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Neuroscience > Muscle Physiology ( Neuro) > Flashcards

Muscle Physiology ( Neuro) Flashcards

1
Q

What are the name of the proteins found in muscles that slide past each other to allow movement?

A

Actin and myosin

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2
Q

What types of muscles are Striated?

A

Cardiac Muscle and Skeletal muscle

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3
Q

What type of muscles has involuntary movement ?

A

Cardiac and Smooth muscle

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4
Q

True or False? Skeletal muscle has Voluntary movement.

A

TRUE!!

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5
Q

Where are smooth muscles found?

A

Single unit muscles - hollow visceral organs (digestive tract
,bladder, uterus, various ducts of glands &blood vessels

Multi-unit muscles - Intrinsic eye, air ways, large arteries

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6
Q

What is the name of the connective tissue layer that surrounds each muscle fascicle(bundle of cells/fibres)?

A

Perimysium

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7
Q

What is the name of the connective tissue layer that surrounds each muscle cell and is also found between fibres?

A

Endomysium

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8
Q

What is the name of the connective tissue layer that becomes the muscle sheath that fuses with the tendon?

A

Epimysium

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9
Q

What is the basic functional unit of muscle contraction?

A

The sacromere

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10
Q

Fill in the blanks. “The sarcomere has T tubules which form at
junction of_____and ____.

A

I and A bands

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11
Q

True or False? In skeletal muscles ,myosin filaments attach indirectly to Z-line via protein called Nebulin ( for stability).

A

FALSE!! Myosin filaments attach via the protein Titin( for stability)

“MY TITI’s are stable”

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12
Q

Fill in the blanks.” Actin filaments are directly attached to the Z-line, and arranged along inflexible protein named ______( for inelasticity.”

A

Nebulin.

A- actin A - asthma needs to be NEBULIzed - N- Nebulin

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13
Q

True or False? Smooth muscles contains Sarcomere.

A

FALSE!! They contain SARCOPLASM

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14
Q

What Is the name of the structure that surrounds sarcoplasm?

A

Sarcolemma

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15
Q

What is the name of the structure found in smooth muscles that act as signalling pathways and has pinocytotic structures which transport fluid & electrolyte into the cell?

A

Caveolae

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16
Q

True or False. There are no T- tubules present in smooth muscles.

A

TRUE!!!

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17
Q

What is the distinct feature of Cardiac muscle?

A

It contains Intercalated Discs

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18
Q

Fill in the blanks . Cardiac muscle contains _______ in the fibres while skeletal muscle contains ______ in their fibres.

A

Cardiac - Diads
SkeleTal - Triads( 1 T tubules + 2 terminal cisternae )

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19
Q

What is the name of the structure that stores Calcium ions?

A

Terminal cisternae in Sarcoplasmic reticulum

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20
Q

What are the events that take place once Ca2+ are released into the sarcoplasm?

A
  1. Actin active-site exposure
  2. Cross-bridge attachment
  3. Pivoting of myosin head
  4. Cross-bridge detachment
  5. Myosin reactivation
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21
Q

Where are Dihydropyridine receptors found?

A

In the Sarcollemal membrane

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22
Q

Where are ryanodine receptors found?

A

In the sarcoplasmic reticulum

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23
Q

What happens in the Actin active-site exposure stage?

A
  • In this stage, The released Ca2+ binds to Troponin C.
  • This binding cause the bonds between troponin and tropomyosin to weaken.
    *This causes a conformational change of tropomyosin(roll away) and exposes the myosin-binding site of actin.
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24
Q

What happens in the Cross- bridge attachment stage?

A
  • Myosin(thick) now binds to the active site of actin filaments(thin) forming a Cross-bridge.
    *This starts excitation- contraction coupling (link between generation of AP and start of muscle contraction)
    (excitation-contraction coupling)
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25
Q

True or False? In the myosin-pivoting stage, Myosin heads behind to pivot or cock towards the Z-line pulling the actin filaments closer to the Z-line.

A

FALSE!!! The myosin heads pivots or cock towards the M-LINE pulling the actin filaments closer to the M-LINE.

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26
Q

Fill in the blanks.” As the mysosin heads pivot, the energy stored in them (ATP) is broken down and released as ADP + Pi. This is called a ______”

A

Power stroke

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27
Q

What is the name of the process in which the myosin heads pivot or cock towards the M-Line , pulling the actin filaments closer towards the M-line?

A

Contraction of skeletal muscle

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28
Q

In what stage does the process known as Excitation- Contraction Coupling occur?

A

In the Cross-Bridge attachment stage

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29
Q

In what stage does muscle relaxation happen?

A

The cross-bridge detachment stage

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30
Q

What happens when the skeletal muscle relaxes?

A

❖Ca2+ levels return to normal
❖ Na+ channels close
❖ K+ channels open and the initial resting state of the membrane is restored as K+ leaves the sarcoplasm
❖ The sarcomere returns to its original length

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31
Q

In the muscle relaxant( cross-bridge detachment ) stage , which channels are opened?

