Deck 12: Muscle: Mechanisms of Contraction and Neural Control

Question 1

Z discs are found bisecting the A bands.

Answer 1

False

Question 2

The more movable bony attachment is the

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

Answer 2

D

Question 3

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

Answer 3

True

Question 4

The light band of a skeletal muscle is known as the

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

Question 5

A muscle that constricts an opening is a/an

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

Question 6

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 7

When skeletal muscle cells contract,they increase in length.

Question 8

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.

Question 9

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

Question 10

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

Question 11

The prime mover of any skeletal movement is called the

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

Question 12

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

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

Question 13

Each fascicle of a muscle is surrounded by the

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

Question 14

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

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

Question 15

The epimysium surrounds the individual muscle cells.

Question 16

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

Question 17

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 18

Motor unit recruitment allows for _________ contraction strength.

A)increased
B)decreased
C)no change in

Question 19

Flexors increase the angle at a joint.

Question 20

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

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

Question 21

Thin filaments are composed of myosin and tropomyosin.

Question 22

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

Question 23

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 24

During skeletal muscle contraction the A band decreases in size.

Question 25

What protein primarily makes up the thick filament?

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

Question 26

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

Question 27

Myosin contains binding sites for ______________ and _____________.

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

Question 28

What enzyme is needed to start the cross bridging process?

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

Question 29

The thick filament is split by a Z disc.

Question 30

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

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

Question 31

What protein primarily makes up the thin filament?

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

Question 32

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

Question 33

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 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

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

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

Question 36

The thick filament is also called the

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

Question 37

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 38

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 39

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

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

Question 40

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

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

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

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 43

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 44

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 45

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

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

Question 46

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

Question 47

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

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

Question 48

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 49

The movement of the troponin-tropomyosin complex requires

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

Question 50

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

Question 51

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 52

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 53

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 54

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 55

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 56

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

Question 57

________ 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 58

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 59

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

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

Question 60

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

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

Question 61

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 62

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

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

Question 63

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 64

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 65

Isotonic muscle contractions are often preceded by isometric contractions.

Question 66

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 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

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 69

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

Question 70

_______ 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 71

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 72

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 73

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

Question 74

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 75

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 76

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 77

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

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

Question 78

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

Question 79

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

Question 80

An increase in plasma creatine phosphokinase could indicate

A)muscular dystrophy.
B)liver disease.
C)heart attack.
D)Both muscular dystrophy and heart attack.