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Musculoskeletal (transes) > 4.09 Physiology and Molecular Biology of Muscle > Flashcards

4.09 Physiology and Molecular Biology of Muscle Flashcards

1
Q

Highly specialized cells for the conversion of chemical energy to mechanical energy

A

Muscle

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2
Q

Muscles produce action potential from __

A

stimulation that is transmitted along the cell membranes

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3
Q

Three kinds of muscles

A

skeletal
cardiac
smooth/visceral

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4
Q

Characteristics of the three kinds of muscles

contorl mode, anatomic, histological

A

skeletal: voluntary, striated
cardiac: involuntary, striated
visceral: involuntary, smooth

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5
Q

T/F. Skeletal muscle is able to contract even in the absence of nervous stimulation, if the circumstance is in need of contraction.

A

False. (assuming normality)

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6
Q

T/F. There are no anatomic.functional connection between the individual muscle fibers.

A

True

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7
Q

Term that pertains to one muscle fiber

A

Myocyte

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8
Q

Term that pertains to one muscle fiber bundle

A

Fasciculus

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9
Q

Term that pertains to a group of fascicles

A

Muscle tissue

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10
Q

Skeletal muscles begin and end in __

A

Tendons

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11
Q

What is the implication of the parallel orientation of the muscles and its tendons?

A

Force of contraction of the units will be additive

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12
Q

Layer of connective tissue that surrounds the muscles binding it to the external organ structures

A

Fascia

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13
Q

Connective tissue lining that ensheathes each fiber

A

Endomysium

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14
Q

Connective tissue lining that ensheathes each fascicle

A

Perimysium

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15
Q

Connective tissue lining that ensheathes each muscle

A

Epimysium

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16
Q

True cellular membrane of the muscle fiber

A

Sarcolemma

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17
Q

Term for the shrinkage of muscles

A

Atrophy

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18
Q

Term for the enlargement of muscles

A

Hypertrophy

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19
Q

A state where the rate of synthesis is much higher than the rate of degradation of muscle contractile proteins results to:

A

Hypertrophy

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20
Q

State at which the rate of degradation of contractile proteins becomes greater than the rate of replacement results to:

A

Atrophy

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21
Q

T/F. All skeletal muscles have their nuclei in the periphery of cells.

A

False. 3-10% have central nuclei (the younger ones)

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22
Q

Disease where the nuclei of skeletal muscles are found in the center of the cell

A

Centronuclear myopathy

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23
Q

Basic contractile unit of the muscle

A

Sarcomere

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24
Q

Where are mitochondria found in muscle fibers?

A

Below and in-between myofibrils

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25
Q

Why are the I-bands lighter in color than A-bands?

A

Because of the absence of myosin

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26
Q

Dark protein band that transects the middle of the I-band

A

Z-line

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27
Q

What is the relationship between a sarcomere and the Z-line?

A

The area in between two adjacent Z-lines is a sarcomere

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28
Q

Wide, dark band surrounding the H-zone and M-line

A

A-band

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29
Q

Light band zone bisecting the A-band

A

H-zone

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30
Q

Dark line bisecting the H-zone

A

M-line

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31
Q

What makes up the thick filament?

A

Myosin

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32
Q

What is the gross structure of the myosin?

A

Two heavy chain heads, each with two light chains

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33
Q

What are the two light chains of the two heavy chains?

A

alkali and regulatory

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34
Q

The myosin-binding site of actin is covered by what?

A

tropomyosin-troponin complex

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35
Q

Lighter filament with two intertwined chains that pas through grooves between two actin chains

A

Tropomyosin

36
Q

Connected to tropomyosin every 7th molecule of actin

A

Troponin

37
Q

Component of troponin that binds with tropomyosin

A

Troponin T

38
Q

Component of troponin that binds with calcium ions

A

Troponin C

39
Q

Component of troponin that inhibits actin-myosin interaction; hides binding site

A

Troponin I

40
Q

Muscular filament that prevents overextension of sarcomeres and maintains central location of A bands

A

Titin

41
Q

T/F. Nebulin can serve as a mechanoreceptor and influence gene expression and protein degradation in a mechanical activity-dependent manner.

A

False. Not nebulin, but titin.

42
Q

Muscular filament that stabilizes thin filament length during muscle development

A

Nebulin

43
Q

Muscular filament anchors thin filaments to structure of Z-lines

A

alpha-actinin

44
Q

Muscular filament that participates in transfer of force from the contractile system to the outside of the cells

A

Dystrophin

45
Q

What anchors dystrophin to the sarcolemma?

A

Integrins

46
Q

What has bee the most common cause of muscle dystrophy?

A

Dystrophin abnomality

47
Q

Muscular fiber that forms a link between integrins and the dystrophin

A

Laminin

48
Q

T/F. Laminin links integrins and dystrophin from the EXTERNAL of the cell

A

True

49
Q

How does the dystrophin-glycoprotein complex add strength to the muscle?

