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BIOSCI 107 > L4 - Muscle > Flashcards

L4 - Muscle Flashcards

1
Q

Built-in heart rhythm

A

Autorhythmicity - regulated through a system of pacemakers

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2
Q

Muscle tissue composition

A

Elongated cells: muscle cells/muscle fibres/myocytes

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3
Q

Muscle tissue mechanism

A

Use energy from hydrolysis of ATP to generate force

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4
Q

ATP

A

Adenosine triphosphate

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5
Q

Muscle tissue function

A
  • produce body movements
  • maintain posture (stabilising body positions)
  • generate heat
  • protection
  • storing/moving substances within body (peristalsis - smooth muscles, pump blood - cardiac muscles)
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6
Q

Types of muscle tissue

A

Skeletal, cardiac, smooth

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7
Q

Skleteal muscle features

A

~650 named skeletal muscles in body

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8
Q

Skeletal muscle control

A

voluntary (contraction is under conscious control but doesn’t always require conscious control - e.g posture)

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9
Q

Skeletal muscle location

A

Attached to bones by tendons

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10
Q

Skeletal muscle function

A

motion, posture, heat, protection

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11
Q

Skeletal muscle examples

A

Stapedius, sartorius

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12
Q

Stapedius features

A
  • smallest at 1.25 mm
  • stabilises smallest human bone (stapes) in the ear
  • changes tension (muscle tightens) to control sensitivity of hearing by altering the amount of sound vibration transmitted through eardrum
  • supplied by a small branch of facial nerve
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13
Q

Bell’s Palsy

A

paralysis of nerve causes changes in facial appearance and hyperacusis (extra loud sound perception)

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14
Q

Sartorius features

A
  • longest at up to 60 cm
  • in the thigh and in charge of twisting to be able to see the bottom of feet
  • hip: flexor, abductor, lateral rotator
  • knee: flexor
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15
Q

Skeletal muscle structure

A
  • Striated (alternating light and dark bands within fibres under microscope)
  • relatively big, long, cylindrical, ordered cells/fibres
  • Multinucleate with many peripheral nuclei pushed to the side
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16
Q

Connective tissue in muscle

A

Epimysium, perimysium, endomysium, tendons

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17
Q

Epimysium location

A

surrounds anatomical muscle (very outer layer - fibrous fascia)

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18
Q

Epimysium composition

A

dense irregular connective tissue

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19
Q

Epimysium function

A

stops muscles from sticking to other muscle

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20
Q

Perimysium location

A

around fascicles

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21
Q

Fasicles

A

a bundle of cells grouped together which can move as individual units

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22
Q

Perimysium composition

A

dense irregular connective tissue

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23
Q

Endomysium location

A
  • around muscle fibres/cell

- sits outside the sarcolemma

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24
Q

Endomysium composition

A

Areolar connective tissue - mostly reticular fibres

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25
Q

Endomysium function

A
  • penetrates interior of each fascicle and separates individual muscle fibres from one another
  • layer for capillaries and nerves (needed due to voluntary control)
  • generally, one artery and one or two veins accompany each nerve that penetrates a skeletal muscle
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26
Q

Tendons and aponeuroses formation

A

The three connective tissue layers (epimysium, perimysium, endomysium) extend beyond to form tendons (rope like) and aponeuroses (broad, flat sheet)

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27
Q

Muscle cell structural components

A

Sarcolemma, sarcoplasm, transverse (T) tubules

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28
Q

Sarcolemma

A

Actual cell plasma membrane

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29
Q

Sarcoplasm

A

Cell cytoplasm

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30
Q

Sarcoplasm composition

A

glycogen and myoglobin (red protein that binds oxygen molecules and releases them when needed)

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31
Q

Transverse (T) tubules

A
  • tiny invaginations of sarcolemma
  • tunnel in from surface towards centre of each muscle fibre
  • filled with interstitial fluid as they are open to the outside of the fibre
  • muscle action potentials travel along sarcolemma and through T tubules (quickly spreading throughout muscle fibre = all parts of muscle excited at same instant)
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32
Q

Sarcoplasmic reticulum

A
  • fluid-filled system of membranous sacs
  • encircles each myofibril
  • relaxed form: stores calcium ions where release of these ions tiggers muscle contraction
33
Q

Myofibrils features

A
  • 2µm in diameter
  • the contractile units of muscle fibres
  • highly organised arrangement of myofibrils within cells cause striations
  • more or less fill the sarcoplasm
  • extends the muscle fibre’s entire length
    (- the tubular structure made of sarcomeres)
34
Q

Myofibrils composition

A

Myofilaments (, proteins)

35
Q

Protein types in myofibrils

A

Contractile, regulatory, structural

36
Q

Contractile protein function

A

Generate force during contractions

37
Q

Contractile protein examples

A

Myosin, actin

38
Q

Regulatory proteins function

A

Help switch contraction process on and off

39
Q

Structural protein function

A
  • keep thick and thin filaments in proper alignment
  • give myofibril elasticity and extensibility
  • link myofibrils to sarcolemma and ECM
40
Q