A

Potassium channels

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32
Q

In the muscle relaxant stage, which channels are closed?

A

Sodium channels

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33
Q

What happens in the myosin reactivation stage?

A

*When more ATP is split by free myosin heads, reactivation of myosin occurs.
*The process can be repeated as long as there is continued stimulus, and availability of Ca2+ and ATP.

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34
Q

What are different sources of energy that can rephosphorylate ADP back to ATP?

A

1.Phosphocreatine (creatine phosphate):
2. Glycolysis of glycogen previously stored in muscle cells
3. Oxidative (Aerobic) metabolism

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35
Q

In smooth muscle contraction, what is the name of the molecule that calcium binds to?

A

Calmodulin

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36
Q

Fill in the blanks. “ Individual smooth muscle cells are connected via _________”

A

Gap junctions

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37
Q

True or False? Each power stroke increases the length of the sarcomere by ~ 1%.

A

FALSE!!! Each power stoke SHORTENS the length of the sarcomere.

38
Q

Fill in the blanks.” Oxidative metabolism is a _______ metabolism while Creatine phosphate and Glycolysis are _______ metabolisms.”

A

Oxidative - Aerobic ( O - oxygen)
Creatine phosphate and Glycolysis ( Anaerobic)

39
Q

Which source of Energy give max contractions within 5-8 seconds?

A

Creatine Phosphate

40
Q

Which source of Energy give max contractions within hours?

A

Oxidative metabolism

41
Q

Which source of Energy give max contractions within many seconds > 1 min?

A

Glycolysis

42
Q

True or False? Type I fibres are slow- oxidative fibres.

A

TRUE!!

43
Q

True or False? Type II b fibres are fast-oxidative fibres.

A

FALSE . They are fast- glycolitic

44
Q

What type of fibres are Type IIa fibres?

A

Fast-oxidative
“Type II A are oxidAtive”

45
Q

What type of fibres are Type II x fibres?

A

Fast-glycolytic

46
Q

What type of fibres are Type IIb fibres?

A

Fast-glycolytic

47
Q

Fill in the blanks. “ In smooth muscle contraction, When calcium binds to calmodulin, the complex activates _______”

A

Myosin- light chain kinase (MLCK)

48
Q

What is the function of the enzyme Myosin- light chain kinase (MLCK)?

A

It phosphorylates myosin light-chains in myosin heads and increases their myosin ATPase activity.

49
Q

In smooth muscle contraction , which enzyme eventually inhibits contraction by dephosphorylating myosin- light chains.

A

Myosin light-chain phosphatase

50
Q

Where is the Ca2+ source in smooth and cardiac muscle?

A

Mostly from ECF

51
Q

In cardiac muscle , what is the name of the molecule to which Ca2+ binds to?

A

Troponin C

52
Q

How does relaxation occur in cardiac smooth muscle?

A

When Ca+ unbinds from Troponin

53
Q

Fill in the blanks. “In cardiac muscle, influx of Ca2+ via these channels triggers the release of Ca2+ stored in the sarcoplasmic reticulum (ie, Ca2+-induced Ca2+ release) by activating the _______”

A

Ryanodine receptor (RyR)

54
Q

Fill in the blanks.” In skeletal muscle, the voltage-gated __________in the T tubule triggers Ca2+ release from the __________ via the ___________”

A

In skeletal muscle, the voltage-gated DIHYDROPYRIDINE RECEPTOR in the T tubule triggers Ca2+ release from the SARCOPLASMIC RETICULUM (SR) via the RYANODINE RECEPTOR(RyR).

55
Q

True or False? In cardiac muscle , Ca2+ is released by from the sarcoplasmic reticulum via Ryanodine receptors.

( Calcium- induced calcium release)

A

TRUE!!

56
Q

True or False? In skeletal muscle, the dihydropyridine receptors (DHPR) that serves as the voltage sensor triggers release of Ca2+ from the nearby sarcoplasmic reticulum via physical interaction with the RyR.

(dihydropyridine receptor–induced calcium release)

A

TRUE!!

57
Q

What is the name of the protein that is leaked during cardiac myocyte damage, and measurement of it is very sensitive for detecting myocardial infarction?

A

Troponin

58
Q

What is a muscle twitch?

A

A muscle twitch or fasciculation is a small, local, involuntary muscle contraction that is
*Visible under the skin
*Arises from spontaneous discharge of a bundle of skeletal muscle fibres

59
Q

How can a twitch be accomplished by ?

A
  • By electrically stimulating a NERVE
    -Passing a short electrical stimulus through the MUSCLE itself
60
Q

In a single fibre contraction, Contraction-Excitation coupling takes place in what period?

A

Latent (Lag period)

61
Q

In a single fibre contraction,tension rises as cross-bridges swivel & pull actin filaments towards M-line and the sarcomere length shortens in what period?

