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Biology > BIOSCI 107 ET: Muscle > Flashcards

BIOSCI 107 ET: Muscle Flashcards

1
Q

What are the 3 Types of Muscle?

A

Skeletal, cardiac, smooth.

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2
Q

Which Muscle Types are Striated?

A

Skeletal and cardiac.

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3
Q

Which Muscle Types are Under Voluntary Control?

A

Skeletal.

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4
Q

Where is Cardiac Muscle Located?

A

Heart.

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5
Q

Where is Smooth Muscle Located?

A

Wall of internal organs.

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6
Q

How can we Identify Skeletal Muscle Cells?

A

Sing long cylindrical cells, multiple peripheral nuclei.

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7
Q

How can we Identify Cardiac Muscle Cells?

A

Branched cells connected via intercalated discs.

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8
Q

How can we Identify Smooth Muscle Cells?

A

Spindle shaped, with a single nucleus.

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9
Q

What are Skeletal Muscle Cells Composed of?

A

Fibrils containing contractile filaments.

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10
Q

Where are Thick Filaments Found?

A

Running the entire length of an A Band.

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11
Q

Where are Thin Filaments Found?

A

Running the length of the I Band and partway into the A Band.

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12
Q

What is a Z Disc?

A

Coin-shaped sheet of proteins that anchors the thin filaments and connects myofibrils to one another.

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13
Q

What is the H-Zone?

A

Lighter mid-region where filaments do not overlap.

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14
Q

What is the M Line?

A

Line of protein myomesin that holds adjacent thick filaments together.

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15
Q

What is the Function of a T-Tubule?

A

Allows action potentials to be carried deep within the muscle cell.

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16
Q

What is a T-Tubule?

A

Deep invagination continuous with the sarcolemma, circling each sarcomere at the junctions of A and I Bands.

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17
Q

What is the Sarcoplasma Reticulum?

A

Calcium storage site.

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18
Q

What are Thick Filaments Composed of?

A

Myosin.

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19
Q

What is the Structure of Myosin in Thick Filaments?

A

2 subunits, each has a globular head and a tail, 2 tails intertwine to form a helix.

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20
Q

What is Located in the Globular Heads of Myosin?

A

A binding site for actin - the head itself is an enzyme that hydrolyses ATP.

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21
Q

What is the Function of Titin in Myosin?

A

Anchors the thick filament to the Z-line.

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22
Q

What is the Thin Filament Composed of?

A

Globular actin proteins.

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23
Q

What is the Structure of the Thin Filament?

A

Double stranded helical actin chain (polymers).

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24
Q

What are Troponin and Tropomyosin?

A

Regulatory proteins associated with actin.

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25
Q

What is the Sliding Filament Theory of Muscle Contraction?

A

Sarcomere shortens as thin filaments are pulled over thick filaments - Z line pulled towards M line, I band/H zone become narrower.

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26
Q

Describe the 4 Stages of the Cross Bridge Cycle.

A

Cross-bridge formation, power stroke, detachment, energization of myosin head.

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27
Q

What are the Requirements for a Cross-Bridge to Form?

A

Calcium must be present, myosin binding site must be exposed.

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28
Q

What Occurs During Stage 1: Cross-Bridge Formation?

A

Myosin binds to the actin binding site to form a cross-bridge.

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29
Q

What Occurs During Stage 2: The Power Stroke?

A

ADP released, myosin head rotates to low energy state, taking thin filament with it, sarcomere is shortened.

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30
Q

What Occurs During Stage 3: Detachment?

A

New ATP molecule binds to myosin, actin-myosin bind is weakened and myosin detaches.

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31
Q

What Occurs During Stage 4: Energization of Myosin Head?

A

Myosin head hydrolyses ATP to ADP + Pi, head moves to high energy (cocked) state.

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32
Q

What is the Critical Threshold for Calcium in the Cross-Bridge Cycle?

A

0.001 - 0.01 mM.

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33
Q

Why is Calcium Important in the Cross-Bridge Cycle?

