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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
How much does a single contraction cycle shorten the muscle by?
~1% of resting length
26
Excitation-contraction coupling
sequence of events where nerve impulses reaches muscle membrane and leads to muscle shortening by cross-bridge activity
27
Fatigue
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
28
Cause of fatigue very heavy exercise
decreased Ca2+ release from sarcoplasmic reticulum accumulation of metabolites that inhibit myofilament sensitivity to Ca2+
29
Key metabolites contributing to fatigue
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
Causes of fatigue moderate intensity
increased radical production glycogen depletion - decrease ATP production via oxidative phosphorylation
31
EAMCs
exercise-associated muscle cramps spasmodic, involuntary muscle contraction
32
What are EAMS caused by?
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
Strategies to alleviate EAMS
passive stretching activating ion channels in mouth/throat = send inhibitory signals to spinal cord = inhibit overactive motor neurons
34
Concentric
shortens/decreases muscle contracts with force greater than resistance dynamic
35
Eccentric
lengthens/increases muscle contracts with force less than resistance dynamic
36
Isometric
muscle contracts but does not change length static
37
Isotonic
muscle tension remains unchanged where muscle length decreases
38
Isokinetic
muscle length decreases with constant velocity
39
3 biochemical characteristics important to function:
oxidative capacity type of myosin isoform expressed abundance of contractile protein within fibre
40
How many fibres in arm/leg?
45-55% type I
41
Distance runners
more slow twitch fibres
42
Track sprinters
more fast twitch fibres
43
What does muscle contraction speed depend on?
rate of crossbridge cycling depends on myosin ATPase isoform
44
Maximal power output equation
= force x shortening velocity high force/fast fibres = higher power output
45
What is shortening a results of?
changes in I band not A band
46
Functional properties
max force production contraction speed max power output fatigue resistance muscle fibre efficiency
47
Oxidative capacity
number of capillaries, mitochondria and myoglobin
48
Immunohistochemical staining process
selective antibodies binds to unique myosin proteins fibre types differentiated by colour difference
49
Muscle twitch
contraction resulting from single stimulus
50
After stimulation
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
Where is speed of shortening greatest in?
fast twitch fibres SR releases Ca2+ at faster rate higher ATPase activity
52
More motor units =
greater force
53
Fast motor units =
greater force
54
Warmup exercise results in
postactivation potentiation
55
Each mature muscle fibre innervated by a
single axon
56
How is muscle force increased?
by recruiting more motor units
57
All muscle fibres that belong to same motor unit
same fibre type
58
Motorneurons supplying large fast motor units have:
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
Henneman size principle
small slow unit = low force fatigue resistant large fast unit = high force fatigue susceptible
60
Slow motor units
easily excited motor neurons
61
Fast motor units
higher threshold harder to excite
62
Frequency of stimulation
simple twitch summation tetanus
63
When is speed of movement greater?
muscles with higher % fast-twitch fibres
64
When is max velocity of shortening greatest?
at lowest force true for slow and fast fibres
65
Muscle force-power relationship
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
Formation of cross-bridges is triggered by
calcium binding to troponin
67
Amount of force exerted dependent o
type of motor unit recruited initial length of muscle nature of neural stimulation
68
Voluntary muscle contraction first step
innervating alpha-motor neuron reaches an action potnetial
69
Influence muscle fibre type on force velocity curve
peak power generated greater in muscle containing high % fast fibres compared to muscle contain high % slow fibres
70
Myonuclear domain
region of the sarcoplasm surrounding an individual nucleus importance = single nucleus responsible for gen expression for its surrounding sarcoplasm
71
NMJ trainable of fatigue
increase size increase number synaptic vesicles increase number ACH receptors on post-synaptic membrane
72
Shortening of the muscle will continue as long as?
ATP energy available Ca2+ free to bind to troponin

Applied physiology (24 decks)

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