A

Contraction period

62
Q

How long is the latent(lag) period?

A

delay of ~1-2 ms

63
Q

True or False? In the latent(lag) period, the sarcomere returns to its original length, and there is K+ efflux from the cell.

A

FALSE!! This occurs in the Relaxation Period.

64
Q

What stage of skeletal muscle contraction occurs in the latent period?

A

Actin active- site exposure stage -

*Impulse travels along sarcolemma & down T-tubules to sarcoplasmic reticulum (triads)
*Calcium is released
*Calcium binds binds to troponin Actin active site is exposed
*Myosin binds to actin (cross-bridge formation) = Contraction-Excitation coupling

65
Q

What is Isometric contraction?

A

Involves maintenance of constant MUSCLE LENGTH by a contracted muscle against a load as it is unable to shorten b/c the load is great.

” IsoMETRIC - Metre- Length”

66
Q

What is Isotonic contraction?

A

Involves maintenance of constant MUSCLE TENSION in a contracted muscle against a load due to the muscle’s maximal force of contraction exceeding the total load on the muscle.

” Drinking Tonic (isotonic) makes you Tense
(muscle tension)”

67
Q

Fill in the blank. “In _______, the muscle is unable to shorten.”

A

Isometric Contraction

68
Q

What term is used to describe when a muscle lengthens?

A

Eccentric

69
Q

What term is used to describe when a muscle shortens?

A

Concentric

70
Q

True or False? In isotonic contraction, energy is dissipated as heat rather than through performance.

A

FALSE!! That occurs in isometric contraction

71
Q

Biceps curls, swimming, cycling, running are examples of what type of muscle contraction?

A

Isotonic contraction

72
Q

What are some examples of Isometric contraction?

A

Pushing against a wall
Holding weight in fixed position
Holding a stack of books
Body building pose

73
Q

What is Summation?

A

Adding of individual twitch contractions to increase the intensity of overall muscle contraction.

74
Q

In what ways can Summation occur?

A

1) Multiple fibre ( motor unit or quantal) summation or Recruitment.
2)Frequency (wave or temporal) summation

75
Q

What happens in Multiple fibre summation ( Recruitment) ?

A

Increasing the number of motor units contracting simultaneously.

76
Q

What happens in Frequency summation?

A

Increasing the frequency of contraction

77
Q

What is Tetanus (Tetanic contraction)

A

This happens when rapidly repeated stimulation, leads to an activation of the contractile mechanism which occurs repeatedly before any relaxation has occurred, and the individual responses fuse into one continuous contraction.

78
Q

How do tetany arise?

A

Tetany arises because enough calcium ions are maintained in the muscle sarcoplasm, even between APs, so that full contractile state is sustained without allowing any relaxation between the APs.

79
Q

What are other names for Treppe?

A

Augmentation or The staircase effect/phenomenon

80
Q

What is Treppe?

A

The gradual increase in the strength of muscle contraction to a plateau following rapidly repeated,NON- SUMMATION stimulation after a quiescent period.

81
Q

True or false? In Treppe, Strength of contraction decreases with successive contractions.

A

FALSE!! In tripe , the strength of contraction INCREASES

82
Q

Fill in the blank,” In augmentation the strength of the stimulus __________.”

A

Remains the same

83
Q

What is the cause of the staircase effect ?

A

Increased efficiency of ion gates as they are stimulated repeatedly

84
Q

Fill in the blanks. “ It is a _________when no relaxation occurs between stimuli and an _________ when periods of incomplete relaxation take place between the summated stimuli.

A

Complete tetanus ( no relaxation between stimuli.

Incomplete tetanus ( periods of incomplete relaxation take place between the summated stimuli)

85
Q

What is fatigue?

A

The inability to exert force with one’s muscles to the degree that would be expected, given the individual’s general physical fitness

86
Q

True or False?Accumulation of lactic acid – increases acidity (lowers pH) which can lead to Fatigue.

A

TRUE!!

87
Q

True or False? Fatigue can occur as a result of calcium leaking into muscle cells.

A

TRUE!!

88
Q

Why does muscle hypertrophy occur?

A
  • Results from increase in the number of actin and myosin filaments in each muscle fibres.
    *May arise from muscles being stretched beyond normal length.
    *Few strong contractions each day can cause significant hypertrophy within 6 to 10 weeks
89
Q

What are common causes that lead to muscular atrophy?

A

➢Cancer
➢AIDS
➢ Congestive heart disease
➢ COPD (chronic obstructive pulmonary disease)
➢ Renal failure
➢ Severe burns
➢ Poliomyelitis
➢ Stroke
➢ Starvation

90
Q

What is Rigor mortis?

A

This is a state of contracture of all the muscles of the body several hours after
death (muscles contract and get rigid, even without APs).

Neuroscience (6 decks)

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