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Group Craniofacial Histology > Lecture 8 Muscle Physiology > Flashcards

Lecture 8 Muscle Physiology Flashcards

1
Q

How long are muscle cells?

A

As long as the whole muscle

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2
Q

What kind of nucleation does skeletal muscle have?

A

multinucleated

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3
Q

How do muscle cells become a multinucleated syncitium?

A

By fusing myoblasts together into muscle fibers

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4
Q

T/F CT around and within skeletal muscle is continuous with the CT of bones.

A

True

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5
Q

What are the CT layers from the endomysium of muscle to the periosteum of bone?

A

Endo-peri-epi-deep fascia-tendon-periosteum

Mnemonic: Every Person Eats Donuts for The Paste

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6
Q

What are the series-elastic components of the musculoskeletal system?

A

All of the interconnected tissues in muscles that are attached to the bone membrane from endomysium to the periosteum

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7
Q

What is the specialized plasma membrane of muscle cells?

A

Sarcolemma

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8
Q

The sarcolemma is _______ at rest.

A

Polarized

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9
Q

What can depolarize the sarcolemma?

A

Acetylcholine released by motor neurons

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10
Q

What are the tubular infoldings of the sarcolemma?

A

T-tubules (transverse tubules)

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11
Q

What do T-tubules do?

A

Penetrate into the cell and carry the electrochemical current into the cell

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12
Q

What is sarcoplasm made of?

A

Highly organized myofibrils (actin and myosin), glycogen, and myoglobin

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13
Q

What does glycogen do in the sarcoplasm? What does myoglobin do in the sarcoplasm?

A

Stores energy. Stores oxygen

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14
Q

What is the specialized endoplasmic reticulum of muscle cells?

A

Sarcoplasmic reticulum

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15
Q

What storage sacs is the sarcoplasmic reticulum connected to? What do these sacs store?

A

Termincal cisternae. They store calcium ions

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16
Q

What protein complex anchors myofibrils inside muscle cells?

A

Dystrophin

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17
Q

How does dystrophin attach myofibrils to the endomysium?

A

Dystrophin attaches the myofibrils next to the sarcolemma to integral membrane proteins that extend into the endomysium

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18
Q

What is the difference between the sarcolemma, sarcoplasm, and sarcoplasmic reticulum?

A

Sarcolemma is the outer plasma membrane of muscle cells.
Sarcoplasm is the cytosol (flesh)
Sarcoplasmic reticulum is the series of interconnected tubules connected to the terminal cisternae

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19
Q

Are the T-tubules of the sarcolemma and the interconnected tubules of the sarcoplasmic reticulum the same thing?

A

No. The T-tubules are larger invaginations of the sarcolemma. The t-tubules are surrounded on either side by the terminal cisternae. The terminal cisternae are interconnected by the tubules of the sarcoplasmic reticulum

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20
Q

What is the triad formed surrounding the myofibrils?

A

The T-tubule surrounded on either side by the calcium storing terminal cisternae

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21
Q

T/F The sarcolemma is surrounded by the endomysium.

A

True. Endomysium surrounds individual muscle cells made of myofibrils

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22
Q

What is the difference between a myofiber and a myofibril?

A

The myofiber is the muscle cell which is composed of myofibrils making up its cytoplasm (sarcoplasm)

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23
Q

What are the three bands of a sarcomere?

A

A band, H band, and I band

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24
Q

Which of the three sarcomere bands does not change in size?

A

A band is the length of the thick myosin filaments

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25
Q

Which sarcomere band changes in size and is a region of pure myosin? Pure actin?

A

H band is pure myosin. I band is pure actin

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26
Q

What starts a wave of depolarization in the muscle cell?

A

The binding of ACh to the AChR (acetylchone receptor)

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27
Q

How far does the wave of depolarization spread over the sarcolemma?

A

The sarcolemma down to the T-tubules

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28
Q

Where are calcium channels found that open to release calcium on the sarcomeres?

