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Physiology Block 5 > Muscle > Flashcards

Muscle Flashcards

1
Q

Muscle makes up ______ of mass in humans

A

30-50%

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2
Q

What are the two types of striated muscle

A

Skeletal and cardiac

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3
Q

What is the non striated muscle type

A

Smooth

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4
Q

What is the only voluntary muscle type

A

Skeletal

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5
Q

Where is the site of most ANS innervation and function

A

Smooth muscle

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6
Q

What is the order of how a muscle is packed?

A

Muscle-fascicles-fibers(myocyte)-sarcomeres

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7
Q

Long, thin cell with multiple nuclei and many myofibrils

A

Muscle fiber (myocytes)

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8
Q

What is the muscle cytoplasm

A

Sarcoplasm, lots of mitochondria

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9
Q

What does each myofibril consist of

A

Many sarcomeres surrounded by the sarcoplasmic reticulum and T tubule system

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10
Q

Highly organized contractile and structural proteins

A

Sarcomeres

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11
Q

What muscle type does not have sarcomeres

A

Smooth

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12
Q

Thick and thin filaments

A

Contractile proteins

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13
Q

Thick filament

A

Myosin

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14
Q

What does myosin consist of

A
  • intertwined heavy chains with globular heads

- heads bind actin and have ATPase activity

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15
Q

What is the makeup of actin

A

2 strands of F actin in a helix

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16
Q

What is F actin made of

A

Many G actin molecules

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17
Q

Where are hte myosin binding sites

A

Actin

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18
Q

Double stranded helix around actin. Covers the myosin binding site

A

Tropomyosin, regulatory

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19
Q

What is bound to tropomyosin

A

Troponin complex

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20
Q

Troponin T (TnT)

A

Binds the complex to tropomyosin

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21
Q

Troponin I (TnI)

A
  • inhibitory

- holds tropomyosin in the myosin binding site

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22
Q

Troponin C (TnC0

A

Binds calcium, uncovers myosin binding site

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23
Q

Connect sarcomeres to sarcolemma and ECM

A

Dystrophin

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24
Q

What is the most common mutation that causes muscular dystrophy

A

Mutations in dystrophin

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25
Q

Holds thin filaments apart from one another

A

Nebulae

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26
Q

Holds thin filaments to z-disc

A

Alpha-actinin

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27
Q

Spring that runs though heavy chain and connects it to the z disc

A

Titan

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28
Q

Bisects the sarcomeres and bare zone, structural proteins that hold thick filaments in place

A

M line

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29
Q

Only heavy chains

A

Bare (H) zone

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30
Q

Thick and thin filaments, dark striations

A

A band

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31
Q

Only thin filaments, light striations

A

I band

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32
Q

Connects individual sarcomeres, bisects I band

A

Z-disc

33
Q

Functional unit of muscle

A

Sarcomeres

34
Q

Smallest part of muscle that can still perform its function, to contract and generate force

A

Sarcomeres

35
Q

How does the sarcomeres shorten when stimulated

A
  • actin is pulled towards M line
  • bare zone gets smaller
  • occurs along length of myofibril, fiber, fascicle, and muscle- causes movement
36
Q

____ discs move closer together during sarcomeres contraction

A

Z disc

37
Q

What happens to I band when sarcomeres contracts

A

Gets smaller

38
Q

What happens to A band when sarcomere contracts

A

Stays the same

39
Q

Where does the soarcolemma membrane cross myocyte

A

Between myofibrils

40
Q

Myocytes are arranged to handle

A

Calcium to help depolarization of whole muscle as a unit

41
Q

What is within the sarcolemma membrane

A
  • T tubules

- dihydropyridine receptor (DHPR, voltage gated calcium channel)

42
Q

____ stores calcium in the sarcolemma

A

Sarcoplamic reticulum

43
Q

How does sarcoplasmic reticulum store calcium

A
  • has SERCA (Ca2+-ATPase)
  • most prevalent in the longitudinal SR
  • pumps Ca2+ in, stores it to keep sarcoplasmic Ca2+ low
44
Q

How does the SR run along the myofibrils

A

Parallel

45
Q

What are the ends of the SR called

A

Terminal cisternae

46
Q

What is special about the terminal cisternae?

