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BIOL 223 Lecture > CH 9 - Muscle Tissue & Physiology > Flashcards

CH 9 - Muscle Tissue & Physiology Flashcards

1
Q

Intercalated disc

A

Specialized junctions only found in cardiac muscle

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2
Q

Sphincter

A

A ring of muscle tissue that encircles an opening

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3
Q

What are the 6 functions of muscle tissue?

A

Produce body movement

Maintain body posture/position

Support soft tissue

Guard entrances and exits

Maintain body temperature

Store nutrient reserves

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4
Q

Excitability (irritability)

A

Ability to receive and respond to an internal or external stimulus

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5
Q

Contractility

A

Ability to shorten forcibly when adequately stimulated

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6
Q

Extensibility

A

Ability to be stretched or extended

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7
Q

Elasticity

A

Ability to recoil and resume its resting length after being stretched

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8
Q

What is the epimysium made of? What is its function?

A

Dense collagenous CT

Separates muscle from surrounding tissues and organs

Connects or blends into the muscle fascia

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9
Q

What is the perimysium made of? What are its functions?

A

Dense collagenous CT, blood vessels, nerves

Surrounds fascicles

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10
Q

Fascicle

A

A bundle of muscle fibers bound by a perimysium

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11
Q

What is the endomysium made of? What are its functions?

A

Elastic and reticular CT, capillary networks, satellite cells, nerve fibers

Surrounds each muscle fiber

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12
Q

Satellite cells

A

Muscular stem cells made from lingering myoblasts that aid in skeletal muscle replacement

*Skeletal muscle cannot regenerate

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13
Q

How are muscles attached to bones?

A

The muscle fascia is continuous with the tendon attached to the bone’s periosteum

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14
Q

Muscle fascia

A

A band (tendon) or sheet (aponeurosis) of CT that extends beyond the muscle for attachment to bone

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15
Q

Origin

A

Attachment of a muscle on a stationary bone

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16
Q

Insertion

A

Attachment of a muscle on a bone that moves

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17
Q

Agonist (prime mover)

A

The primary muscle that enables the movement by shortening

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18
Q

Antagonist

A

The primary muscle that opposes the movement by lengthening

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19
Q

Synergistic muscle

A

A muscle that prevents unwanted movements and aids the movement of the agonist

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20
Q

How are skeletal muscles formed?

A
  1. Embryonic mesoderm cells called myoblasts undergo cell division
  2. Several myoblasts fuse to form a myotube
  3. Myotube matures into a skeletal muscle fiber
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21
Q

Sarcolemma

A

The plasma membrane of the muscle fiber

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22
Q

Sarcoplasm

A

The cytoplasm of the muscle fiber

*Contains glycosomes and myoglobin

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23
Q

Transverse (T) tubule

A

The part of the sarcolemma that penetrates into the sarcoplasm of the muscle fiber to conduct and transmit the muscle action potential

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24
Q

Myofibril

A

Rodlike structures densely packed into the muscle fiber that are responsible for skeletal muscle contraction

*Contains myofilaments

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25
Q

What is the thick myofilament?

A

Myosin

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26
Q

What are the thin myofilaments?

A

Actin
Troponin
Tropomyosin
Nebulin

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27
Q

What is the elastic myofilament?

A

Titin

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28
Q

Sarcoplasmic reticulum

A

Smooth endoplasmic reticulum and site of calcium ion storage that encircles each myofibril

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29
Q

Triad

A

A T tubule and both of the terminal cisternae of the sarcoplasmic reticulum

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30
Q

Terminal cisternae

A

The portion of the sarcoplasmic reticulum in direct contact with the T tubule

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31
Q

Sarcomere

A

The smallest contractile unit measured between two Z-discs

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32
Q

A band

A

The length of the thick myofilaments that remains constant regardless of muscle contraction

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33
Q

I band

A

The distance between thick myofilaments that shortens during muscle contraction

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34
Q

H zone

A

The distance between thin myofilaments that shortens during muscle contraction

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35
Q

Myomesin

A

A structural protein that forms the M line

Also binds to titin and connects adjacent thick myofilaments together

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36
Q

Dystrophin

A

A structural protein that links thin myofilaments to membrane proteins in the sarcolemma