A

On the sarcoplasmic reticulum buried deep among the myofibrils

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29
Q

What must calcium bind to for the release of tropomyosin off of the active sites on actin?

A

Troponin

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30
Q

What do the AHM I Z regions of the sarcomere stand for?

A 
A anisotropic (dark appearance of myosin)
H helle (german for bright) region of myosin w/o actin
M middle
I Isotropic (light appearance of actin)
Z Zwischen (german for between) anchor site of titin
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31
Q

T/F Thin filaments are globular subunits. Myosin is composed of two entwined polypeptides each shaped like a golf club

A

True

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32
Q

The heads of myosin can also be called which enzyme?

A

ATPase

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33
Q

Are actin and myosin filaments elastic?

A

No, They stay the same size

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34
Q

If actin and myosin are not elastic how are they considered contractile?

A

Because they contract the cell (myofiber) by moving over each other in a series of sarcomeres

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35
Q

Which muscle filament is elastic?

A

Titin

36
Q

Where are the cell bodies of somatic motor neurons?

A

Brainstem and spinal cord

37
Q

What is the range of branching in the axons of motor neurons?

A

From 3-6 to over 200 branches

38
Q

T/F Each axon branch of a somatic motor neuron contacts one muscle fiber (cell)

A

True

39
Q

What is a motor unit?

A

A motor neuron and all the muscle fibers it innervates

40
Q

What kind of control are small motor units good for? Large motor units?

A

Fine control (eye muscles). Strength (can have as many as 1000 muscle fibers per nerve fiber)

41
Q

Much of the intracellular protein is _______ (anionic or cationic

A

anionic

42
Q

What four actions are involved in Muscle contraction and relaxation?

A
  1. Excitation
  2. Excitation-Contraction Coupling
  3. Contraction
  4. Relaxation
43
Q

What is excitation-contraction coupling?

A

action potentials on the sarcolemma activate myofilaments

44
Q

How is the resting membrane potential disrupted?

A

When ligand-gated Na+ channels on the motor end plate bind to ACh and open to let Na+ into the cell which depolarizes the membrane

45
Q

During the powerstroke in which direction does the myosin head pull the thin actin filament relative to the z line?

A

Towards the Z line

46
Q

With out ATP where is the myosin head relative to the active site of the actin?

A

The myosin head is bound to the active site of actin

47
Q

T/F ATP is required for the myosin head to release actin.

A

True

48
Q

During Rigor Mortis, where does the Ca++ come from to activate the actin-myosin cross bridges?

A

The SR releases Ca++ as it deteriorates

49
Q

What molecule is needed for the myosin to bind with the actin? What molecule is needed for the myosin to release the actin?

A

Ca++. ATP

50
Q

How does Botox work?

A

It blocks the ACh release from motor neurons. Muscles cannot contract to cause wrinkles in those areas

51
Q

What are paralytic neuromuscular toxins?

A

Muscle relaxants such as Botox, Curare, TTX

52
Q

What are spasmodic neuromuscular toxins?

A

Muscle stimulants that cause uncontrollable muscle contraction and spasms

53
Q

What is the role of glycine in muscle contraction?

A

It prevents overstimulation of muscles

54
Q

Which autoimmune disease mimics the effects of curare?

A

Myasthenia Gravis

55
Q

How does myasthenia gravis inhibit the generation of an end-plate potential?

A

Antibodies bind and inhibit ACh receptors from sensing ACh

56
Q

How is myasthenia gravis treated?

A

With acetylcholinesterase inhibitors, thymus removal or immunosuppressive agents

57
Q

What is the only source of energy for muscle contraction?

A

ATP

58
Q

Which enzyme system regenerates ATP from ADP and Pi?

A

Phosphagen enzyme system.

59
Q

What are the two main phosphogen enzymes?

A

Myokinase and Creatine Kinase

60
Q

Where does myokinase get its Pi in ATP formation?

A

From ADP producing ATP and AMP

61
Q

Where does creatine kinase get its Pi for ATP formation?

