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A&P 1 > Skeletal Muscle > Flashcards

Skeletal Muscle Flashcards

1
Q

Muscle Fasciculus are

A

the individual bundles of muscle fibers in a skeletal muscle

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2
Q

Muscle Fibers consist of

A

a single muscle cell

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3
Q

Myofibrils are made up of

A

thick and thin myofilaments giving muscle its striped appearance

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4
Q

Myofilaments consist of

A

thick fillaments (myosin), thin filaments (actin) and elastic filaments (titans)

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5
Q

Skeletal muscle fiber size

A

extends the tntire lenght of a muscle, 10-80 micrometers in diameter

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6
Q

How many muscles does one nerve innervate?

A

One, usuall in the midele of the fiber

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7
Q

What encapsulates a muscle fiber?

A

the sarcolemma

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8
Q

What is a muscle fiber made up of?

A

contains 100s to 1000s of myofibrils

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9
Q

Myofibrils contain more of what than what?

A

More actin than myosin

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10
Q

What does the Sarcoplasma contain?

A

Glycosomes (membrane-enclosed organelle that contains glycolytic enzymes), Myoglobin-Oxygen, Mitochondria, Calcium

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11
Q

What type of proteins are myofilaments?

A

Polymerized proteins

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12
Q

Actin:

A

3000 filaments, Thin filaments, Light I bands

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13
Q

Myosin:

A

1500 filaments, Thick filaments, Dark A bands

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14
Q

What is a sarcomere

A

the portion of myofibril between 2 consecutive Z-discs (gets smaller and larger depending on contraction)

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15
Q

What are Z-discs made of?

A

structural proteins

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16
Q

Wehre do Z-discs attach

A

to the ends of actin

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17
Q

What do Z-discs interdigate with

A

myosin

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18
Q

Puropose of Z-discs

A

attach myofibrils together along the entire muscle fiber

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19
Q

What does a Titan do?

A

keeps actin and myosin in place

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20
Q

Titan size

A

BIG protein - molecular weight of 3 million

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21
Q

How does a titan work?

A

Titans are springy, the elastic end attaches to the Z-disc and the other end is tethered to myosin thick filament

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22
Q

what are A bands?

A

mysin (thick filament) + ends of actin (thin filament)

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23
Q

what are I bands?

A

actin (thin filament)

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24
Q

what is the H zone?

A

just myosin, middle / zero interaction with actin

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25
Q

what is a Z-disk?

A

structure of the myofibril (ends of actin/interdigitates myosin)

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26
Q

What is the M line

A

within the H zone; M = “mittelscheibe” = “middle” of sarcomere

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27
Q

What is a Titan

A

springy framework holding myosin in place

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28
Q

How many polypeptide chains does a myosin molecule have?

A

6

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29
Q

How many heavy chains does a myosin molecule have?

A

2 (MW = 200,000)

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30
Q

How many light chains does a myosin molecule have?

A

4 (MW = 20,000)

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31
Q

What configuration are myosin heavy chins in?

A

double helix (tail, ends fold bilaterally into globulare polypeptide structures = heads)

32
Q

Describe the myosin light chains

A

4 light chains are part of the myosin heads (2 per head)

33
Q

What does Calsequestrin do

A

Binds with Ca++ in the sarcoplasmic reticulum attracting it towards the channels for quick exit when needed

34
Q

What are two things the myosin light chains do

A

*#1: help control the function of the head during contraction
*#2: functions as an ATP enzyme

35
Q

How many molecules make up myosin?

A

200+

36
Q

How long is myosin filament

A

1.6 micrometers in length

37
Q

Muscle from big to small

A

Muscle - muscle fascicles - muscle fibers - myofibrils (made of many sarcomeres) - myofilaments (made of actin, myosin, titan)

38
Q

What are myofilaments made of?

A

actin, myosin, and titans

39
Q

What are myofibrils made of?

A

many sarcomeres

40
Q

What is Actin made up of?

A

2 F-actin molecules twisted like a helix - have G-actin molecules “active sites”

41
Q

What does tropomyosin do?