Helps reinforce the sarcolemma

Helps transmit tension generated by sarcomeres to tendons

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37
Q

a-Actinin

A

A structural protein of the Z disc that attaches to actin and titin

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38
Q

Filamentous actin (F-actin)

A

A thin myofilament protein

Two twisted rows of globular actin (G-actin) with each G-actin containing a myosin binding site

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39
Q

Nebulin

A

A thin myofilament protein

A long, nonelastic protein that holds F-actin together and anchors thin myofilaments to the Z disc

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40
Q

Tropomyosin

A

A thin myofilament protein

A double stranded protein molecule that spirals around actin core and helps stiffen the F-actin

Covers the myosin binding site on actin

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41
Q

Troponin

A

A thin myofilament protein

Globular protein composed of three subunits that binds tropomyosin to G-actin

Controlled by calcium ions

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42
Q

What makes up the troponin complex?

A

TnT - binds to tropomyosin
TnC - binds to calcium
TnI - binds to actin

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43
Q

How does calcium expose the myosin binding site of actin?

A

Calcium ions bind to TnC, causing a structural change that moves the entire troponin complex aside, exposing the myosin binding site.

*Stays this way until calcium is removed

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44
Q

What are the two binding sites on a myosin head?

A

ATP binding site

Actin binding site

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45
Q

What is the relaxed form of myosin called? Is it high or low energy?

A

Cocked

High energy

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46
Q

What is the pivoted form of myosin called? Is it high or low energy?

A

Power stroke

Low energy

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47
Q

Cross-bridges

A

Myosin heads interact with myosin binding site on G-actin

48
Q

Sliding filament mechanism

A

Thin myofilaments of the sarcomere slide towards the M line

A band width is unchanged

H zone, I band disappear

Z discs move closer together

49
Q

Neuromuscular junction

A

A specialized intercellular connection between a somatic motor neuron and and a skeletal muscle fiber

50
Q

Synaptic knob (synaptic end bulb)

A

The enlarged bottom of a somatic motor neuron

51
Q

Voltage gated calcium ion channel

A

A channel that is gated by calcium and has permeability for calcium ions (Ca2+)

52
Q

Acetylcholine vesicles

A

A vesicles that carries acetylcholine

53
Q

Acetylcholine (ACh)

A

A neurotransmitter

54
Q

Synaptic cleft

A

The space between the axon terminal and the muscle fiber

55
Q

Motor end plate

A

The part of a neuromuscular junction that touches the nerve fiber

56
Q

Junctions folds

A

Invaginations that increase the surface area of the sarcolemma

57
Q

Ligand gated sodium ion channel

A

A channel that is opened and closed by a ligand

58
Q

Aceytlcholinesterase

A

An enzyme that hydrolyzes acetylcholine

59
Q

Graded potential

A

Temporary changes in the membrane voltage

60
Q

What does the duration of a muscle contraction depend on?

A

Duration of nerve action potential

Number of calcium ions in the sarcoplasm

Availability of ATP

61
Q

During relaxation, a fall in calcium ion concentration allows for what?

A

Calcium ions to detach from troponin (TnC)

Myosin binding site on actin are re-covered by tropomyosin

62
Q

What factors contribute to the return to resting length?

A

Tendons stretch sarcomeres back to resting length

Antagonist or gravity reverse direction of original motion

63
Q

What is rigor mortis?

A

A fixed muscular contraction involving all skeletal muscles after death that lasts until lysosomal enzymes are released by autolysis

*Begins 2-7 hours after death, ends in 1-6 days

64
Q

What causes rigor mortis?

A

Lack of ATP

Calcium build up in the sarcoplasm

Calcium ion ATPase pumps stop working

SR membrane breaks down

65
Q

Motor unit

A

One somatic motor neuron and all the skeletal muscles that it controls

66
Q

What controls how precise a movement is?

