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Applied physiology > Muscles > Flashcards

Muscles Flashcards

1
Q

How many skeletal muscles does the body contain?

A

over 600

50% total body mass

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2
Q

Muscle functions

A

force production for locomotion and breathing
postural support
heat production
anendocrine organ

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3
Q

Muscle actions

A

flexors
extensors
attached to bones by tendon

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4
Q

Epimysium

A

surrounds entire muscle
connective tissue

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5
Q

Perimysium

A

surrounds fascicles
connective tissue

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6
Q

Endomysium

A

surrounds muscle fibres
connective tissue

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7
Q

Basement membrane

A

below endomysium

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8
Q

Sarcolemma

A

muscle cell membrane

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9
Q
  1. Myofibrils
A

contain contractile proteins
actin
myosin

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10
Q

Actin

A

thin filaments

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11
Q

Mysoin

A

thick filaments

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12
Q
  1. Sarcomere
A

z line
m line
h zone
a band
i band

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13
Q
  1. sarcoplasmic reticulum
A

storage site for calcium
terminal cisternae

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14
Q
  1. Transverse tubules
A

extend from sarcolemma to sarcoplasmic reticulum

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15
Q

Satellite cells

A

muscle growth and repair
divide and contribute nuclei to existing muscle fibres
undifferentiated cell
reside above sarcolemma

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16
Q

Satellite cells during growth

A

increase number of nuclei in mature muscle fibres

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17
Q

Muscle hypertrophy

A

increased myonuclei

more = greater protein synthesis

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18
Q

Muscle atrophy

A

decreased myonuclei

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19
Q

Neuromuscular junction

A

junction between motor neuron and muscle fibre

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20
Q

Motor end plate

A

pocket formed around motor neuron by sarcolemma

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21
Q

Neuromuscular cleft

A

short gap between neuron and muscle fibre

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22
Q

Role of Acetylcholine

A

neurotransmitter released from motor neuron

depolarization of muscle fibre
signal for muscular contraction to start

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23
Q

Sliding filament model of contraction

A

muscle shortening occur due to movement of actin filament over myosin filament
cross-bridge formation
actin and myosin form to create power stroke
reduction in distance between Z lines of sarcomere
head of myosin attach to actin-binding site

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24
Q

Energy for muscle contraction

A

release energy from ATP hydrolysis = energy for power stroke

myosin ATPase breaks down ATP as fibre contracts
ATP –> ADP + Pi

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25
Q

How much does a single contraction cycle shorten the muscle by?

A

~1% of resting length

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26
Q

Excitation-contraction coupling

A

sequence of events where nerve impulses reaches muscle membrane and leads to muscle shortening by cross-bridge activity

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27
Q

Fatigue

A

a decline in muscle power output due to:

decrease in muscle force production at cross-bridge level
decrease in muscle shortening velocity

depends on exercise intensity

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28
Q

Cause of fatigue very heavy exercise

A

decreased Ca2+ release from sarcoplasmic reticulum
accumulation of metabolites that inhibit myofilament sensitivity to Ca2+

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29
Q

Key metabolites contributing to fatigue

A

Pi and free radicals - modify crossbridge head + reduce number of crossbridge bound to actin
H+ - ions bind to Ca2+ binding sites on troponin = prevent binding/contraction

30
Q

Causes of fatigue moderate intensity

A

increased radical production
glycogen depletion - decrease ATP production via oxidative phosphorylation

31
Q

EAMCs

A

exercise-associated muscle cramps

spasmodic, involuntary muscle contraction

32
Q

What are EAMS caused by?