A

Creatine phosphate

62
Q

Where does the immediate source of ATP come from? How long does the immediate source provide ATP?

A

Aerobic metabolism using O2 released from myoglobin in muscles. Also, from Phosphagen system. Lasts about 10 seconds

63
Q

Where does the short-term energy source of ATP come from? How long does it last?

A

Anerobic metabolism thru the glycogen-lactic acid system? Lasts for about 30-40 seconds

64
Q

Where does the long term energy source of ATP come from? When does it begin?

A

Respiratory and cardiovascular systems catch up to the O2 demand for aerobic respiration. Begins after 40 seconds of sustained exercise and supplies more than 90% of ATP at this stage

65
Q

Which muscle fiber type has lots of myoglobin and syntesizes ATP aerobically?

A

Red Slow Twitch (Type 1)

66
Q

Which muscle fiber type uses anaerobic metabolism to produce ATP? Which one uses both anaerobic and aerobic metabolism?

A

White Fast Twitch (Type IIb). Pink Intermediate (Type IIa)

67
Q

Which muscle type has striated muscle cells linked to each other by intercalated discs?

A

Cardiac muscle

68
Q

What junctions line the intercalated discs?

A

Gap junctions and desmosomes

69
Q

What do gap junctions facilitate in cardiac muscle?

A

The facilitate the synchronization of muscle contractions

70
Q

Where does the Ca++ come from in cardiac muscle? What facilitates the Ca++ absorption?

A

From the extracellular fluid. Large T-tubules

71
Q

Which striated muscle type forms triads of the SR with the T-tubules? Which one forms diads?

A

Triads are formed in skeletal muscle where the T-tubule is sandwiched between two terminal ciseternae of the SR. Diads are formed in cardiac muscle - the T-tubule is paired with the SR only on one side

72
Q

What kind of respiration does cardiac muscle use almost exclusively?

A

Aerobic. Cardiac muscle is an obligate aerobe

73
Q

How are damaged cardiac cells repaired?

A

By fibrosis not mitosis.

74
Q

Which muscle cells are fusiform and have only one nucleus?

A

Smooth muscles

75
Q

What kind of nucleation does cardiac muscle have in humans? (mono or multi-nucleated)

A

Mononucleated just like smooth muscle. Skeletal muscle is multinucleated

76
Q

Where do the thin filaments attach to in smooth muscles?

A

Dense bodies scattered throughout the sarcoplasm, which are attached to dense plaques on the sarcolemma

77
Q

T/F Both cardiac and smooth muscles can be described as a functional syncitium

A

True. They both are mononucleated but have gap junctions that allows depolarization to spread from cell to cell

78
Q

Where does smooth muscle get its Ca++ for contractions?

A

From a poorly developed SR and extracellular fluid

79
Q

What does the poorly developed SR have instead of T-tubules?

A

Caveolae which are shallow invaginations of the SR

80
Q

What doe stretching do to smooth muscles?

A

Opens mechanically-gated calcium channels causing contraction

81
Q

What happens when smooth muscle is stretched gently?

A

It briefly contracts and then relaxes

82
Q

How can smooth muscle be made to contract forcefully?

A

By being stretched greatly. The contraction force matches the degree of stretching.

83
Q

T/F Smooth muscles responds to hormones, low pH, and high CO2

A

True

84
Q

What regulatory protein must calcium bind to in the cytoplasm of smooth muscle in order to activate the MLCK?

A

Calmodulin

85
Q

What is MLCK?

A

Myosin light chain kinase. It uses ATP to phosphorylate the myosin head

86
Q

What do the actin thin filaments pull on to shorten Smooth muscle?

A

the interconnected dense bodies which may be seen as the Z discs in skeletal muscles

87
Q

How many ATP are needed for the power stroke in smooth muscle?

A

Two ATP. One used by the MLCK to activate the myosin head and a second to ratchet the myosin head causing contraction

Group Craniofacial Histology (9 decks)

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