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Chapter 9 Muscles and Muscle Tissue > Muscles and Muscles Tissue Part B > Flashcards

Muscles and Muscles Tissue Part B Flashcards

1
Q

Whole Muscle Contraction

A

Same principles apply to contraction of both single fibers and whole muscles

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2
Q

muscle tension

A

Contraction produces muscle tension, the force exerted on load or object to be moved

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3
Q

Contraction may

A

may/ may not shorten muscle

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4
Q

Isometric contraction

A

no shortening; muscle tension increases but does not exceed load numbers

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5
Q

Isotonic contraction

A

muscle shortens because muscle tension exceeds load

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6
Q

Force and duration of contraction

A

contraction vary in response to stimuli of different frequencies and intensities.

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7
Q

Each muscle is served

A

by at least one motor nerve

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8
Q

Motor nerve contains

A

axons of up to hundreds of motor neurons

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9
Q

Axons branch

A

into terminals, each of which forms NMJ with single muscle fiber

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10
Q

Motor unit define

A

is the nerve-muscle functional unit

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11
Q

Motor unit

A

unit consists of the motor neuron and all muscle fibers (four to several hundred) it supplies
Smaller the fiber number, the greater the fine control

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12
Q

The smaller fiber number is

A

the greater the fine control

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13
Q

Muscle fibers from a motor unit

A

are spread throughout the whole muscle, so stimulation of a single motor unit causes only weak contraction of entire muscle

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14
Q

Muscle twitch

A

simplest contraction resulting from a muscle fiber’s response to a single action potential from motor neuron

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15
Q

In muscles twitch the muscles fiber

A

Muscle fiber contracts quickly, then relaxes

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16
Q

Myogram

A

is when twitch can be observed and recorded

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17
Q

Tracing

A

line recording contraction activity

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18
Q

Three phases of muscle twitch

A

Latent period
Period of contraction
Period of relaxation

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19
Q

Latent period

A

events of excitation-contraction coupling.

No muscle tension seen

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20
Q

Period of contraction

A

cross bridge formation

Tension increases

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21
Q

Period of relaxation

A

Ca2+ reentry into SR

Tension declines to zero

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22
Q

Muscle contracts

A

faster than it relaxes

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23
Q

Differences in strength and duration of twitches causes

A

are due to variations in metabolic properties and enzymes between muscles.

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24
Q

Example twitches

A

eye muscles contraction are rapid and brief, whereas larger, fleshy muscles (calf muscles) contract more slowly and hold it longer

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25
Q

Normal muscle contraction

A

is relatively smooth, and strength varies with needs

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26
Q

A muscle twitch is seen

A

only in lab setting or with neuromuscular problems, but not in normal muscle

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27
Q

Graded muscle responses

A

vary strength of contraction for different demands

Required for proper control of skeletal movement

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28
Q

Responses are graded by:

A

Changing frequency of stimulation

Changing strength of stimulation

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29
Q

Muscle response

A

to changes in stimulus frequency

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30
Q

Single stimulus

A

results in single contractile response (i.e., muscle twitch)

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31
Q

Wave Temporal summation

A

results if two stimuli are received by a muscle in rapid succession.

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32
Q

Muscle fibers do not have time

A

completely relax between stimuli, so twitches increase in force with each stimulus

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33
Q

Additional Ca2+ that

A

is released with second stimulus stimulates more shortening

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34
Q

If stimuli frequency increases

A

muscle tension reaches near maximum

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35
Q

Produces smooth

A

continuous contractions that add up (summation)

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36
Q

Further increase in stimulus frequency

A

frequency causes muscle to progress to sustained, quivering contraction referred to as unfused (incomplete) tetanus

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37
Q

fused (complete) tetanus

A

because contractions “fuse” into one smooth sustained contraction plateau

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38
Q

Prolonged muscle contractions

A

lead to muscle fatigue

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39
Q

Recruitment (or multiple motor unit summation):

A

stimulus is sent to more muscle fibers, leading to more precise control

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40
Q

Types of stimulus involved in recruitment:

A

Subthreshold stimulus
Threshold stimulus
Maximal stimulus

41
Q

Subthreshold stimulus

A

stimulus not strong enough, so no contractions seen

42
Q

Threshold stimulus

A

stimulus is strong enough to cause first observable contraction

43
Q

Maximal stimulus

A

strongest stimulus that increases maximum contractile force

44
Q

All motor unit

A

have been recruited

45
Q

Recruitment works

A

on size principle

46
Q

Motor units with smallest

A

muscle fibers are recruited first

47
Q

Motor units with larger

A

larger fibers are recruited as stimulus intensity increases

48
Q

Largest motor units

A

activated only for most powerful contractions

49
Q

Motor units in muscle

A

usually contract asynchronously

50
Q

Some fibers contract

A

while others rest,

Helps prevent fatigue

51
Q

Muscle Tone

A

Constant, slightly contracted state of all muscles. Due to spinal reflexes

52
Q

Groups of motor units

A

alternately activated in response to input from stretch receptors in muscles

53
Q

Muscle Tone

A

Keeps muscles firm healthy, and ready to respond

54
Q

Isotonic contractions

A

muscle changes in length and moves load.

