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year 2 sem 2 motor systems > muscles > Flashcards

muscles Flashcards

1
Q

smooth muscle length, nucleus, appearance, location and control

A

-30- 200um
-mono-nucleated, central
-spindle shaped, tapered ends, non-striated
-lining tracts: respiratory, cardiovascular, digestive, reproductive
-involuntary (autonomic)

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2
Q

cardiac smooth muscle length, nucleus, appearance, location and control

A

-50-100um
-mono-nucleated mainly (<5)
-branched, striated
-lining of the heart
-self contractable, involuntary (autonomic NS)

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3
Q

skeletal muscle length, nucleus, appearance, location and control

A

-up to 0.3m
-multi nucleated (>100s)
-elongated, striated
-muscles, attached to skeleton
-voluntary (somatic NS)

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4
Q

flexors

A

close angle between limb and body

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5
Q

extensors

A

increase angle between limb and body

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6
Q

abductor

A

movement of limb away from body

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7
Q

adductor

A

movement of limb towards body

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8
Q

prime mover

A

main muscle

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9
Q

antagonists

A

muscles working in opposite directions

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10
Q

fixators/ fixator muscles

A

stabilise

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11
Q

components of skeletal muscle (basic organisation)

A

muscle–> fascicles –>fibres

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12
Q

what makes up a muscle fibre

A

a bundle of filaments

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13
Q

myofibril

A

a muscle fibre (single cell)
elongated rod like shapes

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14
Q

sarcomere

A

smallest contractile unit in a muscle fibre
interdigitated thick and thin filaments, bounded by z discs

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15
Q

how many sarcomeres does each myofibril contain?

A

20,000 sarcomeres in a series

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16
Q

thin filament projection

A

project from z line towards the middle

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17
Q

thick filament projection

A

connected in the middle of the sarcomere, project towards the z lines

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18
Q

M line

A

The line at the centre of a sarcomere to which myosin bind

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19
Q

what is each thin filament composed of?

A

a F actin arranges as a helix plus tropomyosin and troponin

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20
Q

composition of thick filament

A

is made up of about 250 myosin molecules: myosin molecules have globular head

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21
Q

connectins

A

protein

fine, thin, elastic filaments connecting ends of tick filaments and Z-dicks

give muscle its springlike property (this springlike property is important for contraction)

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22
Q

myosin

A

thick filament

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23
Q

actin

A

thin filaments

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24
Q

contractile proteins

A

actin and myosin

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25
what is contractile force caused by
produced by molecular cross bridges between thick and thin filaments
26
what block the binding sites on actin
troponin-tropomyosin complexes on thin filaments block the binding sites on the actin
27
what are myosin heads bound by at rest? what does this mean?
ADP-bound ready to move, but dont have the energy yet
28
what position are myosin heads in at rest?
cocked position
29
calcium in sarcoplasm at rest
low (~ 10^-7 - 10^-8 M) because there is no action potential
30
cross bridges at rest
no cross-brides between thick and thin filaments
31
activation in sarcomere
muscle fibre is activated (action potential travels down T-tubules) Calcium is released from the cisternae of the sarcoplasmic reticulum (SPR) calcium binds to troponin conformational changes in tin filament exposes actin binding sites attachment of cocked myosin heads = cross-bridge formation
32
sarcomere sliding of filaments
Upon formation of cross-bridges, mechanical energy (from ATP dephosphorylation) stored in “cocked” myosin heads is released - POWER STROKE - moves the filament Myosin heads have shed bound ADP: resume relaxed / native state while remaining cross-linked to thin strand Longitudinal force pulls the thin and thick filaments into greater overlap (~0.06 µm) -shortens the muscle fibre (sarcomere) .
33
myosin detachment
ATP binds to Myosin heads which then detaches from its actin binding site Actin-binding site is released and can form another cross-bridge to sustain muscle contraction
34
reactivation of myosin (sarcomere)
Thick filament: Energy released by dephosphorylation of ATP to bound ADP is stored in myosin heads - myosin heads are “re-cocked” Thin filament: High [Ca2+]: system remains activated (step 2), muscle contraction persists. Low [Ca2+ ]: return to resting state (step 1): myosin heads are cocked but unable to form cross-bridge.
35
what do muscle fibres contain
a network of longitudinal tubules and chamber (sarcoplasmic reticulum, SPR)
36
role of sarcoplasmic reticulum
sequester, store and release calcium at rest intracellular calcium is low in the muscle fibre, actively pumped into SPR
37
Where is action potential for muscle contraction initiated
neuro muscular junction
38
speed of release of calcium
very rapid 20-50ms to activate the thin filaments fully
39
speed of reuptake of calcium
rapid, decrease in cross brides 80-200ms
40
twitches
Low frequency of APs → twitches Limited Ca2+ release Enough time for Ca2+ reuptake/ relaxation before next contraction
41
tetani
High frequency of APs → tetani More Ca2+ is released Less time for Ca2+ reuptake Summation/ fusion Tetani sometimes used for heavy lifting Fused or sustained tetanus associated with disease
42
length-tension relationship
In addition to frequency of AP, the amount of force developed depends on the overlap between thick and thin filaments (= muscle length) prior to stimulation.
43
overlap during contraction
no overlap
44
overlap during contraction
complete overlap
45
what is length-tension relationship determined by
the number of actin:myosin cross-bride connections avaliable
46
cross bridges when the muscle is too stretched (relaxed)
less cross-bridges available = less force cant generate force directly from this position
47
cross bridges when the muscles is too contracted
all available cross-bridges occupied = no additional force possible
48
optimal length of sarcomere
overlap between myosin and actin, cross brides still available for further contraction
49
red muscles
mainly slow-twitch muscle fibres (type I fibres) can sustain small amounts of tension for long periods (resistant to fatigue) aerobic metabolism, many mitochondria and capillaries, myoglobin rich (allows us to metabolise oxygen more efficiently)
50
function red muscles
(anti-gravity/postural) – standing, walking
51
pale muscles
Pale muscles - shorter bursts of activity, less mitochondria, less myoglobin Mix of: fast-twitch (type II) : (not resistant to fatigue) -fast fatigue-resistant (type IIA) fibres -fast fatigable (type IIB) fibres slow-twitch (type I) fibres
52
fast fatigue-resistant (type IIA) fibres
enough aerobic capacity to resist fatigue for a few minutes
53
fast fatigable (type IIB) fibres
anaerobic catabolism, use glycogen, forms lactic acid
54
why are red muscles more red when it is used for more persistent exercise
more myoglobin and therefore more red
55
muscles stained light (negative) by ATPase stain
type I muscle fibres
56
muscles stained dark (positive) by ATPase stain
type II muscle fibres
57
distribution of type I and type II muscle fibres in an average person
Approximately 50:50 type I:type II muscle fibres, random distribution, similar diameter
58
type I muscle fibres
Slow contraction (50-110ms twitch time) – `slow’ myosin isoform Small force (<20g tetanic tension) - `few’ muscle fibres/MU Resistant to fatigue (oxidative metabolism, many mitochondria, good blood supply) Recruited first during contraction
59
Type IIA muscle fibres
Fast Contraction time (25-45ms) “fast” myosin isoform Intermediate force (20-60g tetanic tension) – intermediate number of muscle fibres/MU Resistant to fatigue (oxidative metabolism) Intermediate recruitment order
60
type IIB muscle fibres
Very fast contraction (<10ms)  “Fast” myosin isoform High force(50-150g)  many, large muscle fibres / MU Fatigue easily (anaerobic metabolism, glycogen store, few mitochondria) Recruited last during contraction

year 2 sem 2 motor systems (1 decks)

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