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2023 Systems Phys > Skeletal Muscle - Questions - High Yield > Flashcards

Skeletal Muscle - Questions - High Yield Flashcards

1
Q

Muscle cells are specialized for…

A

contraction

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2
Q

What are the 3 types of muscle?

A

skeletal
cardiac
smooth

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3
Q

Why is skeletal muscle striated?

A

due to the orderly arrangement of filaments

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4
Q

What type of control does skeletal muscle have?

A

voluntary

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5
Q

Which system is skeletal muscle innervated by?

A

somatic nervous system

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6
Q

Skeletal muscle contracts ___ and fatigues ___

A

quickly
quickly

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7
Q

Skeletal muscle has ___, depending on…

A

myosin ATPase activity
fast or slow fiber type

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8
Q

Is smooth unstriated or striated?

A

unstriated

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9
Q

What type of control does smooth muscle have?

A

involuntary

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10
Q

Which system is smooth muscle innervated by?

A

autonomic nervous system

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11
Q

Where is smooth muscle found?

A

walls of tubular organs (intestines, blood vessels)

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12
Q

What is the major concern of smooth muscle?

A

movement of materials through tubular organs

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13
Q

Smooth muscle contracts ___ and fatigues ___.

A

Slowly
Slowly

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14
Q

Smooth musle has ___ myosin ATPase activity

A

very slow

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15
Q

Is cardiac muscle striated or unstriated?

A

striated

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16
Q

What kind of control does cardiac muscle have?

A

involuntary

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17
Q

Which system innervates cardiac muscle?

A

the autonomic nervous system

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18
Q

What does it mean that cardiac muscle is myogenic?

A

it contracts spontaenously

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19
Q

Cardiac muscle has ___ myosin ATPase activity and is highly ___ resistant

A

slow
fatigue

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20
Q

What is the composition of skeletal muscles?

A

long, cylindrical, multinucleated muscle cells (muscle fibers) bundled in connective tissue

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21
Q

Define: Muscle Fibers

A

long, cylindrical, multinucleated muscle cells

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22
Q

Muscle fibers are packed with…

A

myofibrils

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23
Q

Within each myofibril is…

A

a sarcomere

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24
Q

Define: Saromere

A

an ordered arrangement of thick and thin filaments

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25
Q

Thick filaments are composed mostly of…

A

myosin

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26
Q

Thin filaments are composed of

A

actin
tropomyosin
troponin

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27
Q

What are cross-bridges composed of?

A

myosin heads

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28
Q

How do cross bridges cause contraction?

A

cross-bridges project from thick filaments and bind with actin to bring about contraction

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29
Q

Define: Neurogenic

A

only contracts when externally stimulated by a nerve

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30
Q

Is skeletal muscle neurogenic or myogenic?

A

neurogenic

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31
Q

How does a skeletal muscle contract?

A

Excitation by its motor neuron brings about contractin through a series of events that results in the thin filaments sliding closer together between the thick filaments

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32
Q

Where is ACh released in skeletal muscles?

A

from the terminal of the motor neuron

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33
Q

What effect does ACh have on skeletal muscles?

A

it initiates an action potential in the muscle cell that is propagated over the entire surface of the sarcolemma

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34
Q

How does electrical activity travel deep into skeletal muscle?

A

by T tubules

35
Q

What happens when the t tubule depolarizes?

A

movement of the voltage sensor in the dihydropyridine receptors

36
Q

What is the voltage sensor in the dihydropyridine receptors mechanically linked to?

A

the opening of the ryanodine receptor Ca2+ release channels in the SR

37
Q

What effect does Ca2+ have on skeletal muscls when it is released from the SR?

A

it binds to troponin, pulling the troponin-tropomyosin complex aside, and uncovers actin’s cross-bridge binding sites

38
Q

What occurs in the muscle when actin binding sites are opened?

A

exposed actin sites bind with myosin cross bridges

39
Q

How are the myosin cross-bridges energized before binding with actin?

A

by the hydrolysis of ATP into ADP+ Pi by the myosin ATPase ite on the cross bridges

40
Q

Binding of actin and myosin at a cross bridge causes…

A

the crossbridge head to roate 45 degrees as Pi is released

41
Q

What happens when the crossbridge head rotates?

A

it produces a power stroke that pulls the thin filament inward

42
Q

How does the myosin crossbridge detach from the actin binding sites?

A

dissociation of ADP and binding of ATP after the power stroke

43
Q

How does the cycle continue after the cross-bridge detaches?

A

splitting of fresh ATP molecule by myosin energies the crossbridge again

44
Q

What occurs in the muscle if Ca2+ is still present after the contraction cycle is finished?

A

the toponin-tropomyosin complex remains pulled aside and the crossbridges go through another cycle of binding and bending, pulling the thin filament even further

45
Q

How does contraction end?

A

When excitation stops and Ca2+ has been actively returned to its storage site, the troponin-tropomyosin complex slips back into its blocking position, actin and myosin no longe bind at the cross-bbridges, and the thin filaments slide back to their resting position as relaxation takes place

46
Q

How is Ca2+ returned to its storage site?