Isotonic contractions can be either concentric or eccentric:

55
Q

Concentric contractions and examples

A

muscle shortens and does work

Example: biceps contract to pick up a book

56
Q

Eccentric contractions and examples

A

muscle lengthens and generates force.

Example: laying a book down causes biceps to lengthen while generating a force

57
Q

Isometric contractions

A

Load is greater than the maximum tension muscle can generate, so muscle neither shortens nor lengthens

58
Q

Electrochemical and mechanical events

A

same in isotonic or isometric contractions, but results are different

59
Q

In isotonic contractions

A

actin filaments shorten and cause movement

60
Q

In isometric contractions

A

cross bridges generate force, but actin filaments do not shorten.

61
Q

Myosin heads

A

“spin their wheels” on same actin- binding site

62
Q

ATP supplies the energy needed for the muscle fiber

first to:

A

Move and detach cross bridges

63
Q

ATP supplies the energy needed for the muscle fiber second to:

A

Pump calcium back into SR

64
Q

ATP supplies the energy needed for the muscle fiber third to:

A

Pump Na+ out of and K+ back into cell after excitation-contraction coupling

65
Q

Available stores of ATP

A

depleted in 4–6 seconds

66
Q

ATP is the only source of energy

A

for contractile activities; therefore it must be regenerated quickly

67
Q

ATP is regenerated quickly by three mechanisms:

A

Direct phosphorylation of ADP by creatine phosphate (CP)
Anaerobic pathway: glycolysis and lactic acid formation
Aerobic pathway

68
Q

Creatine phosphate

A

is a unique molecule located in muscle fibers that donates a phosphate to ADP to instantly form ATP

69
Q

Creatine kinase

A

kinase is enzyme that carries out transfer of phosphate

70
Q

Muscle fibers have enough ATP

A

and CP reserves to power cell for about 15 seconds

71
Q

Muscle fibers have enough ATP

A

CP reserves to power cell for about 15 seconds

72
Q

Creatine phosphate + ADP →

A

creatine + ATP

73
Q

ATP can also be generated

A

by breaking down and using energy stored in glucose

74
Q

Glycolysis

A

first step in glucose breakdown.

Does not require oxygen.

Glucose is broken into 2 pyruvic acid molecules.

2 ATPs are generated for each glucose broken down

75
Q

Low oxygen levels prevent pyruvic acid

A

from entering aerobic respiration phase

76
Q

Normally, pyruvic acid enters

A

mitochondria to start aerobic respiration phase; however, at high intensity activity, oxygen is not available

77
Q

Bulging muscles compress

A

blood vessels, impairing oxygen delivery

78
Q

In the absence of oxygen

A

referred to as anaerobic glycolysis, pyruvic acid is converted to lactic acid.

79
Q

Lactic acid

A

Diffuses into bloodstream.

Used as fuel by liver, kidneys, and heart.

Converted back into pyruvic acid or glucose by liver

80
Q

Anaerobic respiration yields only

A

5% as much ATP as aerobic respiration, but produces ATP 2½ times faster

81
Q

Aerobic Respiration

A

Produces 95% of ATP during rest and light-to-moderate exercise.
Slower than anaerobic pathway

82
Q

Aerobic Respiration consist of

A

of series of chemical reactions that occur in mitochondria and require oxygen

83
Q

Aerobic Respiration breaks

A

glucose into CO2, H2O, and large amount ATP (32 can be produced)

84
Q

Fuels used include (Aerobic Respiration)

A

glucose from glycogen stored in muscle fiber, then bloodborne glucose, and free fatty acids.

85
Q

Fatty acids(Aerobic Respiration)

A

are main fuel after 30 minutes of exercise

86
Q

Energy systems used during sports

A

Aerobic endurance

Anaerobic threshold

87
Q

Aerobic endurance

A

Length of time muscle contracts using aerobic pathways

Light-to-moderate activity, which can continue for hours

88
Q

Anaerobic threshold

A

Point at which muscle metabolism converts to anaerobic pathway

89
Q

Muscle Fatigue

A

Fatigue is the physiological inability to contract despite continued stimulation

90
Q

Possible causes of muscles fatigue include:

A

Ionic imbalances can cause fatigue

Levels of K+, Na+ and Ca2+ can change disrupting membrane potential of muscle cell

91
Q

Increased inorganic phosphage

A

(Pi) from CP and ATP breakdown may interfere with calcium release from SR or hamper power

92
Q

Decreased ATP and increases magnesium.

A

As ATP levels drop magnesium levels increase and this can interfere with voltage sensitive T tubule proteins

93
Q

glycogen

A

decreases in muscles fatigue

94
Q

Lack of ATP

A

rarely a reason for fatigue, except in severely stressed muscles

95
Q

Excess Postexercise Oxygen Consumption

A

All replenishing steps require extra oxygen.

Formerly referred to as “oxygen debt”

96
Q

muscles pre-exercise state:

A

Oxygen reserves are replenished.

97
Q

muscles pre-exercise state:

A

Lactic acid is reconverted to pyruvic acid

98
Q

muscles pre-exercise state:

A

Glycogen stores are replaced

99
Q

muscles pre-exercise state:

A

ATP and creatine phosphate reserves are resynthesized

Chapter 9 Muscles and Muscle Tissue (5 decks)

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