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

4 Molecular mechanisms of muscle contraction Flashcards

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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
structure of sarcomere = A-band A for ANISOTROPIC
A for fAt = portion of sarcomere with thick filaments = myosin length (which will overlap with the myosin
26
structure of sarcomere = H-zone
zone of the thick filaments that is not superimposed by the thin filaments = the length of myosin not overlapping the actin
27
structure of sarcomere = Z-line
anchoring part for the actin filaments, marks boundary of individual sarcomere
28
structure of sarcomere = M-line
M for middle (in middle of myosin)
29
titin
aka connectin = giant protein which extends from Z line to myosin
30
actin
= thin filaments, are the major component of the I-band and extend into the A-band
31
myosin
= thick filaments, are bipolar and extend throughout the A-band, cross-linked at the centre by the M-band
32
myosin structure
2 heavy chains 2 light chains has length and heads which bind to the actin
33
troponin
protein to which ca++ binds to | changes shape and moves tropomyosin
34
tropomyosin
blocks binding sites on actin when bound, is moved out of the way by troponin when ca2+ binds to troponin
35
AP arrives at NMJ...
ca++ released from sarcoplasmic reticulum (SR) which then goes to bind to troponin
36
attachment of myosin to actin
myosin head with ADP + Pi
37
power stroke
myosin head bends, pulling along the actin filament, ADP + Pi are released
38
stage 1 of the cross-bridge theory
DETACHMENT ATP bind to myosin head
39
stage 2 of the cross-bridge theory
HYDROLYSIS of ATP myosin head attached to ADP + Pi ready to bind to actin
40
stage 3 of the cross-bridge theory
CROSS-BRIDGE myosin head binds to the actin with ADP + Pi still attached
41
stage 4 of the cross-bridge theory
POWER STROKE release of the ADP + Pi causes myosin head to move and so move the thin filament
42
does A band change length
no! | A band stays the sAme
43
Isotonic contraction
cause muscle to change length as it contracts and thus move
44
Isometric contraction
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
concentric contraction
muscle shortens as it contracts - occur frequently in daily and sporting activities
46
eccentric contraction
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
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
mechanical response of an individual muscle fibre, an individual motor unit, or a whole muscle to a single AP
48
muscle contraction is based on the twitch of a fibre similar to an AP because
a twitch is an all or nothing event
49
phases of the twitch
1. latent 2. contraction 3. relaxation
50
latent phase of the Twitch
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
contraction phase of the Twitch
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
relaxation phase of the Twitch
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
Type I muscle fibre
= 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
Type II a muscle fibre
= 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
Type II b muscle fibre
= 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
Type II b muscle fibre
= 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
muscle disorders
- Injury or overuse – strain, sprain, cramps, tendinitis - Genetic disorder – muscular dystrophy - Inflammation – myositis, polymyalgia rheumatic - Parkinson’s disease, Myasthenia gravis, Multiple sclerosis
58
Force of Muscle Contraction depends on...
- Number of action potentials per second - Number of motor units recruited - Amount of overlap between thick & thin filaments
59
Optimum muscle length = greatest force of contraction
number of active cross bridges is the greatest = actin and myosin overlap fully
60
muscle becomes shorter than the optimum length = decreasing length of sarcomere
- 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
muscle becomes longer than the optimum length = increasing length of sarcomere
number of active cross bridges decreases because the overlap between the actin and myosin fibres decrease = tension reduces
62
incomplete/ unfused tetanus
tension can oscillate around an average level
63
complete/ fused tetanus
maximum number of crossbridges to cycle = at this point the tension plateau smoothes out
64
maximum tetanic tension
when the muscle is at maximum sustained tension
65
summation of APs cause increase in levels of ca2+ as not all is taken back into SR before it is released again
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
larger motor units are required
to generate larger forces

IMS Nerves and muscles (5 decks)

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