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Anatomy of muscles Flashcards

1
Q

What are 3 different types of muscles?

A

Skeletal
Cardiac
Smooth

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2
Q

what is skeletal muscle made of ?

A

Muscle fibres (MYOCYTE/ Muscle cell)

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3
Q

What are muscle fibres made of?

A

Myofibrils

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4
Q

What do myocytes have?

A

nuclei

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5
Q

What is Epimysium?

A

connective tissue layer around muscle

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6
Q

What is Perimysium?

A

layer of connective tissue around Fascicle

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7
Q

What is Fascicle ?

A

bundles of muscle fibres inside muscle

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8
Q

What is Endomysium?

A

layer of connective tissue around each muscle fibre

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9
Q

What are Satellite cells?

A

stem cells of muscle between basal lamina

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10
Q

what does connective tissue form?

A

supporting tissue so blood vessels/nerves can run in

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11
Q

are skeletal muscle fibres multinucleated?

A

YES

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12
Q

How are muscle fibres formed?

A

myoblasts fusing together

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13
Q

What are myofibril composed of?

A

Sarcomeres in series

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14
Q

Where does 1 sarcomere run from?

A

Z disk to adjacent Z disk

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15
Q

What is A Band?

A

distance between thick filament of same sarcomere

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16
Q

Does the Width of A band change?

A

NO

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17
Q

What is I band?

A

thin filaments , distance between ends of different sarcomeres

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18
Q

What is H band?

A

region between thin filament protrusions

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19
Q

What happens in sarcomere on contraction?

A

I and H band Shortens

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20
Q

What is Z line?

A

where thin filaments attach

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21
Q

What is M line?

A

middle region

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22
Q

What powers muscle contraction?

A

cross-bridges

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23
Q

What determines the amount of contraction force?

A

amount of overlap between myofibrils

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24
Q

What is a thick filament?

A

myosin with tail and 2 heads

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25
What activity does myosin head have?
ATPase- hydrolyse ATP to ADP+Phosphate for Actin binding
26
When does Myosin bind to actin ?
Power stroke
27
When is Actin released from ?
Hydrolysis of ATP
28
When does recovery stroke occur?
when actin is released
29
what do 2 heavy chains in the tail form?
coiled coil
30
What is 2 globular head formed from?
2 light chains each
31
How many light chains in myosin?
4 light chains
32
How does head bind to actin?
2 motor domains
33
What are 2 types of light chain?
Regulatory and Essential
34
What is myosin arrangement?
anti parallel
35
What do myosin tails assemble into?
thick filaments
36
What is major protein in thin filament?
ACTIN
37
What other proteins in thin filaments?
``` Tropomyosin Troponin Nebulin Alpha Actinin Myosin ```
38
where are thin filaments anchored ?
Z Disc
39
What are barbed ends in Z disc cross linked by?
Alpha actinin
40
Where are pointed ends in M line capped by?
Tropomodulin protein
41
What is barbed end capped by ?
Capping protein T
42
What do capping proteins do?
regulate length of the precise filaments and ensures right polarity
43
What polarity does barbed end in Z disk match?
half of the thick filament
44
What do cross bridges on myosin filament do to actin?
pull thin filament into middle of sarcomere
45
What does force of contraction depend on?
sarcomere length
46
What is the plateau region in sarcomere shortening?
full overlap of thick and thin filaments
47
What is the structure of Tropomyosin?
alpha helical coiled coil
48
How many actin subunits for 1 tropomyosin?
7
49
What does Ca2+ bind to?
troponin and tropomyosin moves from myosin binding site
50
How many actin subunits for 1 troponin?
7
51
What happens at low Ca2+?
actin binding sites for myosin are blocked
52
What happens at high Ca2+?
contraction - binds to TnC of troponin and tropomyosin moves across actin - myosin binding site on actin is exposed
53
What is Titin? (largest protein in body from Z to M line?
Carries tension from 1 sarcomere to another
54
What titin regulate?
thick filament length and restores overlap
55
What does Nebulin do?
bind across thin filament and regulate thin filament length
56
What does the Sarcolemma have?
T tubules
57
what are T tubules associated with?
Sarcoplasmic reticulum
58
When is Ca2+ released from Sarcoplasmic reticulum?
when muscle is depolarised
59
What does Ca2+ bind to?
troponin
60
What is Calsequesturin ?
Hold Ca2+ in Sarcoplasmic reticulum cisterna
61
Where does Action potential pass in depolarisation of muscle fibres?
t tubules to Ca2+ stores
62
How is action potential in nerve terminal transmitted to muscle ?
acetylcholine released and bind to receptors in membrane
63
What is DHPR (dihydropyridine) receptor?
on T tubules and Ca2+ channel
64
What does DHPR activate?
a RYR (ryanodine receptor) so release Ca2+ from SR
65
What is RYR?
Ca induced Ca release receptor so
66
How is Ca2+ removed from sarcoplasm after contraction?
ATP dependant Ca2+ pump and back into Sarcoplasmic reticulum
67
How does the muscle stay relaxed?
low Ca2+ by ATP pumps in Sarcoplasmic reticulum
68
What nervous system causes muscle contraction?
Sympathetic nervous system
69
What is released at neuromuscular junction?
Acetyl choline - binds to nicotinic cholinergic receptors so action potential within Sarcolemma - AP down T tubules and activates DHPR and so RyR so Ca2+ spike
70
What does Ca2+ spike cause?
conformational change in Troponin Tm unit so myosin binding and sarcomere shortening
71
What happens when frequency of AP is increased?
stronger contraction since summation of tension
72
What happens if AP are too frequent?
Fused tension so muscle cant relax
73
Why does muscle twitch happen?
delay for contraction since time for Ca2+ to bind to troponin
74
What do large motor neurones innervate?
larger motor units
75
What are ATP sources?
Creatine Phosphate Glycolysis Oxidative Phosphorylation
76
What the type of Muscle Fibres?
Type 1 fibres - slow and anaerobic | Type 2 fibres- fast and anaerobic
77
What are the transmissions of forces?
longitudinal | Lateral
78
What is longitudinal trans. of force along fibre?
myosin crossbridges and titin carry tension from one sarcomere to the next
79
What is Lateral trans. of force along fibre?
Costamere link Z disk to sarcolemma
80
What do the Myofibrillar proteins have?
cytoskeleton so all sarcomeres connected

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