A

via SERCA

47
Q

Define: steric inhibition

A

troponin-tropomyosin complex slips back into its blocking position

48
Q

Define: Motor unit

A

a single α motor neuron and all of the skeletal muscles it innervates

49
Q

How does skeletal muscle generate force during contraction?

A

by shortening, lengthening or allowing the length to remain unchanged

50
Q

Define: Isotonic Contraction

A

the muscle shortens or lengthens while generating a constant amount of force

51
Q

Define: Isometric Contraction

A

the muscle generates force at a constant length

52
Q

T or F: most contractions are part isometric and part isotonic

A

TRUE

53
Q

Define: Sliding filament mechanism

A

the relationship between the length of the muscle and the tension it can develop

54
Q

Define: Optimal Length

A

active force generated is maximal

55
Q

Where is the optimal length in muscle?

A

where overlap between thick and thin filaments is maximal

56
Q

When does active tension decline?

A

at lengths both shorter and longer than optimal length

57
Q

Why does active tension decline?

A

because fewer crossbridges form

58
Q

How does the muscle obtain the ATP needed for contraction?

A
  1. immediate in the form of high energy phosphates from stored creatine phosphate
  2. non-oxidative pathways such as glycogenolysis and glycolysis which synthesize ATP w/o O2 and uses glycogen stores and generates lactic acid
  3. oxidative phosphorylation, which efficiently extracts large amounts of ATP from nutrient molecules but requires suffiecent O2
59
Q

Define: Immediate ATP pathway for contraction

A

high energy phosphates from stored creatine phosphate

60
Q

Define: Non-oxidative pathways muscles obtain ATP for contraction

A

synthesize ATP w/o O2 and uses glycogen stores and generates lactic acid
ex: glycogenolysis and glycolysis

61
Q

Define: Oxidative phosphorylation pathway muscles use to obtain ATP for contraction

A

efficiently extracts large amounts of ATP from nutrient molecules but requires suffiecent O2

62
Q

What are the 3 major skeletal muscle fiber types?

A

1 slow twitch and 2 fast twitch

63
Q

What is the difference between the 2 fast twitch muscle fibers?

A

they rely on different metabolic pathways for ATP synthesis

64
Q

Gradation of whole muscle contractioncan be accomplished by…

A
  1. varying the. number of muscle fibers contracting within the muscle
  2. varying the tension developed by each contracting fiber
65
Q

The number of muscle fibers contracting depends on….

A
  1. the size of the muscle (number of muscle fibers present)
  2. the extent of motor unit recruitment (how many motor neurons supplying the muscles are active)
  3. the size of each motor unit (how many muscle fibers are activated simultaneously by a single motor neuron)
66
Q

How is the size of a motor unit defined?

A

how many muscle fibers are activated simultaneously by a single motor neuron

67
Q

How is the ectent of motor unit recruiment determined?

A

by how many motor neurons suppllying the muscles are active

68
Q

How is the size of the muscle determined?

A

by the number of muscle fibers present

69
Q

The greater tthe tension developed by each contracting fiber….

A

the stronger the contraction of the whole muscle

70
Q

What are the two readibly variable factors relating to contraction tension?

A
  1. the frequency of stimulation
  2. the length of the fiber before onset of contraction
71
Q

What does the frequency of stimulation of a muscle contraction determine?

A

the extent of twitch summation

72
Q

Which of the following is the light band of the sarcomere?
A. A Band
B. H Zone
C. I Band
D. Z Line

A

I Band

73
Q

Which of the following remains the same width during contraction?
A. A Band
B. H Zone
C. I Band

A

A Band

74
Q

Which of the following describes a sarcomere?
A. 1 whole A Band and 1/2 of each I Band located on either side
B. 1 Z line to the next Z Line
C. The functional unit of skeletal muscle
D. All of the above

A

All of the above

75
Q

What is responsible for removing the steric inhibition for the act of contraction?

A

Ca2+

76
Q

What is responsible for detachment?

A

ATP

77
Q

All of the following result in muscle relaxation except:
A. reuptake of Ca2+ by the SR
B. No more ATP
C. no more AP
D. Removal of ACh at the end plate by AChase
E. Filaments sliding back to their restign position

A

B. No more ATP

78
Q

What is the purpose of immediate and nonoxidative pathways?

A

power -? ATP/min

79
Q

Immediate and nonoxidative energy sources activate ___ and produce energy at a ___ rate

A

Rapidly
high

80
Q

Oxidative energy sources activate __ and produce energy at a __ rate.

A

Slowly
Low

81
Q

Which fiber type makes up approximately 50% of fibers in the average muscle?

A

Type 1/Slow Twitch

82
Q

Which muscle is type 1 in everyone?

A

Soleus muscle

83
Q

Which fiber type makes up approximtely 25% of fibers in the average muscle?

A

Fast Twitch
Type IIa
Type IIx

84
Q

Which of the following is true about muscle fiber types?
A. the amount of fiber type varies from person to person
B. genetics can indicate fiber types
C. fiber types cannot be changed
D. all of the above

A

All of the above

2023 Systems Phys (41 decks)

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