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A&P Exam 2 > Chapter 10 - Muscle Tissue - PART 3 > Flashcards

Chapter 10 - Muscle Tissue - PART 3 Flashcards

1
Q

When sarcomeres shorten in a contraction, they shorten the ______

A

muscle fiber

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2
Q

What produces tension on the connective tissue fibers attached to the muscle fiber?

A

the shortening of the muscle fiber (due to the shortening of sarcomeres)

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3
Q

The amount of tension produced by an individual muscle fiber ultimately depends on….

A

the number of pivoting cross-bridges

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4
Q

The tension produced by an individual muscle fiber varies for which 2 reasons?

A
  1. The fiber’s resting length at the time of the stimulation (determines the degree of overlap when stimulated)
  2. The frequency of stimulation (affects internal concentration of calcium ions and thus the amount bound to troponin)
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5
Q

In a skeletal muscle fiber, the amount of tension generated during a contraction depends on……

A

the number of pivoting cross-bridges in each of the myofibrils

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6
Q

The number of cross-bridges that can form depends on…..

A

the degree of overlap between thin and thick filaments within the sarcomeres

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7
Q

When a muscle fiber is stimulated to contract, only ___ in the _____ can bind to the active sites of actin and produce ______

A

when a muscle fiber is stimulated to contract, only MYOSIN HEADS in the ZONES OF OVERLAP can bind to the active sites of actin and produce TENSION

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8
Q

A sarcomere works most efficiently within an optimal range of lengths. What determines this optimal range?

A

The MAXIMUM number of cross bridges can form and the tension produced is the highest

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9
Q

What largely determines the amount of tension produced?

A

the number of cross-bridges that form

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10
Q

An increase in sarcomere length _____ the tension. WHY?

A

An increase in sarcomere length REDUCES the tension because an increase in size reduces the zone of overlap and thus the amount of cross-bridges that can form

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11
Q

A decrease in the resting sarcomere length ______ efficiency

A

reduces

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12
Q

Why does a decrease in the resting length of a sarcomere reduce efficiency?

A

because the thin filaments will extend across the center of the sarcomere and collide with or overlap the thin filaments of the opposite side. This interferes with the binding of myosin heads to the active sites and the propagation of action potential along T tubules

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13
Q

Tension production falls to zero when……

A

the resting sarcomere is at its shortest length

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14
Q

What happens to the internal structure of a sarcomere when its at its shortest resting length?

A

the thick filaments are jammed against the Z LINES. Cross-bridge binding can still occur, but the myosin heads cannot pivot and generate tension because the thin filaments cannot move

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15
Q

What protein prevents a sarcomere from stretching so much that the zone of overlap is reduced to zero?

A

TITIN

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16
Q

titin binds ___ to ____

A

ties the thick filaments to the z lines

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17
Q

When is maximum tension produced?

A

when the zone of overlap is large but the thin filaments do not extend across the sarcomere’s center

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18
Q

A single stimulation produces a single _____ or _____

A

a single stimulation produces a single CONTRACTION, or TWITCH

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19
Q

Twitches in which muscle are the quickest? slowest?

A

quickest - eye muscle
slowest - soleus (a small calf muscle)

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20
Q

twitches are too ____ to be a part of ____ _____

A

twitches are too BRIEF to be a part of NORMAL ACTIVITY

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21
Q

a ___ shows differences in tension over time for a twitch in different skeletal muscles

A

myogram

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22
Q

A single twitch can be divided into a ____, _____, and _____

A

latent period, contraction phase, and relaxation phase

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23
Q

the latent period begins at _____

A

stimulation

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24
Q

What is happening during the latent period?

A

action potential sweeps across the sarcolemma and the sarcoplasmic reticulum releases calcium ions

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25
Q

Does the muscle fiber produce tension during the latent period? why or why not

A

NO because the contraction cycle hasn’t begun yet

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26
Q

What can you say about tension in the contraction phase?

A

tension reaches its peak in the contraction phase

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27
Q

As the tension rises in the contraction phase, what is happening to calcium ions?

A

they are binding to troponin, thus active sites on thin filaments are being exposed and cross-bridge interactions are occurring

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28
Q

What is happening in the relaxation phase?

