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140 . foundations of anatomy and clinical practice > Muscles > Flashcards

Muscles Flashcards

1
Q

What are the functions of muscles?

A

Produce movement
Stabilise body positions
Store and move substances (myocardium)
Generate heat

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2
Q

What is thermogenesis?

A

The process of generating heat as a result of muscle contraction

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3
Q

What is the importance of thermogenesis?

A

Maintain body temperature

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4
Q

What are the key properties of muscle tissue?

A

Electrical excitability
Contractility
Extensibility
Elasticity

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5
Q

Explain the muscle property of electrical excitability:

A

Respond to electrical stimuli (action potentials) cause contraction of the muscle

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6
Q

Explain the muscle property of contractility:

A

The muscles have the ability to shorten creating tension causing movement

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7
Q

Explain the muscle property of extensibility:

A

Myocardium and smooth muscle can relax and extend when required

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8
Q

Explain the muscle property of elasticity:

A

Muscles can return to their original position after stretching

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9
Q

What are the different types of muscle tissue?

A

Cardiac
Smooth
Skeletal

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10
Q

Where is smooth muscle located?

A

Within the walls of hollow internal organs, e.g. blood vessels, airways and abdominal organs

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11
Q

Smooth muscle is non-striated, what does this mean?

A

There is no specific tissue pattern

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12
Q

Smooth muscle is non-voluntary, what does this mean?

A

It is innervated by neurons in the autonomic nervous system so muscle contraction is non voluntary

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13
Q

Compare / Contrast the 3 muscle types in relation to voluntary contraction:

A 
Cardiac = involuntary
Smooth = involuntary
Skeletal = voluntary
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14
Q

Compare / Contrast the 3 muscle types in relation to striation:

A 
Cardiac = striated
Smooth = non-striated
Skeletal = striated
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15
Q

Where is cardiac muscle tissue found?

A

Only in the heart, especially the walls of the heart

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16
Q

Cardiac muscle is striated, what does this mean?

A

The muscle proteins are formed in well organised bundles (sarcomeres)

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17
Q

Cardiac muscle is involuntary, what does this mean?

A

The muscle is stimulated by the Sinoatrial node which creates the action potential for contraction to begin

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18
Q

Where are Intercalated discs found and what is their function?

A

Found in cardiac muscle, they aid in transmitting action potentials through myocardium to increase contraction

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19
Q

Skeletal muscle is striated, what does this mean?

A

The muscle proteins are formed in an organised fashion, through alternating dark and white bands

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20
Q

Skeletal muscle is voluntary, what does this mean?

A

Contraction is controlled by neurons as part of the somatic nervous system (although most contractions are subconscious)

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21
Q

Compare / Contrast the 3 muscle types in relation to contraction speed:

A 
Cardiac = moderate
Smooth = slow
Skeletal = fast
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22
Q

Compare / Contrast the 3 muscle types in relation to size:

A 
Cardiac = Large
Smooth = Small
Skeletal = Very large
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23
Q

Compare / Contrast the 3 muscle types in relation to regulator proteins for contraction:

A 
Cardiac = Troponin and Tropomyosin
Smooth = Calmodulin and Myosin
Skeletal = Troponin and Tropomyosin
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24
Q

Compare / Contrast the 3 muscle types in relation to autorhythmicity:

A 
Cardiac = Yes
Smooth = Yes
Skeletal = No
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25
Q

What is a sarcolemma?

A

An excitable plasma membrane surrounding a muscle fiber

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26
Q

What is sarcoplasm?

A

The cytoplasm of the muscle fiber

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27
Q

Where is the sarcoplasm found?

A

Within the sarcolemma

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28
Q

What substances are found within sarcoplasm which aid muscular contraction?

A

Glycogen (for ATP)

Myoglobin (O2 receiver)

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29
Q

What is the function of mitochondria in muscle fibers?

A

They breakdown glycogen into ATP

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30
Q

Many myofibers combine to form a _____:

A

Muscle fiber

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31
Q

What are sarcomeres?

A

The smallest component of a myofiber

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32
Q

What are the main contractile proteins of a myofiber?

A

Myosin (thick filament)

Actin (thin filament)

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33
Q

What is the M line?

A

The middle of a sarcomere

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34
Q

What is the Z disc?

A

The end of a sarcomere

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35
Q

What is the A band?

A

The middle of the sarcomere extending the entire length of the thick filament (myosin), including overlap

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36
Q

What is the H zone?

A

The area of sarcomere where there is thick filament (myosin) only, so not the overlap area

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37
Q

In relation to M and Z, what happens during muscle contraction?

