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IMS Nerves and muscles > 4 Molecular mechanisms of muscle contraction > Flashcards

4 Molecular mechanisms of muscle contraction Flashcards

1
Q

pennate muscle

A

feathered fascicles arrangement (fibre bundles): uni/bi/multipennate

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2
Q

fusiform muscle

A

spindle shaped, tapered at both ends with circular cross section, parallel fibres

tendon - muscle - tendon

= bicep

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3
Q

parallel muscle

A

fascicles lie parallel to long axis of muscle (often have aponeurosis)

= rectus abdominus (abs) is 2 parallel muscles with linea alba in between

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4
Q

convergent muscle

A

broad attachment from which fascicles converge to a single tendon

= pectoralis major

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5
Q

circular muscle

A

surround a body opening or orifice, constricting it when contracted

= oesophagus

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6
Q

aponuerosis =

A

a sheet of pearly white fibrous tissue that takes the place of a tendon in flat muscles having a wide area of attachment

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7
Q

tendon vs ligament

A

tendon = muscle to bone

ligament = bone to bone

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8
Q

three types of muscle

A
  1. skeletal
  2. cardiac
  3. smooth
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9
Q

skeletal muscle

A

striated, multinucleated, voluntary, non-branching, attached to skeleton

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10
Q

cardiac muscle

A

striated, single nucleus, involuntary, branched, heart muscle

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11
Q

smooth muscle

A

non-striated, single nucleus, involuntary, tapered, forms walls of organs

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12
Q

what does striated mean

A

tissue that features repeating functional units called sarcomeres = striped appearance

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13
Q

attaching bone to muscle =

A

tendon

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14
Q

muscle belly structure: Epimysium

A

sheath of fibrous elastic tissue surrounding an entire muscle

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15
Q

muscle belly structure: Perimysium

A

sheath of connective tissue surrounding a fascicle

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16
Q

muscle belly structure: Endomysium

A

surrounds individual muscle fibres / between fibres

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17
Q

muscle belly structure: fascicle

A

contain numerous muscle cells which each contain hundred to thousands of myofibrils (chains of thousands of sarcomeres)

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18
Q

muscle belly structure: sarcolemma

A

the plasma membrane of the individual muscle cell or muscle fibre
within sarcolemma = sarcoplasm, sarcoplasmic reticulum and myofibrils

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19
Q

muscle belly structure: myofibril

A

thousands of myofibrils in every muscle cell

contain actin and myosin filaments

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20
Q

list structures of muscle belly macroscopic -> microscopic

A

epimysium - perimysium - fasicle - endomysium - sarcolemma - muscle fibre - myofibril - sarcomere

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21
Q

myocyte

A

muscle cell or muscle fibre (same thing)

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22
Q

basic definition of sarcomere

A

smallest contractile unit of striated muscle

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23
Q

sarcomere boundaries

A

segment between two neighbouring Z-lines

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24
Q

structure of sarcomere = I-band

I for ISOTROPIC

A

I for thIn

= portion of sarcomere with thin filaments
= actIn or acTHIN

not superimposed with thick filaments

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25
Q

structure of sarcomere = A-band

A for ANISOTROPIC

A

A for fAt

= portion of sarcomere with thick filaments
= myosin length (which will overlap with the myosin

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26
Q

structure of sarcomere = H-zone

A

zone of the thick filaments that is not superimposed by the thin filaments

= the length of myosin not overlapping the actin

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27
Q

structure of sarcomere = Z-line

A

anchoring part for the actin filaments, marks boundary of individual sarcomere

28
Q

structure of sarcomere = M-line

A

M for middle (in middle of myosin)

29
Q

titin

A

aka connectin

= giant protein which extends from Z line to myosin

30
Q

actin

A

= thin filaments, are the major component of the I-band and extend into the A-band

31
Q

myosin

A

= thick filaments, are bipolar and extend throughout the A-band, cross-linked at the centre by the M-band

32
Q

myosin structure

A

2 heavy chains
2 light chains

has length and heads which bind to the actin

33
Q

troponin

A

protein to which ca++ binds to

changes shape and moves tropomyosin

34
Q

tropomyosin

A

blocks binding sites on actin when bound, is moved out of the way by troponin when ca2+ binds to troponin

35
Q

AP arrives at NMJ…

A

ca++ released from sarcoplasmic reticulum (SR) which then goes to bind to troponin

36
Q

attachment of myosin to actin

A

myosin head with ADP + Pi

37
Q

power stroke

A

myosin head bends, pulling along the actin filament, ADP + Pi are released

38
Q

stage 1 of the cross-bridge theory

A

DETACHMENT

ATP bind to myosin head

39
Q

stage 2 of the cross-bridge theory

A

HYDROLYSIS of ATP

myosin head attached to ADP + Pi
ready to bind to actin

40
Q

stage 3 of the cross-bridge theory

A

CROSS-BRIDGE

myosin head binds to the actin with ADP + Pi still attached

41
Q

stage 4 of the cross-bridge theory

A

POWER STROKE

release of the ADP + Pi causes myosin head to move and so move the thin filament

42
Q

does A band change length

A

no!