A

calcium levels are falling, active sites are being covered by tropomyosin, and the number of active cross-bridges is declining as they detach. As a result, tension falls to resting levels

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29
Q

What is a “treppe” pattern?

A

if skeletal muscle is stimulated a second time immediately after the relaxation phase has ended, the resulting contraction will have a slightly higher max tension. The increase in max tension will continue for the first 30-50 stimulations. After that, the tension produced will remain constant. this pattern is called TREPPE

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30
Q

What is thought to be the reason for a rise in max tension if the muscle is stimulated immediately after the relaxation phase has ended?

A

likely to result from a gradual increase of calcium ions in the sarcoplasm due to the fact that the calcium ion pumps in the Sarcoplasmic Reticulum have too little time to recapture the ions between stimulations

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31
Q

do most skeletal muscles undergo treppe?

A

NO - most dont

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32
Q

What is wave summation?

A

if a second stimulus arrives BEFORE the relaxation phase has ended, a second, more powerful contraction occurs. The addition of one twitch to another in this way is called wave summation

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33
Q

What is incomplete tetanus?

A

if the stimulation continues and the muscle is never allowed to relax completely, tension will rise until it reaches a peak value roughly 4 TIMES the maximum produced by treppe

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34
Q

What is complete tetanus?

A

When an even higher stimulation frequency eliminates the relaxation phase. Action potentials arrive so rapidly that the SR does not have time to reclaim the calcium ions. The high calcium concentration in the cytoplasm prolongs the contraction, making it continuous

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35
Q

In complete tetanus, the tension _______

A

plateaus at maximal levels

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36
Q

“wave frequency” is expressed in……

A

the number of stimuli per unit time

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37
Q

The amount of tension produced by the muscle as a whole =

A

the sum of the tensions generated by the individual muscle fibers (since they are all pulling together)

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38
Q

You can control the amount of tension produced by a skeletal muscle by controlling…..

A

the number of muscle fibers stimulated (Since they all work together)

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39
Q

a typical skeletal muscle contains _____ of muscle fibers

A

thousands

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40
Q

All of the muscle fibers controlled by a SINGLE MOTOR NEURON constitutes a…….

A

motor unit

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41
Q

Where do we have more precise movement - in our eyes or leg muscles? explain

A

eye because a single motor neuron controls many less muscle fibers than a motor neuron in a leg muscle

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42
Q

When we decide to perform a voluntary movement, what is stimulated?

A

specific groups of motor neurons in the spinal cord

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43
Q

After the specific groups of motor neurons in the spinal cord are stimulated to perform a certain voluntary movement, what happens next?

A

The contraction begins with the activation of the SMALLEST motor units in the stimulated muscle. As the movement continues, larger motor units containing faster, more powerful muscle fibers are activated, and tension rises steeply.
RECRUITMENT

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44
Q

What is recruitment?

A

the smooth, but steady increase in muscular tension produced by increasing the number of active motor units

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45
Q

peak tension occurs when all motor units in the muscle contract in a state of…….

A

COMPLETE TETANUS

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46
Q

Do muscle contractions in complete tetanus last long? explain

A

NO because such powerful contractions cause the individual muscle fibers to use up all of their available energy reserves

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47
Q

what is “asynchronous motor unit summation”?

A

a “relay team” approach in which each motor unit can recover somewhat before it is stimulated again

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48
Q

When your muscles contract for sustained periods…..

A

they produce slightly less than maximal tension (because they recover)

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49
Q

some motor units are always _______ even when…..

A

some motor units are always ACTIVE even when the muscle is not CONTRACTING

50
Q

what is “muscle tone”

A

the resting tension of the motor units that are always active in the skeletal muscle, but do not produce enough tension to cause movement

51
Q

Resting muscle tone does what to bones and joints?

A

stabilizes them

52
Q

Heightened muscle tone accelerates the…..

A

recruitment process during a voluntary contraction

53
Q

The greater the muscle tone, the higher the ________

A

“resting rate” of metabolism

54
Q

“The greater the muscle tone, the higher the resting rate of metabolism”
Explain—

A

all activated muscle fibers use up energy

55
Q

“the greater the muscle tone the higher the resting rate of metabolism”
-what is this useful for in every day life?

A

the effects of exercise to lose weight

56
Q

We can classify muscle contractions as ___ or ____

A

isotonic or isometric

57
Q

In an isotonic contraction….