A

The ratio of number of muscle fibers to one motor neuron

*Fewer muscle fibers per somatic motor neuron indicates a more controlled movement

67
Q

Length-tension relationship

A

Resting length at time of stimulation

Determines degree of overlap and number of pivoting cross bridges

68
Q

Frequency of stimulation

A

Number of stimuli per unit time

Affects concentration of calcium ions in the sarcoplasm and bound to troponin

69
Q

Twitch

A

A single stimulus-contraction-relaxation sequence

  • Duration depends upon the type and location of muscle, and internal/external environment conditions
  • 7-100 milliseconds
70
Q

What are the three phases of a twitch?

A

Latent (lag) period, contraction period, relaxation period

71
Q

Latent (lag) period

A

Begins at stimulation and lasts 2 milliseconds

Excitation-contraction coupling (cross-bridges) occurrs

72
Q

Contraction period

A

Tension rises to a peak and contraction cycle begins

Lasts 10-100 milliseconds

Myosin power strokes

73
Q

Relaxation period

A

Relaxation cycle begins

Lasts 10-100 milliseconds

Myosin cocks

74
Q

Treppe

A

A stair-step increase in twitch tension that occurs when skeletal muscle fibers are stimulated a second time immediately after the relaxation phase ends, resulting in a contraction with slightly higher than that of the first

Tension will increase over first 30-50 stimulations but will eventually plateau

75
Q

Wave summation

A

Successive stimuli arrive before the relaxation phase has been completed

Duration of a single twitch determines the max time available for wave summation

76
Q

Incomplete tetanus (unfused tetany)

A

Stimulus frequency increases further without allowing the muscle to relax completely

Tension rises further and reaches a peak

77
Q

Complete tetanus (fused tetany)

A

Stimulus frequency is so high that the relaxation phase is eliminated and tension plateaus at maximum levels

*Full muscle contraction

78
Q

Multiple motor unit summation (recruitment)

A

Increasing the strength of the stimulus by increasing the number of stimulated motor units

79
Q

Subthreshold stimulus

A

Stimulus strength is too low and no contraction occurs

80
Q

Threshold stimulus

A

Stimulus at which the first observable contraction occurs

81
Q

Submaximal stimuli

A

Progressive increase in stimulus strength

82
Q

Maximal stimulus

A

Strongest stimulus at which all of the muscle’s motor units are recruited

83
Q

Supramaximal stimuli

A

No real change from increasing stimulus strength since maximal motor units are already working

84
Q

Synchronous motor unit summation

A

Peak tension that occurs when all motor units in the muscle contract in a state of complete tetanus

*Very brief because individual muscle fibers use up all available energy reserves

85
Q

Asynchronous motor unit summation

A

Sustained contraction in which motor units are activated on a rotating basis

*Prolongs strong contraction by preventing or delaying fatigue

86
Q

Muscle tone

A

Normal tension and firmness of a resting muscle

  • Some motor units are always active to keep the muscle firm and healthy, but this does not produce an active movement
  • Higher muscle tone accelerates the recruitment process during voluntary contraction
  • Stabilizes positions of bones and joints
  • Increases metabolic rate
87
Q

Isotonic contraction

A

A muscle contraction that maintains constant tension in the muscle as the muscle changes length

Muscle’s max force of contraction > total load on the muscle

*Thin filaments are sliding

88
Q

Concentric isotonic contraction

A

Peak muscle tension > load

Muscle shortens and decreases angle at joint and moves the load

Tension remains constant at a value just above the load

*EX. Bicep curl up

89
Q

Eccentric isotonic contraction

A

Peak muscle tension < load

Muscle elongates and exerts precise control over the amount of tension and rate of elongation

*EX. Bicep curl down

90
Q

Isometric contraction

A

The muscle as a whole does not change length and results in no motion

Occurs when the muscle isn’t strong enough to move the load

Peak muscle tension < load

  • Cross-bridges generate force, but do not move thin filaments
  • EX. Muscles that maintain upright posture or hold joints stationary
91
Q

How does myokinase make ATP?

