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BMS150 Midterm 2 > Physiology of Skeletal Muscles 1 > Flashcards

Physiology of Skeletal Muscles 1 Flashcards

1
Q

Skeletal muscles are composed of bundles of _______.

A

Fascicles

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2
Q

Each fascicle is composed of _______.

A

Linearly aligned muscle fibers

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3
Q

What kind of cell is a muscle fiber?

A

A single multi-nucleated, elongated cell

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4
Q

Each muscle fiber is composed of many _______, arranged linearly

A

Sarcomeres

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5
Q

Connective tissue surrounding the whole muscle?

A

Epimysium

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6
Q

Sheath surrounding each fascicle?

A

Perimysium

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7
Q

Sheath surrounding the individual muscle fibers?

A

Endomysium

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8
Q

What is below the endomysium?

A

Sarcolemma = cell membrane of the muscle cell

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9
Q

Each myofibril is composed of many ________.

A

Myofilaments

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10
Q

Myofilaments are composed of what?

A
  • Contractile proteins
  • Regulatory proteins
  • Additional accessory proteins
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11
Q

Contractile proteins?

A
  • Actin
  • Myosin
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12
Q

Regulatory proteins?

A
  • Tropomyosin
  • Troponin
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13
Q

What forms the contractile unit of skeletal muscle?

A

Sarcomeres

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14
Q

Sarcomeres are composed of interdigitating myofilaments made up of what?

A
  • Thin filaments (actin)
  • Thick filaments (myosin)
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15
Q

What are the bounds of each sarcomere?

A

Z-disk

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16
Q

What structures attach to the Z disk?

A
  • Thin filaments
  • Proteins involved in stretch sensing and signal communication
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17
Q

What is at the center of the sarcomere?

A

M-line

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18
Q

Regions of thin filament that don’t overlap with thick filament?

A

Light I bands

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19
Q

Regions of thick filament that don’t overlap thin filament?

A

H-zone

20
Q

Region where the thick and thin filaments do overlap?

A

Dark A bands

21
Q

What shortens during muscle contraction? What stays the same?

A

Shorten = I band and H-zone
Same = A band

22
Q

Actin monomer? Polymer?

A

Monomer = G-actin
Polymer = F-actin

23
Q

What are thin filaments composed of?

A

Two strands of F-actin wound together

24
Q

Each G-actin has a binding site for _______

A

myosin

25
Q

Head region of myosin forms _________ that interact with adjacent actin filaments

A

Cross-bridges

26
Q

Many myosin units are arranged in staggered positions to form what?

A

Thick filament

27
Q

Important biochemical features of myosin head

A
  • ATPase activity
  • Actin-binding region
  • ATP binding region
28
Q

regulatory molecule that prevents cross-bridge formation between myosin and actin in a relaxed muscle

A

Tropomyosin

29
Q

Troponin complex subunits? What do they bind to?

A
  • Troponin C - binds calcium
  • Troponin T - binds tropomyosin
  • Troponin I - binds actin and inhibits contraction
30
Q

When Ca binds to Troponin C, this causes ________ to pull ______ and _______ off of myosin-binding site of G-actin subunits

A

Troponin T; Tropomyosin and Troponin I

31
Q

Sarcolemma contains invaginations called ______

A

Transverse tubules (T-tubules)

32
Q

What is the purpose of T-tubules?

A

Allows the action potential to be carried deep into the muscle fiber

33
Q

What do the sarcolemma and T-tubules associate closely with? What is it?

A

Sarcoplasmic reticulum = specialized ER that has high [Ca]

34
Q

What is the terminal cisternae?

A

Specialized regions of the SR that associate with T-tubules

35
Q

Junction between T-tubules and SR cisterna?

A

Muscle triad

36
Q

What is the neuromuscular junction?

A

Synapse where a motor nerve axon contacts each muscle fiber near the middle of the fiber

37
Q

The region of the sarcolemma in closest contact with the presynaptic nerve terminal is called the…?

A

Motor end plate

38
Q

The motor nerve terminal releases ______ which binds to the _______ receptor on the sarcolemma

A

Acetylcholine; nicotinic

39
Q

Action potential propagate along the T tubules and activate ________ channels in the sarcolemma

A

L-type Ca2+ channels

39
Q

What is the purpose of the T-tubule in action potential propagation?

A

It brings the action potential deep within very large muscle fibers

40
Q

Activation of the L-type Ca2+ channels triggers ______ activation of what kind of receptors?

A

Mechanical activation of Ryanodine receptors

41
Q

Most of the Ca2+ that activates the skeletal muscle sarcomere is from what?

A

Sarcoplasmic reticulum

42
Q

A single action potential for a motor neuron that barely causes any force development in the muscle fiber group?

A

Twitch

43
Q

Development of force (tension) in a muscle due to many action potentials that causes a greater release of Ca from the SR?

A

Tetany

44
Q

What is fused tetany?

A

Maximal force development in the muscle fibers of a motor unit = no individual “twitches” visible

BMS150 Midterm 2 (14 decks)

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