A

Calcium ions provide on switch - binding to troponin so tropomyosin exposes myosin binding sites on actin.

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34
Q

How is Calcium Regulated for the Cross-Bridge Cycle?

A

Calcium channels and active pumps move Ca from cytoplasm back into sarcoplasma reticulum.

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35
Q

What is Isotonic Muscle Activity?

A

Shortening/lengthening, tension constant, velocity variable.

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36
Q

What is Isometric Muscle Activity?

A

No shortening, length constant, tension variable.

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37
Q

What Happens during an Isometric Contraction?

A

At sarcomere level max active force is dependent on the degree of actin and myosin overlap.

38
Q

What Happens to Active Tension at Lengths <2.0 uM?

A

Filaments collide and interfere with each other, reducing force developed.

39
Q

What Happens to Active Tension at Lengths >2.2 uM?

A

Active forces decline as the extent of overlap between filaments reduce, reducing number of cross bridge.

40
Q

What is Total Tension?

A

Active + passive force.

41
Q

What Happens to Connective Tissue when Muscle is Stretched?

A

Connective tissue around the muscle cells resists the stretch = passive force.

42
Q

What is a Motor Unit?

A

A motor neuron and all the muscle fibres it innervates.

43
Q

What Happens when ACh is Released into the Neuromuscular Junction?

A

Action potential travels down motor neuron, Ca channels open, Ca enters axon terminal, ACh vesicles fuse with membrane, ACh released into synpatic cleft.

44
Q

What Happens when ACh Receptors are Activated?

A

Binding of ACh to receptors causes opening of ACh gated ion channels, this allows movement of mostly Na into muscle cell - making it less positive.

45
Q

What Happens when a Muscle Action Potential is Triggered?

A

Ligand gated channels enable end plate potential to reach threshold, voltage gated Na channels open triggering action potential, this is propagated along sarcolemma.

46
Q

What Happens when Calcium is Released from the SR?

A

Action potential is conducted down t tubules, results in voltage gated Ca channels, Ca is released into cytosol.

47
Q

What Happens when Ca Binds with Troponin?

A

Ca concentrations reach threshold, myosin binding sites are exposed, cross bridge cycle occurs.

48
Q

What Happens when the Contraction Ends due to Fallen Ca Levels?

A

Ca actively pumped into sarcoplasmic reticulum, troponin moves back covering myosin binding sites.

49
Q

How long can Creatine Phosphate act as an ATP Store?

A

Less than 15 seconds.

50
Q

What does Creatine + ADP Make?

A

Creatine + ATP.

51
Q

Why is Anaerobic Glycolysis Limited to 30-40s?

A

Build up of lactic acid and protons.

52
Q

What is Regulation of Force Dependent on?

A

Rate of stimulation of individual motor units, number of motor units recruited.

53
Q

What is a Type 1 Motor Unit?

A

Slow twitch - units with neurons innervating the slow efficient aerobic cells.

54
Q

What is a Type 2 Motor Unit?

A

Fast switch - units with the neurons innervating the large fibres that fatigue rapidly but develop large forces.

55
Q

What is the ‘Glue’ Preventing Cells from Separating During Contraction?

A

Desmosomes.

56
Q

What is a Major Function of Gap Junctions in Cardiac Muscle Cells?

A

Allow action potentials to be carried from one cell to the next.

57
Q

How Long does a Ventricular Myocyte Action Potential Last?

A

Long - >100ms.

58
Q

Why is there a Plateau Phase for the Ventricular Myocyte Action Potential?

A

Due to presence of a large sustained Ca ion current.

59
Q

What are the 3 Major Stages of an Action Potential in a Cardiac Muscle Cell?

A

Rapid depolarisation, plateau, repolarisation.

60
Q

Why is there Rapid Depolarisation in the Action Potential of a Cardiac Muscle Cell?

A

Due to fast voltage-gated Na channel.