A

Spirals around F-actin covering the “active sites” (G-actin molecules “G sites”)

42
Q

Troponin I has an affinity for:

A

Actin

43
Q

Troponin T has an affinity for:

A

Tropomyosin

44
Q

Troponin C has an affinity for:

A

Calcium

45
Q

3 sources of energy

A

*1: Rephosphorylation of ATP (phosphocreatine-donates phosphate group to convert ADP to ATP)
*2: Glycolysis (restores phosphocreatinine, direct energy for contraction in absence of O2, 2.5x faster than “foodstuff method”
*3: Oxidative Metabolism (O2 + foodstuff = ATP)

46
Q

One motor uniti is innervated by a single nerve fiber, how many muscle fibers are in each motor unit?

A

80-100 muscle fibers/motor unit

47
Q

What is the motor end plate coverd by?

A

Schwann Cells (protection from surrounding enviornment)

48
Q

What is the Synaptic Gutter?

A

Invagination caused by the nerve ending on the membrane layer

49
Q

What is a Synaptic Cleft?

A

Space between terminal & fiber membrane (25 nanometers)

50
Q

How does Choline enter the axon?

A

Via the Choline Transporter (CHT), sodium also enters with it

51
Q

What is needed to synthesize (ACh)?

A

Acetyl CoA + Choline (and an enzyme)

52
Q

What enzyme catalyzes synthesis of ACh?

A

Choline Acetyltransferase (CAT)

53
Q

What moves ACh vesicles to the nerve terminal?

A

Vesicular Acetylcholine Transporter (VAT)

54
Q

When ACh is released, what 2 things can happen?

A

*1: It attaches to a receptor
*2: It is degraded

55
Q

What degrades ACh in the synaptic cleft?

A

Acetylcholinesterase cleaves ACh into Choline + Acetate

56
Q

What degrades ACh in plasma

A

Pseudocholinesterase

57
Q

How are new vesicles formed?

A

After AP, “coated pits” appear in the nerve terminal and clathrin protein contracts forming new vesicles in the terminal

58
Q

What are ACh vesicles attracted too in the nerve terminal?

A

Dense Bars

59
Q

What allows ACh vesicles to attach to the pre-synaptic cleft and exocitose?

A

Ca++/Calmodulin dependent protein kinase that has beeen activated by calcium

60
Q

How many ACh attach to an ACh receptor to create a conformational change (activation)

A

2

61
Q

What charge does the ACh receptor have and what does it do?

A

Negative charge - repels negative ions and attracts positive such as Na+ (VIP)

62
Q

Adult ACh is comprised of what subunits?

A

2x alpha
1 beta
1delta
1episilon

63
Q

Fetal ACh is comprised of what subunits?

A

2x alpha
1 beta
1 delta
1 gamma

64
Q

What allows action potentials depolarize the entire muscle?

A

Transverse tubules (T-tubuels)

65
Q

What sections is the Sarcoplasmic reticulum divided into?

A

Terminal Cisternae and
Longitudinal Tubules

66
Q

An important voltage gated channel often targeted by calcium channel blockers:

A

Dihydropyridine receptor (DHP)

67
Q

Receptor on the SR targeted by Dantrolene:

A

Ryanodine receptor

68
Q

Two receptors that work together to release calcium from the SR in skeletal muscle:

A

Dihydropyridine receptor
Ryanodien receptor

69
Q

What do Desmosomes do?

A

Prevent sheering of cell connections

70
Q

What do Connexins do?

A

Form intercellular gap junctions (channels that mediate direct signaling between cells)

71
Q

What causes muscle fatigue?

A

glycogen depletion, bloodflow interruption

72
Q

What causes Rigor Mortis?

A

ATP is all utilized. No more present to trigger release of myosin

73
Q

How long until Rigor Mortis relaxes?

A

15-25 hours due to protien deterioration (myosin no longer connected)

74
Q

How long is an AP in skeletal muscle?

A

1 - 5 milliseconds (5x longer than large myelinated nerves)

75
Q
A

A&P 1 (10 decks)

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