Myofilament feature

A

do not extend the length of the muscle fibre (arranged in compartments - sacromeres)

41
Q

Types of myofilaments

A

Thin filament, thick filament

42
Q

Thick filament size

A
  • twice the thin filaments: 16 nm diam

- 1-2 µm long

43
Q

Thick filament composition

A

Myosin protein

44
Q

Thin filament size

A
  • 8 nm diam

- 1-2 µm long

45
Q

Thin filament composition

A

Mostly actin protein

46
Q

Sarcomere features

A
  • basic functional unit of myofibril

- coordinated but independent contractions

47
Q

Sarcomere components

A

A band, I band, H zone, M line, Z discs, Titin filaments, Zone of overlap

48
Q

A band

A
  • dark (due to thick filaments), middle of sarcomere

- contains all thick filaments (including overlap)

49
Q

I band

A
  • lighter, less dense area
  • ONLY thin filaments and NO thick filaments (spans between end of one thick filament to another - doesn’t include overlap zone)
  • one Z disc passes through centre of each I band
50
Q

H zone

A
  • narrow region in centre of each A band

- ONLY thick filaments and NO thin filaments (spans between ends of overlap zones)

51
Q

Zone of overlap

A
  • where thin and thick filaments overlap (to different degrees depending on state of contraction)
  • 2 thin filaments for every thick filament
52
Q

M line

A
  • middle of sarcomere/H zone

- contains protein discs that orientate/line up and hold thick filaments together

53
Q

Z discs

A
  • narrow, plate-shaped regions of dense material
  • passes through centre of I band
  • located between sarcomeres: separates and defines sarcomere units
  • made of actinin proteins that link filaments of adjacent sarcomeres (thin filaments are anchored to Z discs)
54
Q

Titin filament

A
  • links Z disk to M line

- provides resisting tension on I band (like a molecular spring)

55
Q

Cardiac muscle control

A

Involuntary

56
Q

Cardiac muscle location

A

Heart wall

57
Q

Cardiac muscle function

A

Pumps blood to all parts of body

58
Q

Cardiac muscle structure

A
  • Striated fibres (like skeletal): sarcomere structure
  • Branched
  • Single central nucleus (occasionally two)
  • Fibres join end-to-end through intercalated discs
59
Q

Intercalated discs function

A
  • allows coordinated activity by linking different muscles together to result in walls contracting in an ordered way when pumping blood
60
Q

Intercalated discs junctions

A

Desmosomes, gap junctions

61
Q

Desmosomes in intercalated discs

A
  • bind intermediate filaments
  • provide adhesion (hold fibres together) in contraction
  • strengthen, structure
62
Q

Gap junctions in intercalated discs

A
  • communication (electrical signals)

- coordinated, rapid conduction

63
Q

Smooth muscle control

A

Involuntary

64
Q

Smooth muscle location

A
  • walls of hollow internal structures
  • structures where diameter size needs to change (intestines - peristalsis, blood vessel walls - constriction, iris of eye, reproductive - uterus. digestive - gallbladder/respiratory - airways to Lungs/urinary - bladder, skin erector pili - Controls direction of hair, stomach)
65
Q

Smooth muscle function

A
  • motion (constriction of blood vessels, airways, propulsion of foods through gastrointestinal tract, contraction of urinary bladder/gallbladder)
66
Q

Smooth muscle structure

A
  • non-striated (smooth)
  • short, small, spindle-shaped (about 30-200 µm long, 3-8 µm thickest in middle)
  • single, central nucleus
  • bundles of thin and thick filaments in unordered way
67
Q

Smooth muscle shape advantage

A
  • conducive to going around circular/hollow organs as they can pack easily together which results in a more efficient contractile process when changing the diameter of the inner lumen (inside space of tubular structures)
68
Q

Thin filaments in smooth muscle

A

Attach to dense bodies

69
Q

Dense bodies

A

Major protein actinin

- functionally similar to Z discs as contractile apparatus spans between dense bodies)

70
Q

Intermediate filaments in smooth muscles

A

Also connect dense bodies

- non-contractile elements (rigid rods)

71
Q

Intermediate filament function in smooth muscles

A

During contraction, tension is transmitted to the intermediate filaments and the cell widens/twists about these stable rods as it contracts/squishes

72
Q

Junctions in smooth muscle

A

Gap junctions

73
Q

Gap junctions in smooth muscle

A

Connect many individual fibres

74
Q

Smooth muscle cells with gap junctions

A

Powerful contractions due to fibres contracting in unison

E.g gut

75
Q

Smooth muscle cells without gap junctions

A

Individual contraction like skeletal muscles

E.g iris of eye

76
Q

Tendon composition

A

Dense regular tissue

77
Q

Tendon function

A

Attaches to bone

78
Q

Tendon example

A

Achilles (calcaneal) tendon

79
Q

Intercalated discs

A

transfer thickenings of plasma membrane unique to cardiac muscle

BIOSCI 107 (15 decks)

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