61
Q

Why is there Repolarisation in the Action Potential of a Cardiac Muscle Cell?

A

Closing of Ca channels and opening of K channels.

62
Q

What are the 4 Pathways Ca can Utilise to Exit the Cytosol?

A

SR Ca-ATPase, sarcolemmal Na/Ca exchange, sarcolemmal Ca-ATPase, mitochondrial Ca uniport.

63
Q

What does a Longer Action Potential For Cardiac Muscle Mean?

A

Longer contractile phase.

64
Q

How is Cardiac Output (CO) Calculated?

A

CO = SV x HR

Stroke volume x heart rate

65
Q

What is Stroke Volume?

A

The tension developed by the cardiac muscle fibres in one contraction.

66
Q

What are the 3 Methods of Increasing Stroke Volume?

A

Increased stretch of ventricles/rate of firing, certain neurotransmitters.

67
Q

Which Node Determines the Heart Rate?

A

SA node in right atrium.

68
Q

What are the 3 Stages of the Action Potential for Pacemaker Cells?

A

Pacemaker potential, depolarisation, repolarisation.

69
Q

Why does the Pacemaker Potential show a Slow Depolarisation?

A

Due to If current.

70
Q

Why does is there Depolarisation for the Action Potential of Pacemaker Cells?

A

At threshold Ca channels open, influx is sustained by slow opening Ca channels.

71
Q

Why does is there Repolarisation for the Action Potential of Pacemaker Cells?

A

Ca channels inactivate and K channels open.

72
Q

What is the Function of the Vagus Nerve?

A

Decreases heart rate, releases ACh.

73
Q

What is the Function of Sympathetic Cardiac Nerves?

A

Increase heart rate and force of contraction.

74
Q

What is Starlings Law of the Heart?

A

AS the resting ventricular volume is increased the force of the contraction is increased.

75
Q

What is the Length Tension Relationship for Cardiac Muscle?

A

Increased stretch results in more force developed (stroke volume).

76
Q

What is the Concept of Automaticity?

A

Increasing heart rate increases contractile force - less time for Ca to be pumped out.

77
Q

What is Inotropy?

A

More force developed per given length.

78
Q

How does Noradrenaline Impact Stroke Volume?

A

Increased cytosol calcium, increased HR shortening time for extrusion.

79
Q

What is Multiunitary Organisation in Smooth Muscle?

A

Bundles of cells which contract independently.

80
Q

What is Unitary/Visceral Organisation in Smooth Muscle?

A

Sheets of electrically coupled cells that act in unison.

81
Q

Do Smooth Muscle Cells have T-Tubules?

A

No - caveolae instead (increase SA).

82
Q

How is Actin Anchored to the Sarcolemma in Smooth Muscle Cells?

A

Dense bodies act like z-lines.

83
Q

What is the Function of Gap Junctions in Smooth Muscle?

A

Electrically connect cells together (unitary).

84
Q

What are Intermediate Filaments in Smooth Muscle Cells?

A

The cytoskeletal element.

85
Q

What is the Regulatory Protein of Smooth Muscle Cells?

A

Calmodulin.

86
Q

What Impact does the Disorganisation of Smooth Muscle Have?

A

Greater shortening.

87
Q

What is the Only Important Part of Initiation of Contraction in Smooth Muscle?

A

Can be neural, hormonal or spontaneous.

88
Q

What is the Function of Myosin Light Chain Kinase?

A

Phosphorylates the light chain in the presence of activated calmodulin.

89
Q

How is Smooth Muscle Relaxed?

A

When a myosin light chain phosphatase dephosphoralates the myosin light chain.

90
Q

What is the Function of Autonomic Nerve Fibres?

A

Innervate most smooth muscle fibres.

91
Q

What is the Function of Varicosities?

A

Release neurotransmitters into a wide synaptic cleft.

92
Q

What is the Stretch-Relaxation Response of Smooth Muscle?

A

Initial contraction (resisting stretch), slowly relax (adapting to change in length).

Biology (15 decks)

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