transverse tubules.

Question 25

During skeletal muscle contraction the A band decreases in size.

Question 26

What structure is composed of protein filaments and is located in the center of the thick filaments?

A)Z disk
B)titin
C)M line
D)actin

Question 27

What enzyme is needed to start the cross bridging process?

A)creatine phosphatase
B)kinase
C)myosin ATPase
D)Ca²⁺ATPase

Question 28

What muscle structural and functional unit runs from Z disc to Z disc?

A)A band
B)I band
C)sarcomere
D)myofibril

Question 29

What protein primarily makes up the thick filament?

A)actin
B)myosin
C)titin
D)troponin

Question 30

Myosin contains binding sites for ______________ and _____________.

A)sodium,calcium.
B)troponin,ATP.
C)ATP,actin.
D)actin,calcium.

Question 31

Myosin will not bind to actin unless ADP is bound to the myosin head.

Question 32

Cross-bridge formation occurs when myosin heads attach to actin molecules located in the thin filaments.

Question 33

The thick filament is also called the

A)A band.
B)I band.
C)H band.
D)M line.

Question 34

What is the lighter area in the center of the A-band called?

A)M-line
B)titin
C)Z-disc
D)H band

Question 35

Each somatic motor neuron with all the muscle fibers it innervates is a

A)fascicle.
B)varicosity.
C)motor unit.
D)sarcolemma.

Question 36

What structure runs the length of the sarcomere and contributes to the elastic recoil in muscle?

A)Z disk
B)titin
C)M line
D)actin

Question 37

Sarcomeres contain elastic titin filaments which help the muscles return to their resting length during muscle relaxation.

Question 38

Somatic motor neurons release the neurotransmitter _________ at the neuromuscular junction.

A)dopamine
B)acetylcholine
C)norepinephrine
D)serotonin

Question 39

The thick filament is split by a Z disc.

Question 40

The pumps that actively transport calcium back into the _______ are called Ca²⁺ -ATPase pumps.

A)transverse tubules
B)sarcoplasmic reticulum
C)neuromuscular junction
D)None apply.

Question 41

What is the role of ATP in muscle contraction and relaxation?

A)It is hydrolyzed from the myosin head to attach to actin.
B)It causes myosin head to detach from actin.
C)It powers the Ca²⁺ pumps to return Ca²⁺ to the SR.
D)All apply.

Question 42

The actin filament is a polymer formed from 300 to 400 globular subunits called

A)I-actin.
B)T-actin.
C)G-actin.
D)C-actin.

Question 43

The process by which action potentials cause muscle contraction is

A)the sliding filament theory.
B)excitation-contraction coupling.
C)the electromechanical release mechanism.
D)Both excitation-contraction coupling and the electromechanical release mechanism.

Question 44

During skeletal muscle contraction,

A)the H band increases in size.
B)Ca²⁺ associates with tropomyosin.
C)myosin heads interact with tropomyosin.
D)thin filaments slide across thick filaments.

Question 45

The _________ complex contains three proteins designated as the I,T,and C types.

A)actin
B)myosin
C)tropomyosin
D)troponin

Question 46

The inability of muscle cells to relax due to high frequency stimulation is termed

A)treppe.
B)recruitment.
C)twitch.
D)tetanus.

Question 47

Which of the following molecules is NOT part of the thin filament?

A)actin
B)titin
C)troponin
D)tropomyosin

Question 48

What structures carry the action potentials into the interior of the muscle to cause muscle contraction?

A)T tubules
B)terminal cisternae
C)sarcoplasmic reticula
D)ryanodine receptors

Question 49

When a muscle is stimulated to contract,calcium release channels in the SR will release Ca²⁺ by

A)active transport.
B)facilitated diffusion.
C)passive diffusion.
D)exocytosis.

Question 50

Which molecule blocks the myosin head from binding to actin in a relaxed muscle?

A)tropomyosin
B)troponin
C)calcium
D)titin

Question 51

Which of the following is NOT true of the relaxation of a muscle fiber?

A)ATP is needed to fuel the calcium pumps
B)calcium release channels close
C)the action potential must continue
D)Ca²⁺ moves from the sarcoplasm to the sarcoplasmic reticula

Question 52

Ca²⁺ must bind to tropomyosin so that the myosin binding sites on actin will be accessible to the myosin.

Question 53

The Ca²⁺ required for skeletal muscle contraction

A)is released from the sarcoplasmic reticulum.
B)enters the cell due to the opening of voltage regulated Ca²⁺ channels from the T tubules.
C)is actively transported into the cell.
D)is released from mitochondria.

Question 54

Which of the following does NOT occur during the cross bridge cycle?

A)a second ATP binding causes cross bridges to release.
B)ADP is released at the end of the power stroke.
C)energized myosin heads bind troponin.
D)ATP hydrolysis allows for cross bridge formation.

