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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
Why are the I-bands lighter in color than A-bands?
Because of the absence of myosin
26
Dark protein band that transects the middle of the I-band
Z-line
27
What is the relationship between a sarcomere and the Z-line?
The area in between two adjacent Z-lines is a sarcomere
28
Wide, dark band surrounding the H-zone and M-line
A-band
29
Light band zone bisecting the A-band
H-zone
30
Dark line bisecting the H-zone
M-line
31
What makes up the thick filament?
Myosin
32
What is the gross structure of the myosin?
Two heavy chain heads, each with two light chains
33
What are the two light chains of the two heavy chains?
alkali and regulatory
34
The myosin-binding site of actin is covered by what?
tropomyosin-troponin complex
35
Lighter filament with two intertwined chains that pas through grooves between two actin chains
Tropomyosin
36
Connected to tropomyosin every 7th molecule of actin
Troponin
37
Component of troponin that binds with tropomyosin
Troponin T
38
Component of troponin that binds with calcium ions
Troponin C
39
Component of troponin that inhibits actin-myosin interaction; hides binding site
Troponin I
40
Muscular filament that prevents overextension of sarcomeres and maintains central location of A bands
Titin
41
T/F. Nebulin can serve as a mechanoreceptor and influence gene expression and protein degradation in a mechanical activity-dependent manner.
False. Not nebulin, but titin.
42
Muscular filament that stabilizes thin filament length during muscle development
Nebulin
43
Muscular filament anchors thin filaments to structure of Z-lines
alpha-actinin
44
Muscular filament that participates in transfer of force from the contractile system to the outside of the cells
Dystrophin
45
What anchors dystrophin to the sarcolemma?
Integrins
46
What has bee the most common cause of muscle dystrophy?
Dystrophin abnomality
47
Muscular fiber that forms a link between integrins and the dystrophin
Laminin
48
T/F. Laminin links integrins and dystrophin from the EXTERNAL of the cell
True
49
How does the dystrophin-glycoprotein complex add strength to the muscle?
By providing a scaffolding for the fibrils and connecting them to the extracellular environment
50
What composes the motor unit?
Anterior horn cell and its muscle/motor fibers
51
What is the role of the sarcoplasmic reticulum?
Stores and pumps calcium ions
52
Electrical/mechanical | Excitation is __ while contraction is __
electrical | mechanical
53
Discuss what happens after the junction
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
What causes the breakdown of acetylcholine?
Acetylcholinesterase
55
What composes a triad?
T-tubule and two adjacent terminal cisternae in aluminum junction
56
Through which does the sarcoplasmic reticulum release calcium ions?
Ryanodine receptors
57
Enlarged region of the sarcoplasmic reticulum that stores calcium
Terminal Cisterna
58
What does the terminal cisternae that weakly binds calcium?
Calsequestrin
59
Invagination of the sarcolemma in between two terminal cisternae
Transverse tubule
60
For what is the T-tubules?
Rapid transmission of action potential
61
What are the receptors involved in the coupling of excitation and contraction?
``` Dihydropyridine receptor (DHPR) Ryanodine receptor (RYR) ```
62
These are voltage sensors that respond to T tubule action potential
Dihydropyridine receptor
63
Where are these embedded? 1. DHPR 2. RYR
1. T-tubule membrane | 2. Terminal cisterna of the sarcoplasmic reticulum
64
Disorder that causes runaway release of calcium, which leads to a tremendous amount of calcium release and sustained uncontrolled muscle contraction.
Malignant hyperpyrexia/hyperthermia
65
Steps in the actin-myosin interaction
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
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
Sarco/Endoplasmic Reticulum Calcium-ATPase (SERCA)
67
Dysfunction of the SERCA or depleted ATP will keep the myosin bound to actin and result in __
Contractures, rigor mortis
68
Three possible energy sources for muscle contraction
Creatine phosphate Carbohydrates Fatty acids and TAGS
69
Immediate high-energy and major source to replenish ATP supply
Creatine phosphate
70
Depletion of creatine phosphate store causes __
skeletal muscle fatigue
71
Processing of creatine phosphate (cleaving of) is mediated by __.
Creatine phosphokinase
72
Elevated CPK level in the blood is considered to result from __
Tissue damage
73
Carbohydrates replenish __
ATP stores
74
Mechanical activity that comes before electrical activity
Muscle twitch
75
Muscles can be classified according to muscle twitch based on __
Speed of contraction
76
Differentiate slow and fast twitch according to: | Fiber type, twitch duration, fatigability, color, metabolism, mitochondria, glycogen
``` 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
Response a skeletal muscle to a single stimulation
Twitch
78
Time when impulse is traveling along the sarcolemma and down the T-tubules to SR
Latent period
79
State of twitch when tension increases
Contraction period
80
State of twitch when muscle relaxes and tends to return to its original length
Relaxation period
81
What does motor unit summation imply?
Degree of contraction of a skeletal muscle is influenced by the number of motor units being stimulated
82
What does the concept of wave summation mean?
An increase in the frequency with which a muscle is stimulated increases the strength of contraction
83
If a muscle fiber is stimulated so rapidly that it doesn't relax at all between stimuli, __ occurs
Tetanus
84
Gradual increase in stimulus strength as muscle contracts
Treppe
85
T/F. Muscle disease is proximal, most of the time.
True

Musculoskeletal (transes) (6 decks)

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