A

By providing a scaffolding for the fibrils and connecting them to the extracellular environment

50
Q

What composes the motor unit?

A

Anterior horn cell and its muscle/motor fibers

51
Q

What is the role of the sarcoplasmic reticulum?

A

Stores and pumps calcium ions

52
Q

Electrical/mechanical

Excitation is __ while contraction is __

A

electrical

mechanical

53
Q

Discuss what happens after the junction

A
  1. increase in calcium - entry intro pre-synapse
  2. synaptotagmin and SNAREs allow exocytosis of acetylcholine in vesicles
  3. acetylcholine reaches synaptic cleft and goes to its receptor
  4. conformational change to open sodium channels and allow sodium to enter (action potential)
  5. choline broken down from acetylcholine to discontinue the signal
54
Q

What causes the breakdown of acetylcholine?

A

Acetylcholinesterase

55
Q

What composes a triad?

A

T-tubule and two adjacent terminal cisternae in aluminum junction

56
Q

Through which does the sarcoplasmic reticulum release calcium ions?

A

Ryanodine receptors

57
Q

Enlarged region of the sarcoplasmic reticulum that stores calcium

A

Terminal Cisterna

58
Q

What does the terminal cisternae that weakly binds calcium?

A

Calsequestrin

59
Q

Invagination of the sarcolemma in between two terminal cisternae

A

Transverse tubule

60
Q

For what is the T-tubules?

A

Rapid transmission of action potential

61
Q

What are the receptors involved in the coupling of excitation and contraction?

A 
Dihydropyridine receptor (DHPR)
Ryanodine receptor (RYR)
62
Q

These are voltage sensors that respond to T tubule action potential

A

Dihydropyridine receptor

63
Q

Where are these embedded?

  1. DHPR
  2. RYR
A
  1. T-tubule membrane

2. Terminal cisterna of the sarcoplasmic reticulum

64
Q

Disorder that causes runaway release of calcium, which leads to a tremendous amount of calcium release and sustained uncontrolled muscle contraction.

A

Malignant hyperpyrexia/hyperthermia

65
Q

Steps in the actin-myosin interaction

A
  1. Myosin with ADp and inorganic phosphate
  2. Released calcium combines with TnC and induces a conformational change –> power stroke –> exposure of the myosin binding site
  3. Myosin head binds to exposed area on actin –> release of ADP and Pi
  4. ATP binding makes myosin head release actin
  5. ATP hydrolyzed to ADP and Pi returns myosin to resting state
66
Q

It is a Ca2+ ATPase that transfers Ca2+ from the cytosol of the cell to the lumen of the SR at the expense of ATP hydrolysis during muscle relaxation

A

Sarco/Endoplasmic Reticulum Calcium-ATPase (SERCA)

67
Q

Dysfunction of the SERCA or depleted ATP will keep the myosin bound to actin and result in __

A

Contractures, rigor mortis

68
Q

Three possible energy sources for muscle contraction

A

Creatine phosphate
Carbohydrates
Fatty acids and TAGS

69
Q

Immediate high-energy and major source to replenish ATP supply

A

Creatine phosphate

70
Q

Depletion of creatine phosphate store causes __

A

skeletal muscle fatigue

71
Q

Processing of creatine phosphate (cleaving of) is mediated by __.

A

Creatine phosphokinase

72
Q

Elevated CPK level in the blood is considered to result from __

A

Tissue damage

73
Q

Carbohydrates replenish __

A

ATP stores

74
Q

Mechanical activity that comes before electrical activity

A

Muscle twitch

75
Q

Muscles can be classified according to muscle twitch based on __

A

Speed of contraction

76
Q

Differentiate slow and fast twitch according to:

Fiber type, twitch duration, fatigability, color, metabolism, mitochondria, glycogen

A 
Slow - fast
Type I - type II
100 ms - 7.5 ms
Resistant - fatigable
Red (myoglobin) - white (low myoglobin)
Oxidative - glycolytic
High - fewer
Low - high
77
Q

Response a skeletal muscle to a single stimulation

A

Twitch

78
Q

Time when impulse is traveling along the sarcolemma and down the T-tubules to SR

A

Latent period

79
Q

State of twitch when tension increases

A

Contraction period

80
Q

State of twitch when muscle relaxes and tends to return to its original length

A

Relaxation period

81
Q

What does motor unit summation imply?

A

Degree of contraction of a skeletal muscle is influenced by the number of motor units being stimulated

82
Q

What does the concept of wave summation mean?

A

An increase in the frequency with which a muscle is stimulated increases the strength of contraction

83
Q

If a muscle fiber is stimulated so rapidly that it doesn’t relax at all between stimuli, __ occurs

A

Tetanus

84
Q

Gradual increase in stimulus strength as muscle contracts

A

Treppe

85
Q

T/F. Muscle disease is proximal, most of the time.

A

True

Musculoskeletal (transes) (6 decks)

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