Question 55

Transverse tubules contain voltage-gated calcium channels that respond to membrane depolarization and are directly coupled to the calcium release channels in the sarcoplasmic reticulum.

Question 56

________ is characterized by continued attachment of myosin heads to actin filaments due to a lack of ATP.

A)Tetanus
B)Rigor mortis
C)Flaccid paralysis
D)Treppe

Question 57

Increasing the frequency of action potentials in a somatic motor neuron will induce increased force of muscle contraction.

Question 58

The movement of the troponin-tropomyosin complex requires

A)ATP.
B)Ca²⁺.
C)acetylcholine.
D)Na⁺.

Question 59

Summation occurs in muscle cells when stimulus frequency increases to produce a greater force contraction.

Question 60

A shortening of the muscle that occurs when the tension is greater than the load is a(n)

A)concentric contraction.
B)isometric contraction.
C)eccentric contraction.
D)isokinetic contraction.

Question 61

Isotonic muscle contractions are often preceded by isometric contractions.

Question 62

ATP in muscle contraction is needed for

A)attachment of myosin cross bridges to actin.
B)release of myosin cross bridges from actin.
C)pumping of Ca²⁺ back into the sarcoplasmic reticulum.
D)All apply.

Question 63

High-energy phosphates are stored in skeletal muscle as creatine phosphate.

Question 64

When a muscle cell generates tension but does not shorten,a(n)______ contraction occurs.

A)isometric
B)isotonic
C)spastic
D)flaccid

Question 65

Skeletal muscles at rest obtain most of their energy from the aerobic respiration of

A)glucose.
B)protein.
C)fatty acids.
D)glycogen.

Question 66

Which of the following statements about muscles is FALSE?

A)During isometric contractions muscles do not generate tension.
B)The strength of contraction is directly proportional to the stimulus intensity.
C)Tendons act as part of the series-elastic component of a muscle.
D)During muscle contraction the Z disks move closer together.

Question 67

Which of the following is NOT true about the series-elastic component to contraction?

A)It absorbs some of the tension of muscle contraction.
B)It provides for elastic recoil when muscles relax.
C)It must loosen for a muscle to shorten.
D)It is provided by tendons.

Question 68

The staircase effect or _____ represents a warm up effect due to increasing intracellular calcium concentrations.

A)treppe
B)tetanus
C)incomplete tetanus
D)tonus

Question 69

_______ refer to muscle contractions that produce a shortening muscle with a constant contraction strength at a given load.

A)Treppe contractions
B)Isotonic contractions
C)Twitch contractions
D)Isometric contractions

Question 70

Insertion of ______________ in the muscle cell membrane increases cellular glucose uptake.

A)GLUT1
B)GLUT2
C)GLUT3
D)GLUT4

Question 71

Which of the following does NOT increase the strength of the muscle contraction?

A)a high number of fibers stimulated
B)increased frequency of stimulation
C)thicker muscle fiber
D)resting sarcomere length of 3.6µm

Question 72

A force-velocity curve shows the _______ relationship between the force opposing muscle contraction and the velocity of muscle shortening.

A)direct
B)inverse
C)increased
D)no

Question 73

Which of the following is true for the first 30 minutes of heavy exercise?

A)Most energy is derived from glycogen and plasma glucose.
B)The percentage of energy obtained from plasma free fatty acids exceeds that of mild exercise.
C)The percentage of energy obtain from plasma glucose is less than that of moderate exercise.
D)All apply.

Question 74

Smooth,sustained muscle contractions in vivo are due to synchronous activation of motor units.

Question 75

Blood lactate will begin to rise when exercise is performed at a rate that is

A)15% of VO_2max.
B)25% of VO_2max.
C)50% of VO_2max.
D)85% of VO_2max.

Question 76

A muscle contraction against a resistance that is greater than the force and causes muscle lengthening is a(n)

A)concentric contraction.
B)isometric contraction.
C)eccentric contraction.
D)isokinetic contraction.

Question 77

Exceeding the VO_2max will result in lactate production by the muscle.

Question 78

In regards to the relationship between resting muscle fiber length and tension generated,

A)maximal tension is generated when the thick and thin filaments slightly overlap.
B)maximal tension is generated when the thick and thin filaments do not overlap.
C)maximal tension is generated when the thick and thin filaments greatly overlap.
D)the amount of overlap is unimportant in determining maximal tension.

Question 79

For a muscle to contract,it must overcome stronger opposing forces.

Question 80

The first 1 to 2 minutes of moderate to heavy exercise relies on _____ for ATP production.

A)aerobic respiration of glucose
B)anaerobic respiration of glucose
C)aerobic respiration of fatty acids
D)anaerobic respiration of amino acids