A

hyperactive motor nerons in the spinal cord

high intensity exercise = alter muscle spindle and golgi tendon organ function
increased excitatory activity of muscle spindles
reduced inhibitory effect of golgi tendon organ

33
Q

Strategies to alleviate EAMS

A

passive stretching
activating ion channels in mouth/throat = send inhibitory signals to spinal cord = inhibit overactive motor neurons

34
Q

Concentric

A

shortens/decreases
muscle contracts with force greater than resistance
dynamic

35
Q

Eccentric

A

lengthens/increases
muscle contracts with force less than resistance
dynamic

36
Q

Isometric

A

muscle contracts but does not change length
static

37
Q

Isotonic

A

muscle tension remains unchanged where muscle length decreases

38
Q

Isokinetic

A

muscle length decreases with constant velocity

39
Q

3 biochemical characteristics important to function:

A

oxidative capacity
type of myosin isoform expressed
abundance of contractile protein within fibre

40
Q

How many fibres in arm/leg?

A

45-55%
type I

41
Q

Distance runners

A

more slow twitch fibres

42
Q

Track sprinters

A

more fast twitch fibres

43
Q

What does muscle contraction speed depend on?

A

rate of crossbridge cycling
depends on myosin ATPase isoform

44
Q

Maximal power output equation

A

= force x shortening velocity

high force/fast fibres = higher power output

45
Q

What is shortening a results of?

A

changes in I band
not A band

46
Q

Functional properties

A

max force production
contraction speed
max power output
fatigue resistance
muscle fibre efficiency

47
Q

Oxidative capacity

A

number of capillaries, mitochondria and myoglobin

48
Q

Immunohistochemical staining process

A

selective antibodies binds to unique myosin proteins
fibre types differentiated by colour difference

49
Q

Muscle twitch

A

contraction resulting from single stimulus

50
Q

After stimulation

A

short latent period exist-corresponds to depolarization of muscle fibre
contraction-released from SR
tension developed due to crossbridge binding
relaxation-reuptake of calcium in SR = crossbridge detachment

51
Q

Where is speed of shortening greatest in?

A

fast twitch fibres

SR releases Ca2+ at faster rate
higher ATPase activity

52
Q

More motor units =

A

greater force

53
Q

Fast motor units =

A

greater force

54
Q

Warmup exercise results in

A

postactivation potentiation

55
Q

Each mature muscle fibre innervated by a

A

single axon

56
Q

How is muscle force increased?

A

by recruiting more motor units

57
Q

All muscle fibres that belong to same motor unit

A

same fibre type

58
Q

Motorneurons supplying large fast motor units have:

A

larger cell bodies
larger diameter axon
greater number of axonal branches
sparse afferent innervation (less spindle excitatory input)
more complex and extensive motor end plate of neuromuscular junction

59
Q

Henneman size principle

A

small slow unit = low force fatigue resistant
large fast unit = high force fatigue susceptible

60
Q

Slow motor units

A

easily excited motor neurons

61
Q

Fast motor units

A

higher threshold
harder to excite

62
Q

Frequency of stimulation

A

simple twitch
summation
tetanus

63
Q

When is speed of movement greater?

A

muscles with higher % fast-twitch fibres

64
Q

When is max velocity of shortening greatest?

A

at lowest force
true for slow and fast fibres

65
Q

Muscle force-power relationship

A

peak power generated greater in muscle with higher % fast-twitch fibres

peak power increases with velocity to 200-300 degrees/sec
decreases at higher velocities because force decreases with increasing movement speed

66
Q

Formation of cross-bridges is triggered by

A

calcium binding to troponin

67
Q

Amount of force exerted dependent o

A

type of motor unit recruited
initial length of muscle
nature of neural stimulation

68
Q

Voluntary muscle contraction first step

A

innervating alpha-motor neuron reaches an action potnetial

69
Q

Influence muscle fibre type on force velocity curve

A

peak power generated greater in muscle containing high % fast fibres
compared to muscle contain high % slow fibres

70
Q

Myonuclear domain

A

region of the sarcoplasm surrounding an individual nucleus

importance = single nucleus responsible for gen expression for its surrounding sarcoplasm

71
Q

NMJ trainable of fatigue

A

increase size
increase number synaptic vesicles
increase number ACH receptors on post-synaptic membrane

72
Q

Shortening of the muscle will continue as long as?

A

ATP energy available
Ca2+ free to bind to troponin

Applied physiology (24 decks)

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