A

tension rises and the skeletal muscle’s length changes.

58
Q

Name some movements that involve isotonic contractions

A

lifting an object, walking, running

59
Q

There are ____ types of isotonic reactions:

A

2 types of isotonic reactions: concentric and eccentric

60
Q

“muscle tension exceeds the load and the muscle shortens”
-concentric or eccentric?

A

concentric

61
Q

The speed of shortening in a concentric contraction is dependent on which 2 things?

A

the amount of tension produced and the size of the load

62
Q

if the muscle barely produces enough tension to overcome the load, will it shorten quickly or slowly?
(concentric contraction)

A

SLOWLY

63
Q

“the peak tension developed is less than the load and the muscle elongates due to the contraction of another muscle or the pull of gravity”
(concentric or eccentric contraction)

A

eccentric contraction

64
Q

Which are more common - concentric or eccentric contractions?

A

eccentric

65
Q

During physical training, to people prefer to do eccentric or concentric contractions?

A

cycles of both (flexion=concentric, extension = eccentric)

66
Q

In an isometric reaction…

A

the muscle has a whole does NOT change length and the tension produced NEVER exceeds the load

67
Q

give some examples of isometric contractions

A

carrying a bag of groceries and holding our heads up

68
Q

(concentric or isometric)
in which does the contracting muscle bulge?

A

isometric

69
Q

does the muscle shorten in an isometric reaction?

A

the muscle as a whole does not shorten but the individual muscle fibers shorten as the connective tissues stretch

70
Q

-Lifting a baby
-holding a baby at arm’s length
–determine which is isometric and which is isotonic

A

isometric = holding at arm’s length
isotonic=lifting a baby

71
Q

In an isotonic reaction—-
-muscle tension
-muscle length

determine which remains constant and which changes

A

changes: muscle length
remains constant: muscle tension

72
Q

in an isometric reaction–
-muscle tension
-muscle length

determine which remains constant and which changs

A

changes - muscle tension
remains constant - muscle length

73
Q

The LOAD and SPEED of a reaction are…..

A

inversely related. That’s why you can lift a lighter object more rapidly than a heavy one

74
Q

If the load is LESS than the tension produced, what contraction will occur?

A

concentric isotonic contraction
-muscle will shorten-

75
Q

The heavier the load, the longer it takes for the movement to begin. WHY?

A

Because muscle tension increases gradually and it must exceed the load before shortening can occur

76
Q

At the molecular level, the speed of _____ is reduced as the load increases

A

cross-bridge pivoting

77
Q

Will the muscle shorten less the heavier the load?

A

YES

78
Q

For each muscle, an optimal combination of ___ and ___ exists for any given load

A

speed and tension

79
Q

Is there an active mechanism for muscle fiber elongation?

A

no

80
Q

Since there is no active mechanism for muscle fiber elongation after a contraction, how does a muscle return to its original size?

A

through a combination of elastic forces and opposing muscle contractions, and gravity

81
Q

Which returns a muscle back to its original length quicker - elastic forces or opposing muscle contractions?

A

opposing muscle contractions

82
Q

Gravity may assist WHAT in quickly returning a muscle to its resting length?

A

opposing muscle groups

83
Q

Why does a muscle that has been overstretched produce less tension?

A

A muscle’s ability to contract depends on the formation of cross-bridges between the actin and myosin myofilaments. In a muscle that is overstretched, the myofilaments would overlap very little, so very few cross bridges could form, and thus contraction would be weak. if the myofilaments did not overlap at all, then no cross bridges could form and the muscle could not contract

84
Q

Can a skeletal muscle contract without shortening?

A

YES
shorten = isotonic, concentric

elongate = isotonic, eccentric

remain the same length = isometric

-all depends on the relationship between the load and the tension produced by actin-myosin interactions

85
Q

ATP demands of a contracting skeletal muscle are….

A

enormous

85
Q

ATP demands of a contracting skeletal muscle are….

A

enormous

86
Q

The primary function of ATP is to….

A

transfer energy from one location to another rather than to store it long term

87
Q

At rest, a skeletal muscle fiber produces….

A

more ATP than it needs

88
Q

Under the conditions where a resting skeletal muscle fiber produces more ATP than it needs, ATP transfers energy to _____

A

creatine

89
Q

What is creatine?