A
  • end of the SR

- has a ryanodine receptor (RyR, calcium release channel)

47
Q

Where does the t tubule meet the SR?

A

In the triad

48
Q

What is the triad

A

2 terminal cisternae, one t tubule

49
Q

DHPR, RyR, and SR in relation to T tubule in skeletal muscle

A

All VERY close together along the T tubule system

ONLY IN SKELTAL MUSCLE,

50
Q

Changes in the DHPR shape affect ____

A

RyR shape

51
Q

What keeps free calcium low in the SR

A

Calcium binding proteins

52
Q

Where does calcium reuptake occur

A

Longitudinal sections

53
Q

Where does calcium release occur

A

Terminal areas

54
Q

What are the steps of excitation in skeletal muscles

A
  1. AP in muscle membrane
    2a. Depolarization of T tubules
    2b. Opens SR Ca2+ release channels
  2. Increased intracellular Ca2+ cxn
  3. Ca2+ binds troponin C
  4. Tropomyosin moves and allows interaction of actin and myosin
  5. Cross bridge cycling and force generation
  6. Ca2+ reaccumulated by SR—relaxation
55
Q

Actions potential in the NMJ

A

Depolarizes down sarcolemma membrane and T tubules system

56
Q

How does AP affect DPHR and RyR?

A

Causes confromational change in DPHR, whihc causes a change in RyR conformation and opens it

57
Q

What does the opening of the RyR allow

A

Ca2+ from SR into cytosol

58
Q

What does calcium bind once it is in the cytosol

A

TnC and causes contraction

59
Q

How does calcium binding TnC cause contraction

A
  • moves tropomyosin off binding pocket

- cross bridges cycling and force generation occurs

60
Q

What sequesters Ca2+ in the SR

A

SERCA

61
Q

When does relaxation occur

A

When tropomyosin moves back over binding site

62
Q

Cross bridge cycling

A

Myosin binds actin and pulls it towards the M-line

63
Q

Sliding filament theory

A
  • actin and myosin slide past one another
  • pulls z discs together, pulls sarcomeres together
  • force is transferred to the connective tissue surrounded fiber
  • eventually entire muscle shortens and moves bones
64
Q

Myosin binding site at rest

A

Covered by tropomyosin

65
Q

When myosin binds ATP

A

Myosin becomes cocked and has high affinity for actin

66
Q

What causes tropomyosin to move off of binding site?

A

Calcium binding TnC

67
Q

Once binding site is free and myosin binds ATP, what happens

A

Myosin finishes hydrolysis ATP and ADP and binds to actin

68
Q

Once myosin is bound to actin

A

Myosin undergoes a conformation change, releases ADP and ‘ratchets”, this pulls the actin towards M-line

Power stroke

69
Q

Myosin affinity for actin once it binds ATP

A

Lowered actin affinity

70
Q

What happens once myosin binds ATP

A

Releases actin, partially hydroluyzes ATP and is recocked.

71
Q

Cross bridging will repeat as long as what is available

A

Calcium and ATP

72
Q

Relaxation

A
  • Ca2+ resequesered into SR by SERCA
  • TnC no longer bound to Ca2+
  • tropomyosin covers actin binding site
  • contraction stops and muscle can relax
73
Q

Rigor Morris occurs shortly after death, what is the most direct cause

A

Lack of ATP, myosin cant break down without ATP

74
Q

Malignant hyperthermia is potentially fatal genetic disorder characterized by hyper responsiveness to inhaled anesthetics. It results in elevated body temp, skeletal muscle rigidity, and lactic acidosis

Which of the following molecular changes could account for these clinical manifestations?

A

Prolonged opening of the RyR channel

Dumps Ca2+ and causes lots of contractions

75
Q

What makes a motor unit

A

Neuron and all synapses myocytes

76
Q

What leads to fine movements, such as EMO

A

Fewer cells per nerve

77
Q

Each time a motor neuron fires, you get a _____

A

Muscle twitch

  • a single AP
  • a single generation of force
78
Q

Single twitch in a single motor unit

A

Not sufficient for movement

79
Q

Mechanism of tetanus

A

Increase twitches by recruiting more units (spatial) or stimulate the same unit numerous times (temporal)
-temporal works because there is a lag between excitation and force generation

Physiology Block 5 (8 decks)

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