A

Z discs are pulled towards the M line, shortening the sarcomere

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38
Q

What is the I band?

A

The area of sarcomere where there is thin filament (actin) only, so not the overlap area

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39
Q

In a myofiber, what is the name for the protein in the THIN filament?

A

Actin

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40
Q

Which protein moves the Z disc towards the M line?

A

Actin (thin filament)

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41
Q

What is the structure of the thick filament?

A 
Myosin tail
Myosin head (containing Actin-binding site and ATP-binding site)
42
Q

What occurs during the second stage of the sliding filament theory?

A

Attachment of myosin to actin:
Myosin in the high-energy conformation attach to actin’s binding site
Forming a cross bridge

43
Q

What is the position of tropomyosin during a relaxed state?

A

It covers the myosin-binding site on the tin filament actin proteins

44
Q

What causes troponin to become active?

A

Binding with calcium ions

45
Q

What are the steps in the sliding filament theory?

A

ATP hydrolysis
Attachment of myosin to actin
Power stroke
Detachment of myosin from actin

46
Q

What occurs during the first stage of the sliding filament theory?

A

ATP hydrolysis:
ATP attached to the ATP-binding site on myosin
ATP -> ADP + Pi (+energy)
Energy is stored in the myosin head
Head cocked into high-energy conformation (90 degrees)

47
Q

What happens when calcium binds with troponin?

A

A change in the actin occurs moving the tropomyosin off the myosin-binding site allowing the myosin to bind to the actin

48
Q

What is the structure of the thin filament?

A

Two actin strands helically around each other, clumps of troponin, myosin-binding site covered by tropomyosin

49
Q

In a myofiber, what is the name for the protein in the THICK filament?

A

Myosin

50
Q

What occurs during the fourth stage of the sliding filament theory?

A

Detachment of myosin from actin:
ATP attaches to myosin head
Link between actin and myosin weakens
Cross bridge detaches and actin slides back

51
Q

What occurs during the third stage of the sliding filament theory?

A

Power stroke:
Pi is released initiating power stroke
Myosin head pivots and pulls actin towards M line
Then ATP is released

52
Q

The sliding filament theory is continuous as long as what conditions are present?

A

There is sufficient ATP in the sarcoplasm and there is stimuli from the nervous system to contract

53
Q

What are contractile proteins?

A

Proteins which generate force during muscle contractions

Myosin, Actin

54
Q

What are regulatory proteins?

A

Proteins which help control the muscle contraction process

Tropomyosin, Troponin

55
Q

What are structural proteins?

A

Proteins that maintain the alignment of the thick and thin filaments, provide myofibril elasticity and link myofibrils to sarcolemma
(Titin, α-Actinin, Myomesin, Nebulin, Dystrophin)

56
Q

Where are regulatory proteins Tropomyosin and Troponin found?

A

On the thin filament (actin)

57
Q

Explain how regulatory proteins aid muscle contraction:

A

When calcium ions bind to troponin, it changes shape and subsequently moves tropomyosin away from the myosin-binding site allowing myosin to bind to actin

58
Q

Where are transverse tubules?

A

Run from the sarcolemma into the individual muscle fibres

59
Q

Where are calcium ions located prior to their binding with troponin?

A

In the terminal cisterns of the sarcoplasmic reticulum

60
Q

How do calcium ions get into the sarcoplasm from sarcoplasmic reticulum?

A

Through calcium release channels controlled by voltage

61
Q

How do calcium ions get into the sarcoplasmic reticulum from the sarcoplasm?

A

Through the Calcium-ATPase pump

62
Q

How does an action potential from a neuron trigger the contraction of a muscle?

A

The action potential travels down the transverse tubule and opens the voltage gated channels to release calcium into the sarcoplasm and sliding filament theory begins

63
Q

Where does stimulation of the sarcolemma occur?

A

Neuromuscular junction

64
Q

What is a neuromuscular junction?

A

The point where a somatic motor neuron meets a muscle fiber

65
Q

What neurotransmitter diffuses across the synaptic cleft at the neuromuscular junction?

A

Acetylcholine (ACh)

66
Q

Explain the process of synaptic transmission at the neuromuscular junction:

A

Acetylcholine (ACh) released from vesicle into synaptic cleft
Diffuses across and binds to ACh receptors
Muscle action potential is produced by release of sodium
ACh is broken down

67
Q

When is Acetylcholine ACh broken down in synaptic transmission?