A

Removes 1 phosphate from ADP and adds it to another ADP, resulting in 1 AMP and 1 ATP

92
Q

Aerobic endurance

A

The length of time a muscle can continue to contract using aerobic pathways

93
Q

Anaerobic threshold

A

The point at which muscle metabolism converts to anaerobic pathways

94
Q

Phosphagen system:

Description
Energy source
Oxygen use
Products
Duration of energy
A

Coupled reaction of creatine phosphate and ADP

Creatine phosphate

None

1 ATP, creatine

15 seconds

95
Q

Creatine phosphate

A

A high-energy molecule stored in muscles much more abundantly than ATP

*Replenished during rest

96
Q

Anaerobic pathway:

Description
Energy source
Oxygen use
Products
Duration of energy
A

Glycolysis and lactic acidosis formation

Glucose

None

2 ATP, lactic acid

30-40 seconds

97
Q

Aerobic pathway:

Description
Energy source
Oxygen use
Products
Duration of energy
A

Aerobic cellular respiration

Glucose, pyruvic acid, fatty acids, amino acids

Required

32 ATP, CO2, H2O

Hours

98
Q

Force

A

The maximum amount of tension produced

99
Q

Endurance

A

The amount of time an activity can be sustained

100
Q

What do both force and endurance depend on?

A

The type of muscle fibers and physical conditioning

101
Q

Fast glycolytic (FG) fibers

Energy pathways (metabolism) 
Myoglobin
Mitochondria 
Glycogen 
Capillaries 
Fatigue resistance
Myosin ATPase activity
Color
A

🚭Anaerobic glycolysis

⬇️Low myoglobin

⬇️Few mitochondria

🔺High glycogen

⬇️Few capillaries

⏩⏩Contract quickly, fatigue quickly

⏩Fast myosin ATPase

🤍Pale muscle fibers

102
Q

Fast oxidative (FOG) fibers

Energy pathways (metabolism) 
Myoglobin
Mitochondria 
Glycogen 
Capillaries 
Fatigue resistance
Myosin ATPase activity
Color
A

🚭🌬Anaerobic glycolysis, aerobic respiration

🔺High myoglobin

🔺Many mitochondria

🔺High glycogen

🔺Many capillaries

⏩⏯Contract quickly, fatigue slower

⏩Fast myosin ATPase

💗❤️Pink-red muscle fibers

103
Q

Slow oxidative (SO) fibers

Energy pathways (metabolism) 
Myoglobin
Mitochondria 
Glycogen 
Capillaries 
Fatigue resistance
Myosin ATPase activity
Color
A

🌬Aerobic respiration

🔺High myoglobin

🔺Many mitochondria

⬇️Low glycogen

🔺Many capillaries

⏸⏸Contract slowly, fatigue slowly

⏸Slow myosin ATPase

♥️Red muscle fibers

104
Q

Hypertrophy

A

Muscle growth from heavy training

105
Q

Atrophy

A

Muscle shrinkage from lack of activity

106
Q

Disuse atrophy

A

Atrophy due to lack of use

107
Q

Denervation atrophy

A

Atrophy due to damaged nerves that are unable to send action potentials to activate the muscle

108
Q

Duchenne muscular dystrophy

A

A fatal degenerative disease causing muscles to weaken due to inability to produce dystrophin

109
Q

Myasthenia

A

General muscular weakness due to a reduction in ACh receptors on the motor end plate

110
Q

Fibromyalgia

A

Chronic disorder of widespread pain, fatigue, and tenderness

111
Q

Central/Psychological fatigue

A

Exhaustion and pain

112
Q

Muscle fatigue

A

Physiologically inability to contract or produce tension

113
Q

What can muscle fatigue be caused by?

A

Depletion of metabolic reserves

Damage to sarcolemma or myofibrils

Insufficient oxygen supply

Buildup of lactic acid

Depletion of ACh (nerve AP fails to release it)

114
Q

Recovery period

A

Time required after exertion for muscles to return to normal

115
Q

What happens during the recovery period?

A

Oxygen becomes available

Mitochondrial activity restores energy reserves

Repairs made to skeletal muscle fibers

116
Q

Cori cycle

A

Returning lactate to the liver

Returning glucose back to muscle cells

117
Q

Oxygen debt

Excess post exercise oxygen consumption, EPOC

A

Heavy breathing resulting from increased oxygen demand to normalize metabolic rates

BIOL 223 Lecture (26 decks)

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