A

a small molecule that muscle cells assemble from fragments of amino acids

90
Q

The energy transfer from ATP to creatine creates….

A

another high energy molecule called creatine phosphate (CP)

91
Q

During a contraction, each myosin head….

A

breaks down ATP producing ADP and Pi.

92
Q

The energy stored in creatine phosphate is used to…….

A

“recharge” ADP after it is produced by the breakdown of ATP my myosin. Converts ADP back to ATP

93
Q

What is the enzyme that facilitates the reaction of creatine phosphate converting ADP back to ATP?

A

Creatine Kinase

94
Q

A high blood concentration of creatine kinase usually indicates….

A

serious muscle damage

95
Q

Why does a high blood concentration of creatine kinase indicate serious muscle damage?

A

because when muscle cells are damaged creatine kinase leaks across the plasma membranes and into the bloodstresm

96
Q

Does a resting skeletal muscle fiber contain more creatine phosphate or ATP?

A

creatine phosphate

97
Q

For each molecule of pyruvate “fed” into the citric acid cycle, how many ATP molecules are produced?

A

17

98
Q

In a resting skeletal muscle, the demand for ATP is ____

A

low

99
Q

An active skeletal muscle is said to be fatigued when…..

A

it can no longer perform the required level of activity

100
Q

Fatigue has been linked to damage of…

A

the sarcolemma and sarcoplasmic reticulum

101
Q

Explain the type of fatigue that affects endurance trainers such as marathon runners

A

fatigue that occurs due to depletion of glycogen, lipid, and amino acid reserves

102
Q

Describe the fatigue experienced by sprinters

A

when a muscle produces a sudden, intense burst of activity at peak levels, glycolysis produces most of the ATP. After just seconds to minutes, the lactic acid levels lower the tissue pH and the muscle can no longer function normally

103
Q

Normal muscle function requires which 4 things?

A
  1. Substantial intracellular reserves
  2. A normal circulatory supply
  3. Normal blood oxygen levels
  4. Blood pH within normal limits
104
Q

Anything that interferes with the 4 requirements for normal muscle function will….

A

cause premature fatigue

105
Q

When a muscle fiber contracts, how do conditions in the sarcoplasm change?

A

energy reserves are consumed, heat is released, and if the contractions were at peak levels, lactic acid is generated.

106
Q

What happens during the recovery period?

A

the conditions in muscle fibers are returned to normal, pre-exertion levels

107
Q

what process enables skeletal muscles to continue contracting even when mitochondrial activity is limited by the availability of oxygen?

A

glycolysis

108
Q

Why is lactic acid production (glycolysis) not an efficient way of producing ATP?

A

it squanders the glucose reserves and is potentially dangerous because lactic acid dissociation can lower the pH of the blood and tissues

109
Q

During the recovery period (when oxygen is in abundance), lactate can be converted back to……

A

pyruvate

110
Q

What organ absorbs the lactate and converts it to pyruvate?

A

the liver

111
Q

The ATP produced in the citric acid cycle is used to….

A

roughly 30% are used to convert pyruvate back to glucose and is transported to muscle cells to rebuild their glycogen reserves

112
Q

The shuffling of lactate to the liver and glucose back to muscle cells is called…..

A

the Cori cycle

113
Q

During the recovery period, what can you say about the body’s oxygen demand?

A

demand remains elevated above normal resting levels

114
Q

The amount of oxygen required to restore normal, pre-exertion conditions is called the….

A

oxygen debt

115
Q

Why do we breathe heavily long after we stop exercising?

A

the oxygen debt is being repaid

116
Q

What hormones of the endocrine system adjust metabolic activities in skeletal muscle fibers?

A

Growth hormone and testosterone
thyroid hormone and epinephrine

117
Q

How do muscle cells continuously synthesize ATP?

A

By utilizing creatine phosphate and metabolizing glycogen and fats. Most cells generate ATP through aerobic metabolism in the mitochondria and through glycolysis in the cytoplasm

118
Q

What is muscle fatigue?

A

a muscle’s reduced ability to contract due to low pH (lactic acid buildup and dissociation), low ATP levels, or other problems

119
Q

Define oxygen debt

A

the amount of oxygen required to restore normal, pre-exertion conditions in muscle tissue

A&P Exam 2 (19 decks)

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