A

When there are no longer impulses coming down the axon terminal of the somatic motor neuron

68
Q

What is a motor neuron consisted of?

A

A somatic motor neuron plus all of the muscle fibers it stimulates

69
Q

When Acetylcholine (ACh) binds to the ACh receptors in the junctional fold, which ion is released to begin the muscular contraction?

A

Sodium / Na+

70
Q

An action potential down one somatic neuron will stimulate how many muscle fibers?

A

It varies, averagely around 180 muscle fibers. It will stimulate all muscle fibers supplied by that neuron

71
Q

How do muscle fibers reduce fatigue and allow recovery of other fibres?

A

Not all fibers within a muscle belly are contracted at the same time, some contract while others rest

72
Q

What happens to suitable motor unit recruitment efficiency with age?

A

We learn how to recruit the fewest fibers to perform a function to allow other fibres to rest as fully as possible

73
Q

What is wave summation?

A

When a second action potential occurs before the first muscle fibers have finished with contraction

74
Q

What is unfused tetanus?

A

Multiple action potentials are generated, but there is relaxation of muscle fibers between so the contraction force is increased at a jagged rate

75
Q

What is fused tetanus?

A

Many consecutive stimuli are sent per second, this produces a steady, sustained force of contraction

76
Q

What is the relationship between number of action potentials and force of contraction?

A

More action potentials leads to a greater force of contraction

77
Q

Explain what is meant by the Muscle Length-Tension Relationship:

A

The forcefulness of a contraction depends on the zone of overlap between thick and thin filaments

78
Q

Why would a fully contracted or fully rested sarcomere contract with less force than one partially contracted?

A

There is less overlap between the thick and thin filaments

79
Q

What is meant by muscle tone?

A

The tension in the relaxed muscle

80
Q

How is muscle tone maintained?

A

A small number of fibers act in uniform (contract and relax)

81
Q

When is muscle tone lost and the muscle is considered ‘flaccid’?

A

When there is injury to the nervous system

82
Q

What are the different types of muscle contraction?

A

Isotonic Eccentric
Isotonic Concentric
Isometric

83
Q

What is the difference between an isotonic and isometric contraction?

A 
Isotonic = Tension remains constant as muscle length decreases or increases
Isometric = Tension increases greatly without a change in muscle length
84
Q

What are the different types of muscle fibers?

A 
Slow oxidative (SO) fibers
Fast oxidative-glycolytic (FOG) fibers
Fast glycolytic (FG) fibers
85
Q

Compare the myoglobin content of the different muscle fibers:

A 
SO = many
FOG = many
FG = few
86
Q

Compare the mitochondria content of the different muscle fibers:

A 
SO = many
FOG = many
FG = few
87
Q

Compare the colour of the different muscle fibers:

A 
SO = red
FOG = red-pink
FG = white
88
Q

Compare the capillaries of the different muscle fibers:

A 
SO = many
FOG = many
FG = few
89
Q

Compare the ATP generating capacities of the different muscle fibers:

A 
SO = high, by aerobic respiration
FOG = intermediate, aerobic respiration and anaerobic glycolysis
FG = low, by anaerobic glycolysis
90
Q

Compare the creatine kinase store of the different muscle fibers:

A 
SO = low
FOG = intermediate
FG = high
91
Q

Compare the glycogen store of the different muscle fibers:

A 
SO = low
FOG = intermediate
FG = high
92
Q

Compare the contraction velocity (speed) of the different muscle fibers:

A 
SO = slow
FOG = fast
FG = fast
93
Q

Compare the fatigue resistance of the different muscle fibers:

A 
SO = high
FOG = intermediate
FG = low
94
Q

Compare the rate of ATP hydrolysis of the different muscle fibers:

A 
SO = slow
FOG = fast
FG = fast
95
Q

How is ATP generated in slow oxidative (SO) fibers?

A

Aerobic respiration

96
Q

What is the order of recruitment of the different muscle fibers?

A 
first = slow oxidative (SO)
second = fast oxidative-glycolytic (FOG)
third = fast glycolytic (FG)
97
Q

What is the primary function of slow oxidative (SO) fibers?

A

Maintaining posture and aerobic endurance

98
Q

How is ATP generated in fast oxidative-glycolytic (FOG) fibers?

A

Aerobic respiration and anaerobic glycolysis

99
Q

What is the primary function of fast oxidative-glycolytic (FOG) fibers?

A

Walking, sprinting

100
Q

What is the primary function of fast glycolytic (FG) fibers?

A

Rapid movements of short durations

140 . foundations of anatomy and clinical practice (12 decks)

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