A band stays the sAme

43
Q

Isotonic contraction

A

cause muscle to change length as it contracts and thus move

44
Q

Isometric contraction

A

occurs when no change in length of contracting muscle

= carrying an object in front of you as the weight of the object is pulling your arms down but your muscles are contracting to hold the object at the same level

45
Q

concentric contraction

A

muscle shortens as it contracts - occur frequently in daily and sporting activities

46
Q

eccentric contraction

A

muscle lengthens as it contracts - less common - usually involves control or deceleration of a movement being initiated by the eccentric muscles agonist

This type of contraction puts lots of strain through muscle - commonly involved in muscle injuries

47
Q

twitch definition

muscle contraction is based on the twitch of a fibre similar to an AP because a twitch is an all or nothing event

A

mechanical response of an individual muscle fibre, an individual motor unit, or a whole muscle to a single AP

48
Q

muscle contraction is based on the twitch of a fibre similar to an AP because

A

a twitch is an all or nothing event

49
Q

phases of the twitch

A
  1. latent
  2. contraction
  3. relaxation
50
Q

latent phase of the Twitch

A

the delay of a few milliseconds between an action potential and the start of a contraction and reflects the time for excitation-contraction coupling

51
Q

contraction phase of the Twitch

A

Contraction phase starts at the end of the latent period and ends when the muscle tension peaks (tension = force expressed in grams)

during this time cytosolic calcium levels are increasing as released calcium exceeds uptake

52
Q

relaxation phase of the Twitch

A

Relaxation phase is the time between peak tension and the end of the contraction when the tension returns to zero

during this time cytosolic calcium is decreasing as reuptake exceeds release

53
Q

Type I muscle fibre

A

= SLOW TWITCH

Red in color due to high concentrations of myoglobin
Very resistant to fatigue
Contains large amounts of mitochondria
Contracts slowly
Produces a low amount of power when contracted
Used in aerobic activities such as long distance running

54
Q

Type II a muscle fibre

A

= FAST TWITCH A
Red in color due to high concentrations of myoglobin
Resistant to fatigue (but not as much as Type I fibers)
Contains large amounts of mitochondria
Contracts relatively quickly
Produces a moderate amount of power when contracted
Used in long-term anaerobic activities such as swimming (activities lasting less than 30 minutes)

55
Q

Type II b muscle fibre

A

= FAST TWITCH B

White in color due to low myoglobin concentrations
Fatigue very easily
Contains low amounts of mitochondria
Contracts very quickly
Produces a high amount of power when contracted
Used in short-term anaerobic activities such as sprinting and lifting heavy weights (activities lasting less than a minute)

56
Q

Type II b muscle fibre

A

= FAST TWITCH B

White in color due to low myoglobin concentrations
Fatigue very easily
Contains low amounts of mitochondria
Contracts very quickly
Produces a high amount of power when contracted
Used in short-term anaerobic activities such as sprinting and lifting heavy weights (activities lasting less than a minute)

57
Q

muscle disorders

A
  • Injury or overuse – strain, sprain, cramps,
    tendinitis
  • Genetic disorder – muscular dystrophy
  • Inflammation – myositis, polymyalgia rheumatic
  • Parkinson’s disease, Myasthenia gravis, Multiple
    sclerosis
58
Q

Force of Muscle Contraction depends on…

A
  • Number of action potentials per second
  • Number of motor units recruited
  • Amount of overlap between thick & thin filaments
59
Q

Optimum muscle length = greatest force of contraction

A

number of active cross bridges is the greatest

= actin and myosin overlap fully

60
Q

muscle becomes shorter than the optimum length = decreasing length of sarcomere

A
  • first the thin filaments at opposite ends of the sarcomere first begin to overlap one another and interfere with each other’s movements
  • even shorter then the thick filaments come into contact with the Z lines

= tension reduces

61
Q

muscle becomes longer than the optimum length = increasing length of sarcomere

A

number of active cross bridges decreases because the overlap between the actin and myosin fibres decrease

= tension reduces

62
Q

incomplete/ unfused tetanus

A

tension can oscillate around an average level

63
Q

complete/ fused tetanus

A

maximum number of crossbridges to cycle = at this point the tension plateau smoothes out

64
Q

maximum tetanic tension

A

when the muscle is at maximum sustained tension

65
Q

summation of APs cause increase in levels of ca2+ as not all is taken back into SR before it is released again

A

when the freq of stimulation is so high that Ca2+ levels rise to peak levels, summation results in the level of tension reaching a plateau called tetanus

66
Q

larger motor units are required

A

to generate larger forces

IMS Nerves and muscles (5 decks)

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