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Human Phys LFS112 > Week 3, Muscle > Flashcards

Week 3, Muscle Flashcards

1
Q

Identify the incorrect statement about a single motor unit.
Answers:

The more neurons involved, the more powerful the contraction.

The smaller the number of muscle fibers, the more precise the movement.

Fine motor skills depend on the development of small motor units.

Some motor units include as many as 2000 muscle fibers.

Muscle fibers of one motor unit intermingle with the fibers of another motor unit.

A

The more neurons involved, the more powerful the contraction.

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2
Q

The increase in muscle tension that is produced by increasing the number of active motor units is called

A

recruitment.

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3
Q

Each skeletal muscle fiber contains ________ myofibrils.

A

hundreds to thousands

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4
Q

In a sarcomere, the central portion of thick filaments are linked laterally by proteins of the

A

M line.

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5
Q

Deep inward extensions of the sarcolemma form a tunnel-like network inside the muscle cell known as;

A

transverse tubules (T-tubules).

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6
Q

When a skeletal muscle fiber contracts, the

A

zones of overlap get larger.

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7
Q

Nerves and blood vessels that service a muscle fiber are located in the connective tissues of its

A

endomysium.

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8
Q

The skeletal muscle complex known as the triad consists of

A

a transverse tubule and two terminal cisternae.

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9
Q

A single motor neuron together with all the muscle fibers it innervates is called a(n)

A

motor unit.

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10
Q

The action potential is conducted into a skeletal muscle fiber by

A

transverse tubules.

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11
Q

The type of contraction in which the muscle fibers do not shorten is called

A

isometric.

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12
Q

At each end of the muscle, the collagen fibers of the epimysium, perimysium, and endomysium, come together to form a

A

tendon.

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13
Q

Active sites on the actin become available for binding after

A

calcium binds to troponin.

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14
Q

Which of the following best describes the term sarcomere?
Answers:
protein that accounts for elasticity of resting muscle

repeating unit of striated myofibrils

storage site for calcium ions

thin filaments are anchored here

largely made of myosin molecules

A

repeating unit of striated myofibrils

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15
Q

The region of the sarcomere that always contains thin filaments is the

A

I band.

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16
Q

Which of the following best describes the series of membranous channels that surround each myofibril called the sarcoplasmic reticulum?
Answers:
protein that accounts for elasticity of resting muscle

repeating unit of striated myofibrils

storage and release site for calcium ions

thin filaments are anchored here

largely made of myosin molecules

A

storage and release site for calcium ions

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17
Q

The following is a list of the events that occur during a muscle contraction. What is the correct sequence of these events?

  1. Myosin cross-bridges bind to the actin.
  2. The free myosin head splits ATP.
  3. Calcium ion is released from the sarcoplasmic reticulum.
  4. The myosin head pivots toward the center of the sarcomere.
  5. Calcium ion binds to troponin.
  6. The myosin head binds an ATP molecule and detaches from the actin.

Answers:
1, 3, 5, 4, 6, 2

5, 1, 4, 6, 2, 3

3, 5, 1, 2, 4, 6

3, 5, 1, 4, 6, 2

1, 4, 6, 2, 3, 5

A

3, 5, 1, 4, 6, 2

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18
Q

Skeletal muscle fibers are formed from embryonic cells called

A

myoblasts

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19
Q

The most important factor in decreasing the intracellular concentration of calcium ion after contraction is

A

active transport of calcium into the sarcoplasmic reticulum.

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20
Q

How would the loss of acetylcholinesterase from the motor end plate affect skeletal muscle?

A

It would cause muscles to stay contracted.

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21
Q

What is required for excitation-contraction coupling in skeletal muscle?

A

calcium ions and ATP.

22
Q

The neurotransmitter which binds to the receptors on the motor end plate is;

A

acetylcholine.

23
Q

The type of muscle fiber that is most resistant to fatigue is the ________ fiber.

A

slow

24
Q

Which of the following best describes the term titin?

A

protein that accounts for elasticity of resting muscle

25
Q

The area in the center of the A band that contains no thin filaments is the

A

H band.

26
Q

The region of the sarcomere that always contains thin filaments is the

A

I band.

27
Q

When calcium ion binds to troponin,

A

tropomyosin rolls away from the active site.

28
Q

When a muscle is stimulated repeatedly at a high rate, the amount of tension gradually increases to a steady maximum tension. This state of maximum tension is called

A

complete tetanus.

29
Q

Which of the following is a recognized function of skeletal muscle?
Answers:
produce movement

maintain posture

maintain body temperature

guard body entrances and exits

All of the answers are correct.

A

All of the answers are correct.

30
Q

Interactions between actin and myosin filaments of the sarcomere are responsible for

A

muscle contraction.

31
Q

Triggering of the muscle action potential occurs after

A

acetylcholine binds to chemically-gated channels in the motor end plate

32
Q

A single contraction-relaxation cycle in a muscle fiber produces a(n)

A

twitch.

33
Q

The structural theory that explains how a muscle fiber contracts is called the ________ theory.

A

sliding filament

34
Q

Which of the following acts as an ATPase during the contraction cycle of muscle?

A

the head portion of the myosin molecule

35
Q

Where are most of the calcium ions (Ca2+) located when a muscle cell is at rest?

A

sarcoplasmic reticulum.

36
Q

The plasma membrane of a skeletal muscle fiber is called the

A

sarcolemma.

37
Q

You try to pick up an object and discover that it is much heavier than you expected. Which process must occur in the muscle to increase tension so you can pick up the object?

A

recruitment

38
Q

Cross bridge detachment is caused by ________ binding to the myosin head.

A

ATP

39
Q

Which of the following types of muscle fibers are best adapted for prolonged contraction such as standing all day?

A

slow fibers

40
Q

Muscular force can be adjusted to match different loads by
Answers:
varying the frequency of action potentials in motor neurons.

recruiting larger motor units.

recruiting more motor units.

involving more muscle fibers in the contraction.

All of the answers are correct.

A

All of the answers are correct.

41
Q

The dense layer of connective tissue that surrounds an entire skeletal muscle is the

A

epimysium.

42
Q

In an isotonic contraction,

A

muscle tension exceeds the load and the muscle lifts the load.

43
Q 
Put the following structures in order from superficial to deep.
1.    muscle fiber        
2.    perimysium        
3.    myofibril            
4.    fascicle
5.    endomysium
6.    epimysium 
Answers: 
1, 5, 4, 3, 2, 6

6, 2, 5, 4, 1, 3

6, 2, 4, 5, 1, 3

1, 3, 5, 6, 4, 2

2, 3, 1, 4, 6, 5

A

6, 2, 4, 5, 1, 3

44
Q

At rest, active sites on actin are blocked by

A

tropomyosin molecules.

45
Q

Cross-bridges are portions of

A

myosin molecules.

46
Q

A muscle producing almost peak tension during rapid cycles of contraction and relaxation is said to be in

A

incomplete tetanus.

47
Q

Which of the following statements is/are false regarding human muscles?

A

Slow fibers are abundant in the muscles of the hand

48
Q

Fast fibers

A

have low resistance to fatigue and quick twitches.

49
Q

The sequence of processes that links the action potential to contraction is called

A

excitation-contraction coupling.

50
Q

Each skeletal muscle fiber is controlled by a motor neuron at a single

A

neuromuscular junction.

Human Phys LFS112 (12 decks)

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